PV upgrade year 1 results

It's been a year since we upgraded our PV system. We re-roofed our house and I thought it would be good opportunity to review the pros and cons of upgrading. We had a 1.1kW Kaneka thinfilm system with a 1.7kW SMA inverter, with some room for more panels. We are lucky enough to be getting the 40 cents Feed in Tariff (FIT) on top of the miserly 8 cents Synergy pay us for any power fed to the grid. So, my main thought was what will our power bills be after the FIT ends in mid 2020? Based on the current power prices (+5% price rises) they actually worked out to be quite high, mainly because of the low price for power fed to the grid. It would be nice to think that common sense would prevail in this area (eg parity with prices we pay them), but I doubt this will happen any time soon. Anyway, I'm not a big fan of paying bills, especially thinking of the future when I'm retired. So we looked into an upgrade.

I got some quotes and advice on upgrading. It turns out you can keep the FIT as long as you keep your original inverter. It also turns out that you can overload most inverters and we decided to upgrade to a 3.1kW system. The panels are REC 260PE's, with six facing due North and six facing due West. Spreading them in two orientations means that we will also use more PV power in the home, which is best post FIT. The system cost $4,650 installed with new racking, etc. We were lucky enough to sell our old Kanekas for $900 to someone who wanted to expand his system and needed the same panels to be compatible with the existing ones. All up this took the price to $3,750. Here are the first year's data:

To sum it up we had a yearly bill of -$612 (credit), the Business as Usual (BAU) bill (ie no PV) would have been $630 so we saved $1,242. This makes the payback time roughly three years, after that we'll have three more years of FIT and then we'll still have small to negative bills for the next 25-40 years. Apart from the economics, getting more PV is better for the planet too. Remember, business as usual is not an option if we are to keep the planet from cooking...

Here's the N facing set:

And the West facing set (on the garage roof):

Overall we're chuffed with the new system. Comparing the old system's generation to the new one is interesting. Theoretically a 3.1kW Kaneka setup would have generated 11.9kWh/day (based on last 6 year's data) compared to the 9.7kWh of the new system (although our roof would not be large enough!). I think the reason for this is threefold. Firstly, I think there is something the experts call clipping happening. This is when the panels generate more power than the overloaded inverter can handle and some power is wasted. Secondly, the West facing panels would be generating less power than the North facing ones due to low morning generation. Thirdly, I think the Kaneka panels are better suited to Perth's heat and produce more power than mono and poly crystalline panels. I have seen this effect at our local Primary school where two systems side by side are located. The smaller thinfilm system (2kW) produces significantly more power than the larger (2.3kW) monocrystalline system.


That's all folks. Food for thought if you're in the same boat as us.

New PV system

We first got PV (photo voltaics or solar power) 6 years ago and the 1.1kW system has done us well. We recently had a new roof put on so we had to remove the solar panels and I thought it might be a good idea to upgrade our PV system at the same time. This is how the old system looked.

The 1.1kW system cost us $6,500 and in 2010 we qualified for the new WA Feed in Tariff (FIT). This pays us about 48 cents a kWh that we feed to the grid. The FIT runs for 10 years to 2020. A while ago our energy provider (Synergy) decided to reduce the amount they paid people who don't get the FIT for power fed to the grid from parity to what they charge their customers (28 cents) to about a third of parity (8 cents). That got me thinking, when the FIT ends what will our power bills cost us? The amount shocked me, about $600 a year for us measerly 5kWh a day users. I thought well I'll just upgrade my system in 6 years time and we'll be right. Then I thought wait a minute, why don't we upgrade now and the new, bigger system will pay itself off much more quickly with the FIT. I checked the rules which state that you can keep the FIT if you keep your original inverter. Luckily we got a larger inverter than our system required, a SBA 1700 which allowed for a bigger system.

So, now to choose new panels and sell the old. I thought it would be hard to sell the old Kaneka thin film panels considering new panels sell for under $1 a watt these days. However I was pleasantly surprised when an ad in Gumtree got many people interested. The first offer was $900 for the 1.1kW Kanekas, an offer I couldn't refuse. It turns out that the buyer wanted to upgrade his own system and needed that vintage Kanekas to be compatible with his other panels.

 We were told that we could overload the inverter by placing some panels facing west and some north, so we decided on around a 3kW system. The choice of panels was between Yingli, Daqo and REC. The first two are good quality chinese panels, the third very good quality European. We decided on the RECs which should give better performance over a longer period of time and have a world leading energy payback time of one year. The REC 260PE polycrystalline panels are now installed in two strings of 6 panels, giving us 3.12kW. This is the west facing, tilted array on the garage roof.

And here's the North facing array with the solar hot water system alongside.

This upgrade cost us around $4,600 including removal of the old panels. Subtract the $900 we got for the old panels and the total cost was $3,700. It should pay itself off in about three and half years and then we'll have another two and a half years of FIT before we go back to the stingy rate. Our power bills will be in the negative (ie a credit) for the foreseeable future so the money is a great investment as well as good for the environment. Despite being bigger in kW, this system is much smaller in physical footprint and this allowed us to move the solar hot water system further up the roof into a less shady spot.

Now, let the sun shine all day and the rain come at night...

Power year 6 and PV payback times

Our 1.1kW PV system is in its sixth year and still going strong. Power generation dipped slightly and unfortunately our consumption went up a bit. We still use about a third of the WA average though so not too bad.

On the money front we saved nearly $600 off our bill, partly thanks to our low usage and also the fact that we feed in over thirds of our generated power to the grid (the generous feed in tariff helps here).

It's been 6 years now since we installed our solar panels. In that time our PV system has saved us $3,104 off our power bills. That means we're half way to paying off the cost of the system (our 1.1 kW Kaneka/SMA system cost $6,460 after rebates back in 2008). Solar panels are way cheaper nowadays but the rebates and feed in tariffs are less favourable as well. We paid a lot for our system but are lucky enough to be paid 49c per kWh fed to the grid and this is guaranteed to 2020 (if the government keep their promise!). In fact I've just worked out that I'll need to buy more solar panels in 2020 otherwise my bills will go from small to fairly big. The last yearly bill would have been $493 feeding power in at 8.5 cents a kWh instead of $58! Adding more panels will be hard for us since our unshaded roof space is almost full of thin film panels, we may even need to try to sell the panels and get a whole new set of less space hungry panels...

Despite less favourable rebates and feed in tariffs these days PV is still a great investment. The table below shows estimated payback times for people in Western Australia. As you'll see huge savings can be made over 25 years and most PV systems will last up to 40 years. The payback time may be shorter for smaller systems but this is not the whole of the matter. Bills will be less with bigger systems meaning that overall savings are far greater in the long run.

Power prices have almost doubled in the last six years in WA, so now is a great time to buy PV. If you orient some panels to the east, north and west you'll maximise your use of generated power, which is a big plus under current feed in rates (8.5 cents a kWh in WA compared to 27 cents for power bought from the grid).

I'd love to hear from people about their experiences with PV and if anyone has questions on this topic please fire away.

It pays to read the meter

I read our meters once a week. Now some people (or most?) would think that's obsessive or just plain weird, but it does give me a good idea of when something's not right. For example if I get a spike in power use I think "did I (or Amy, more likely) forget to turn off the hot water booster"? If water use is high I wonder whether the retic settings need adjusting.

My meter reading paid off recently. About a month ago our water use spiked in a big way, using 2,000 litres a day. The mains meter kept spinning despite the rainwater tank being full and it had us stumped for a while. At last we found the leak, a faulty solenoid is causing the retic in a hidden spot to run 24/7. It's fixed now and what a relief.

Most people wouldn't realise until they get the water bill and even then they might not twig. It just goes to show that there's some method in my madness...

End of year stats

Well, another year has come and gone. We'll be away for the next two months, so I thought I'd get this out before we left.

Gas and electricity use is up a tiny bit this year. I can't tell what the reason is, but it seems to be due to electricity use rather than gas. Since we've had solar hot water our gas use has dropped from 16kWh a day to between 8 and 9.5kWh.

The chooks are laying less, we're on course for 1,000 egss after 1,400 last year. One of our old Australorps died this year and the old girls are definitely laying less. It also seems that our Hi-lines are laying less. They are one year old now, so I'm a bit surprised at this.

Transport has been a winner this year. I've been riding the Fr8 to work three times a week most weeks. Our aim of halving our car kms from 2010 levels hasn't quite succeeded, but we're on course for 10,000kms this year which isn't too bad.

That's it for now. We're off to Europe to blow our carbon budget for the next few years! But this is the topic of another post...

Have a safe and sustainable Christmas.

Beware aircon use this summer

We don't have aircon at home, but Amy's parents do. Amy's Dad diligently records their power readings once a week. Each year I input their PV data to show them how much power they generate and consume. They're pretty good, consuming between 6 and 9 kWh a day on average. Inputting the data this year I saw what I thought was a mistake, a reading that just couldn't possibly be right. Then I looked into it and saw a comment, "heat wave". This made me wonder and I checked with Neil. Yes indeed, the heat had been so bad in late December 2012 that the aircon was on 16 hours a day! Power consumption went through the roof, as you can see.

A whopping 48 kWh a day! Another heat wave in February saw jumps to 20kWh a day too. Now I'm not going to preach about the use of aircon, lots of people have it and that's fine. It's not my cuppa tea, but if you do use it then beware that it will cost you. 50kWh a day equates to $12, that's $85 a week more or less. It also obviously costs the planet in carbon emissions and it costs other power consumers too. At peak times the wholesale price of power goes through the roof, so the more that is used in these times pushes power prices up to everyone. So, here are some tips to minimse your use of aircon:

Turn it up. If you set the thermostat higher (say 23-25 C) you'll use much less power and you'll still be comfortable.

Go outside every now and again, you might just find that a lovely sea breeze is in and you can open up the house and turn off the aircon.

Do the flush. We do this all the time in summer. At night open up the house to let cool breezes in; first thing in the morning we shut up the house on hot days and close curtains, etc. This way we trap the cool air inside and stop heat getting in. Then open up the house when a breeze comes in and it's cooler outside than in.

External shade on east and west facing windows is essential in summer. This is the best and easiest way to stop your house becoming a green house!

Turn on ceiling fans, they use little power and can make rooms feel five degrees cooler than they actually are.

Good luck keeping cool this summer, here's hoping that we don't get too many heat waves...

A real winter (for a change)

Anyone who lives in Perth would know that we've had a lovely wet winter, just like they used to be. I've even caught myself thinking that I wish we'd have a few dry days to do the washing! Here's a chart of the rainfall on our block in the last four years and a bit.

Our rainfall year goes from mid July since we installed the rainwater tank at that time of year. As you can see we've got off to a great start to the year after a poor June (end of year 4). The tank has been full enough to supply all our needs since May 5th, which means we may be 'off grid' for about 30 weeks this year (a record for us).

It feels good not to be taking water from the grid, since Perth's dams are still only at 36% capacity despite all this rain. Streamflow has dropped from 400GL a year pre-1975 to around 100GL a year these days, which means the dams simply don't fill up now. Two thirds of Perth's water are from what I'd call unsustainable sources (desal 23% and groundwater 46%), so to be using rainwater (a truly sustainable resource) is great for us and the general community.  

Here's hoping that it keeps raining and the dams overflow...

Rain water harvesting year 4

It's been four years since we installed our 14,000L rain water tank, so here's the annual wrap. It was another dry year in WA, with 571mm on our block. Perth's average is supposed to be around 750mm, but the new reality is much lower. Here is the rainfall in the last four years, recorded by me on a daily basis. You can see we have a very seasonal pattern, with most rainfall in the cooler months (April to October). The average for the last four years is 634mm and we've only reached 750mm once.

Despite this we harvested and used a record 81,241L of rainwater this year, which represents 30% of our total use. This is pretty good going I think for a 14,000L tank. It means we've got through almost six tanks worth in the year. The key to this is the fact that everything is plumbed in to the tank (house and garden), so we minimise our losses to overflow by using rainwater whenever it's available. The water switch switches back to mains water when the tank is empty and switches back when it fills up.

This chart shows weekly rainfall (scale on the right axis) and our daily consumption (left axis) split into the proportions of tank and mains water (green and red). It shows the long dry period through summer when there is little rainwater available and when our consumption rises to keep our fruit and veg going in the intense summer heat. We go about 6 months of the year using predominantly rainwater.

The next chart shows how the tank level fluctuates with rainfall and usage patterns. The level stays high in winter with good rainfall and low usage, but as soon as rainfall drops and we turn on the retic the level drops sharply.

The last chart below shows our daily consumption of both rainwater and mains water for the last four years. You may think that for a sustainable minded family we use too much water (734L a day this year). I know it sounds like a lot but it's actually lower than the Perth average. In our defense we use little in the house (about 200L a day) and lots on the garden. Perth has extremely hot, dry summers and this means it takes lots of water to keep the garden going. We have 20 fruit and nut trees, lots of veges and a small lawn on our 700 sq.m block. Also, we've cut our water usage despite adding more retic to more plants recently.

Next year we hope to use a lot less too. We have just bought a new front loading washing mashine to replace our old top loader. It uses 62L per wash as opposed to about 180L, so we could save 25,000L here. And our new grey water system should save us lots, especially on the lawn. Another big saving here and we could use 50,000L less next year. I'm predicting water use of 600L a day next year. Watch this space...

Going green: what's the payback?

Going 'green', or installing technologies which lower your footprint, is mostly done by people who are interested more in saving the planet than saving a dollar. This certainly applies to us. The perception for many is that being green is more costly, so I thought I'd show you how going green has lowered not only our ecological footprint but also our bills.

When we recently installed a grey water system it made me reflect on all the things we've done in the last five years. These include solar PV, rain water harvesting, solar hot water, cargo bikes and grey water. I added up the costs of the above and it came to $33,500, which is a lot of money. But how much will these technologies save us in the long run? Well, here are my best estimates:

system	cost		savings per year		payback (years)
PV	$6,500		$600		10.8
solar hot water	$3,500		$300		11.7
rain water	$10,000		$100		100.0
grey water	$4,500		$50		90.0
cargo bikes	$9,000		$5,000		1.8
Totals	$33,500		$6,050		5.5

There are some surprises in there and I'll explain each one.

First, PV. We have a 1.1 kW Kaneka thin film solar PV system. It generates more or less what we consume (4.5 kWh a day) and we feed in 75% of what we generate to the grid. We are lucky enough to qualify for a now defunct feed in tariff, which means we get paid 48 cents a kWh for power fed to the grid. This makes our bills around -$60 a year (credit) and our bill would be around $550 a year without PV, so we save around $600 a year. This means the system will pay itself off in about 11 years and after that we'll be saving money for another 15-30 years. This was obviously a good investment of $6,500.



Our solar hot system (a Solahart 180L thermosiphon system), cost $3,500 two and half years ago and it saves us around $300 on our gas bill. We boost a little bit between May and October, but this only costs us $20 a year in electricity. The payback time is very similar to PV.

Water is so cheap in WA that there is no way our rain water or grey water systems will ever pay for themselves. Both systems were quite expensive ($10,000 and $4,500 respectively). The 14,000L tank needed lots of digging and piping, new gutters etc to install and is piped into everything (whole house and retic). The Grey Flow system was less expensive and feeds a lawn and fruit trees.We harvest 70,000L of rain water a year and probably about 50,000L of grey water and you can see that the savings aren't great. However this isn't a big deal for us since we see these technologies as more of a society benefit than anything else. The more water we can generate the more water there will be in the dams and the less the need for desalination and ground water use (and the less power used to pump them around).







The bikes have almost paid for themselves already. How can that be I hear you say. Well thanks to the bikes we got rid of our second car, which cost us at least $5,000 a year to run. These are not your average bikes, they're both electric cargo bikes (one is a Bakfiets long, the other a retrofitted electric Workcycles Fr8). They're dutch and they'll probably last longer than me. They get us to work, to the beach, shopping, school runs and more.

So the payback time for all this is five and a half years, not bad eh? Obviously payback times will be different for everyone, depending on the costs and savings involved. However this shows quite clearly that going green can save you lots of money, especially if you invest in areas where you get the best bang for your buck.

Solar year 5

It's five years since we installed our solar PV system (a 1.1 kW Kaneka thin film grid connect system). Ever since then our goal has been to generate more power than we consume and after four years of achieving this we have not met our goal this year. The pattern of usage and generation was very similar to past years, with higher consumption and lower generation in winter, transitioning into higher generation and lower consumption in the warmer months.

We came pretty close to our goal, generating just 44 kWh less than we consumed (about 10 days worth of generation). Although we took a lot from the grid, we also fed in three quarters of the power we generated to the grid. We are lucky enough to qualify for the 48c feed in tariff (FIT) so this makes our bill really low (a credit of $67!). If we didn't have solar panels (BAU, business as usual) our power bill this year would be $552 which means we saved $619 this year. Since our panels cost around $6,000 five years ago this means the payback time will be roughly ten years, which isn't too bad considering we should get another 15-30 years life out of them. We saved a grand total of 46 cents with smart power this year. This is a system whereby you pay different tariffs depending on the time of day you take power from the grid. There is very little point in having it now if you get the FIT but we'd need to pay $60 to remove it so there's no point right now. 

kWh generated	kWh taken from grid	kWh fed into grid	kWh used	Average daily usage (kWh)	Average daily generation (kWh)	Year 5 bill	BAU bill	$ saved with smart power	% of power generated fed to grid
1619	1281	1237	1663	4.57	4.45	-$67.34	$551.89	$0.46	76.4

So why did we use more power than we generated this year? There are a few reasons. As solar panels age their production tends to drop off slightly and this is one of the reasons we didn't meet our goal this year. The chart below shows our average daily generation and usage in the last six years. Our generation has gone from 5 kWh in year 1 to 4.7, 4.8, 4.5 and 4.45 in subsequent years. As a matter of interest here are the average daily amounts of power generated by our system each month over the last five years. Being in the southern hemisphere means our summer is December to February and this is when we generate the most. Spring is the next best season, then autumn and winter last. The main reason for this is the number of sunny hours per day which is highest in summer. Perth has a mediterranean climate, with hot dry summers and cool, wet winters. This means that winter days are often cloudy which leads to low solar radiation (and they're also shorter of course). PV panels actually perform at lower efficiency above 26C, which we regularly get in summer. So this means that the longer and sunnier days in summer more than make up for the lower efficiency of the panels in high temperatures. We also get some shading of our panels in winter, which helps explain why June and July are so bad.  

Our usage has gone from 6 kWh in year 0 (before we went solar) to 4.7, 4.4, 4.3, 4.5 and 4.6 in subsequent years. We've done really well in past years to use less power despite adding new power users (eg solar hot water booster, rain water tank pump, electric bike charging) but this year we simply couldn't do it. We bought another electric bike (the Fr8) and recently installed a grey water system which uses a small amount of power to pump the water out. These two additions coupled with lower generation this year made it too hard a task. We still did very well considering the average usage for WA is around 18 kWh a day, four times what we used.

But never mind, we're hoping to turn this around next year. Our 15 year old washing machine just died so we've bought a new super efficient front loader to replace it. This may make the difference next year so watch this space.

PV payback time: Is it still worth it?

PV (photovoltaics) have become very popular in Australia recently due to generous government incentives. These incentives (such as feed in tariffs) have now all but gone. So the question is, is it still worth installing PV? Well the answer is a definite yes and I'll tell you why.

In Australia most electricity providers are ripping people off when they feed power back to the grid. They charge customers around 25 cents a kW and pay them about a third of that for power fed to the grid. This means there's no great incentive to feed power into the grid but it doesn't make PV uneconomic. I've updated my payback calculator spreadsheet and come up with the following numbers:

Price	$2,000	$2,500	$3,000	$3,500
System size	1 kW	1.5 kW	2 kW	2.5 kW
% generated fed into grid	50	67	75	80
Payback (years)	6.1	6.1	6.1	6.1
10 year average annual bill	$981	$899	$816	$733
25 year average annual bill	$1,441	$1,315	$1,190	$1,064
BAU average annual bill (10 years)	$1,307
BAU average annual bill (25 years)	$1,935
25 year savings	$12,353	$15,503	$18,628	$21,778
25 year savings minus outlay	$10,353	$13,003	$15,628	$18,278
Assumptions: 775 kW from PV used in home per year, 1550 kW generated from a 1kW system per year, 10 kW is overall consumption per day. Price rises of 5% per year, feeding power in at 8.5c per kWh, paying 25c per kW and a daily service charge of 45c. NB: Payback time is independent of annual bills, but annual bills are a big factor in your choice of system. Payback calculated by subtracting 10 year average bill from BAU 10 year average (10 year average annual saving), then dividing the cost of system by this average. The savings made relate to the value of the power your panels generate, costed at either 25c per kW if you use it in the home or 8.5c per kW if you feed to the grid.

Sorry, the formatting of the table didn't come out too well, but you should be able to get the drift of it. BAU stands for business as usual, or the price you'd pay if you didn't have PV. The prices for PV systems are based on ones I've seen advertised at Energy Matters. Power prices are based on current WA tariffs, assuming a 5% rise per year. Please note that these calculations are just a rough guide and will vary depending on your electricity provider, the power you use and the time of day you use it, the amount of power your panels generate and the price of the installed system.

What's interesting is that larger systems are still better in the long run, despite the fact that power fed to the grid is poorly priced. The payback time is the same, but savings over 25 years are higher. The essence of this table is in the savings you make, which range between $414 and $731 a year over 25 years.  A relatively small investment now (eg $2,000) will give you a high return (eg $10,353). If you put it in the bank it would earn $4,450 at 5% compound interest (if the banks don't go bankrupt in the meantime!). And I haven't even mentioned the other benefits to society, such as greenhouse gases abated and water saved.

But I'm going to move house some day I hear you say. Don't worry, PV adds value to your house and makes it easier to sell so you'll make your money back anyway.

So if you're thinking you've missed the boat on PV then think again. Sure, the payback time has risen since the scrapping of feed in tariffs, but power prices are going to keep rising and I certainly wouldn't want to go into retirement without panels on my roof. By the way, most solar panels can last for 40 years.

2012 eggs

We ended the year with 1,386 eggs laid. This was a great result, our best to date. Of course we couldn't eat this many eggs, but it's great to give them away, barter them or sell a few every now and again.

We now have seven chooks, four Hi-line browns and three Australorps. The Hi-lines are about a year old and in their prime, whereas the Australorps are about 4 years old now. In year one the Australorps laid well but since then their production has dropped off and they're often broody. They still lay the odd egg, but I'd say that they lay about 1 a day between them whereas the Hi-lines lay 3 a day between them on average. It's early days for the hi-lines but if they keep their laying up for a few years I'd have to say that they're the best backyard layers for the burbs. Since we can't keep roosters and breed chooks there doesn't seem much point in having heritage chooks, except for their beauty and interesting looks. I love Australorps but their broodiness is a big issue. Auracanas are great for their blue eggs but they don't live that long from our experience.

The new chooks arrived at the end of January and started laying almost immediately. They laid well through autumn and there was the usual dip in production in winter, although this was much less marked than in previous years. Then they cranked up in spring and have been laying a bit less in summer. We'll keep an eye on the production from the Australorps, Lacey, Snowy and Splash. Hopefully they'll keep going a while longer so we don't have to make the tough decision over whether to keep them or not...

2012 transport

This time last year we got rid of our second car and in the middle of the year we got a new electric cargo bike (a Workcycles Fr8). I predicted that we would cut our daily kms by car by 10km a day and increase our kms by bike by the same amount. The predictions turned out to be right in one case and a bit out in the other.

We ended the year averaging 29km a day by car compared to 41km a day last year. After years of trying to reduce our car use I'm pretty chuffed with this. It equates to 5,000 km less over the year. In terms of fuel costs alone we saved approximately $1,000. If you include the lower cost of running one vehicle instead of two for the year then we've saved a minimum of $6,000 which equals most of the money we've spent on our two bikes. Next year we'll pay off the cost of the bikes altogether and we'll be saving money from then on.

The kms by bike went from 9 to 14 kms a day. This means that not all the kms reduced by car were replaced by bike travel. This is because sometimes we used public transport instead. I'm sure next year we'll do more kms by bike since we'll have the two bikes going all year. The Fr8 does more kms than the Bakfiets (81kms a week against 36kms a week in the last six months of the year) because I ride it to work a couple of times a week whereas the Bakfiets does more local trips to school, shops, etc. I much prefer riding to work than driving or taking public transport. It's quicker than the bus and less stressful than driving.

The big picture is that our carbon emissions have dropped considerably in the last year and hopefully a few people have been inspired to do the same. I certainly see a lot more cargo bikes on the road.

So get out there on your bike, YOU can do it too.

Rain water harvesting year 3

We've had a pretty good year of rainfall, with 691mm. This is about the average for Perth these days. Last year we had 515mm, the year before 757mm. We harvested and used 77,000L of rain water with our 14,000L rain water tank, which is the most to date.

29% of our water use was rain water this year, which is way up on the 21% of the previous two years.The chart below shows the weekly figures for rainfall (right axis) and water consumption (left axis), with the proportions of tank water (green) and scheme water (red) used. Rainfall in September and November to January allowed us to harvest more in this period than in previous years. Also, the pump broke down less often this year, which always helps.

This next chart is a new one and shows the level of the tank (left axis) and weekly rainfall (right axis). As you would expect the tank is fairly full in winter (june-august) and still has water right through spring. Then as rainfall drops off the tank empties as we turn on the retic to water our vegies and productive trees. Through most of summer the tank was empty until the return of rain in April. Since then we've had water in the tank most of the time. In May we had a warm, dry spell and turned the retic back on. This emptied the tank, but soon after the tank refilled. This shows the value of having the tank plumbed into everything (house and garden) since we're using as much of the rain water when it's available. If we had a few appliances (eg toilet and washing machine) running on tank water and the rest on scheme as is common, then we wouldn't have used much of the water in May. When it rained again a lot of that rain water would have been lost to overflow. I estimate that we would use about half or a third the tank water we currently use if we only plumbed in a few appliances. This highlights the need for people to plumb tanks properly to maximise the benefits to themselves and the broader community.

Best of all, we cut our water usage by 100L a day this year. We did this despite adding yet more retic (out the front on our productive trees). I can't really explain this. It could just be that we had less dry spells when we needed to turn the retic on (about 70% of our water usage goes on the garden). 

Hi-line = high production

It's been 4 months since we got four new Hi-line brown chooks. These hybrid hens have been bred for the sole purpose of pumping out eggs regularly and by heck do they do a good job of it. It took them a few weeks to get going but since then this has been the result most days. 

We have seven chooks now (we off loaded our two Wyandottes to a breeder a while ago), but our older girls (Australorps) are not laying at all now. This means our new girls lay an egg a day almost every day! You can see from the chart below that production is picking up markedly.

This has meant our cumulative total is running well above all previous years and should easily surpass our best ever year.

Now we're wondering what to do with our old girls. They're almost four years old now and they're not laying. They may come back into lay in the spring but we are paying a fair bit for food with no gain in eggs right now. We obviously have an emotional attachment to them, but they do need to pay their way a bit.

On another note, today is a joyous day. After searching the web far and wide with no success I have now found an easy, quick way to put Excel charts in the blog. Up until now I have been printing charts, then scanning them and saving them as jpegs before importing to blogger (what a pain in the arse). Now I've found a much better way. A brilliant geek by the name of Jon Peltier has developed an Excel add-in to export a chart as a png file. All I have to do now is highlight a chart, click on the add-in and it exports it to wherever you want to put it. Then you go to blogger and import the png image. It's so easy, I love it. The best bit is that it's free, download the export chart zip here and install the add-in.Thank you Jon, geek c'est chic! 

Solar year 4 ends

Phew, we made it! Every year we aim to produce more power with our PV system than we use at home. Normally we achieve this some time in February, 3 months before the end of our 'solar year'. This year we only made it with 1 week to go, having produced 13 kW more than we consumed (see chart below). The lines starting at the top are the running average of  power generated by our 1.1 kW Kaneka thin film system. The lines starting at the bottom are the averages of power used and the point where the two lines meet is where we break even.

Our other target is to reduce our electricity usage each year and unfortunately we didn't make it this year, missing out by  40 kWh (or about 9 days worth of power use).This breaks our run of 3 years straight of lower usage than previous years (6 kWh to 4.7, to 4.4, to 4.3 kWh per day). Last winter was our first year of  having solar hot water and this would have been a factor in our higher electricity usage this year. Our hot water system has an electric boosting system and I did a rough calculation that this used about 100 kWh over the cooler 5 months of the year. This equates to around 0.3 kWh a day over a whole year, so that would explain why we didn't cut our usage this year. The TV still only comes out once a week, but I don't think this has made much difference since we just use the computer more now. Still, we don't feel too bad about our consumption since it's a quarter of the average household in WA.

Solar generation was lower than any previous year, which I expected since we had a rainy, cloudy winter last year. I'll take rain over kWh any time thanks. Another factor in this would be that PV systems tend to lose some efficiency over time. We generated 4.5 kWh a day this year, after 5 in year 1, 4.7 in year 2 and 4.8 last year.

We followed our normal pattern of higher usage in winter, coupled with lower generation. The lines cross in spring when we begin to generate more power than we use. The annual bill won't break the budget this year, we got a credit of $94. Without PV we'd be up for a bill of around $500, so we made a $590 saving. For the first time we lost money with Smart Power this year (Smart Power is when you are charged a different tariff depending on the time of day you buy power in). This was because this was the first full year under the feed in tariff and there's a flat rate of payment for power fed to the grid (47 cents for us). We used to save a lot with Smart Power, mainly due to feeding lots of power into the grid at peak periods. Again, we fed in around three quarters of the power we generated. This was great for the bill since we qualify for the feed in tariff.

Another solar year gone, I can't wait until I have 20 years of data to play with...

Chooks year 3

 By now you know I like collecting data, but I bet you'll think I am totally obsessive compulsive when you hear that we've been counting our eggs for the last 3 years. But aren't the results fascinating?! My spreadsheet 'Eggsactly' has shown us that: older hens lay less; hens lay less eggs in winter in Perth and; heirloom chooks suck when it comes to egg production! Below is Holly, one of our Golden Laced Wyandottes and our Australorps Snowy, Martha, Splash and Lacey.

In year 1 we averaged 2.7 eggs a day, in year 2 this dropped to 2.1 and last year it dropped to 1.5 eggs a day. Our flock numbers have declined a bit over the years, but age is an obvious factor in the drop in egg production. Most of the hens were around 6 months when we started taking stats, which means they are now around three and a half. This year has been disappointing and we've come to the conclusion that we need new blood in our flock to re-invigorate it and increase our production. As vegetarians we rely on eggs a lot for protein and of course you just can't beat a fresh, free range, home laid egg. We've have had some problems getting our broodies to sit on fertile eggs, but we just put batch number 3 under Lacey and we're hoping it will be third time lucky. The breeds we now have are Australorp (3) and Wyandottes (2), which are heirloom breeds. They are beautiful hens and I'd still like to keep a few for interest, but our new chooks will be hybrid Hi-line crosses which will hopefully lay loads of eggs for us.

Seasonality is another big factor in our egg production. The averages by season for all three years are 2.5 eggs/day for summer (December-February), 1.7 for autumn (March to May), 1.1 for winter (June to August) and 2.7 for spring (September to November). So despite extremely hot summers and relatively mild winters hens struggle in winter and do well in summer. This highlights the need to give your chooks really good insulation (which we haven't done yet) and good solar access. I'd like to add an extra layer of tin above the roof of our hen house and put in aircell insulation and some insulation batts at some stage. Ideally we'd make a solar passive chook yard, but we don't have room for that unfortunately. Check out this cool 'Chookship' Hilton Harvest are building for their chooks. It's made with used tyres rammed with adobe for high thermal mass. This will be rendered and enclosed with North facing windows to catch and store warmth in winter:

We're hoping for some very happy, productive chooks at HH. This might be a bit OTT for the backyard though, unless you happen to have a gang of keen, fit Woofers to give you a hand...

Solar hot water year 1

It's been a year now since we got a solar hot water system. As is my wont, I took weekly readings of our gas meter and set up a spreadsheet (gas-o-lean) to see what was happening. So here's the dirt: we cut our gas use by two thirds in one year! We also cut our gas bill from $470 to $200.

Our old hot water system was a 90L gas storage. It was fairly old and cladding the dunny wall would have been pretty hard with the tank in the way. So I looked in to the alternatives. Wood is a good sustainable option for combined heating and cooking and hot water, but it's not that easy or cheap to get wood in the city and we don't have much space for storing it. It also doesn't seem practical in Perth's hot climate, where lighting a fire in summer for a bit of hot water seems crazy. The next option we considered was instantaneous gas (IG). I'd been told that for low hot water users such as ourselves this might be best when taking into account the embodied energy aspect. This means that although more energy is used to heat water via IG than via solar, the larger embodied energy in solar systems can mean they are less sustainable than they appear (the energy used to manufacture solar systems takes a long time to be paid back by the solar generation). The last option we looked at was of course solar, which is a popular choice for many in one of the sunniest cities in the world. This seemed like an obvious choice for us since we run our house on PV power and because it's renewable. It drives me somewhat crazy when people almost talk of gas as renewable (just because it's cleaner than coal doesn't make it clean!). Solar just makes sense to me, you pays your money and you forget about it for 25 or so years. So despite some advice to the contrary we opted for solar.

You'll see in the photo above that we oriented the panel in landscape rather than the normal portrait fashion. This was because our roof has two pitches, with the upper two thirds steeper than the lower third. We wanted to get the panel at the steeper pitch because this maximises solar radiation in winter, which in Perth (as in most places) is when you get the least sunshine. The lower angle of the sun in winter means you need a steep pitch to get the most solar gain. In the end the panel bridged both pitches because the installers couldn't put the tank any closer to our PV panels. Unlike grid connect PV, where the main concern is generating the most power irrespective of time of year, solar hot water is all about getting the most heat out of the sun on the most days (since you can't store or feed the power elsewhere). This then minimises the amount you need to boost the hot water and maximises the efficiency of your system. In fact, if I were to build my own house I would consider having a roof at 25 degrees pitch for PV and a separate roof at 45 degrees for solar hot water.

Choosing solar was just the beginning. Would we go for a roof mounted tank or not, 180L or 320L, glycol panels or water, gas or electric boosting, stainless steel or ceramic tank, etc.

Roof mounting is a no brainer for me. Why would you want to defy gravity and use power to pump water from a tank on the ground to panels on the roof when you can use gravity to do all the work for you by mounting a tank on your roof? Roof mounted tanks (also known as thermosiphon systems) use less power and are more reliable (no pumps, etc to break down) so that's what we have. As the water in the panels heats up it rises into the tank, as the water in the tank cools it falls to the bottom and back into the panels.

We don't use much water, so my feeling was that 180L would be plenty and it turns out it is. I didn't appreciate it at the time we purchased, but having a 320L tank doesn't mean you have more hot water. It means you have more water at the same temperature as a 180L system, which isn't much help if you need to boost in winter (in fact you'll end up paying more for boosting a larger tank). This is because a 180L tank is installed with 1 solar panel and a 320L tank is installed with 2 solar panels, because it suits the tank size. Having 2 panels and a small tank would mean overkill for 9  months of the year and having 1 panel with a large tank would mean tepid water for 9 months of the year. So getting a larger tank means you have more water, not hotter water. As long as 180L is enough hot water, there is no point getting a larger system. Since we use 200-300L water a day in the house, this probably equates to about 100-150L at most of hot water and much less in summer (the hotter the water the more cold water it is mixed with to make it safe and usable).

The solar collectors are either filled with glycol or water. I don't understand this in too much detail, but we opted for glycol since they are more efficient and when they get to a certain temperature they shut off, whereas with water they can't shut off and the tank may need to purge (let off hot water) in summer, which is a waste of water. I had a look at evacuated tube technology, but my feeling is that it's mainly designed for cooler climates and that it wouldn't be worth the extra money in Perth.

The boosting system is an interesting one. Many people are advised to get IG as the boosting system for SHW (in fact you can't access some government rebates unless you gas boost), since gas is a more efficient way to boost than electricity. Modern IG systems are very efficient these days, partly because they don't have a pilot light burning 24/7, they have an electronic ignition which only lights up when you need it. Electric boosting works just like a kettle, there's an element in the tank which heats the water. We opted for electric boosting, partly due to cost ($1,500 less) and partly because I wanted to be in control of the boosting. I want to know when we've run out of solar hot water because then I can change my behaviour to suit the conditions. For instance I can skip a shower or wash the clothes on cold. With gas boosting you never know when you're on solar or gas because it just cuts in when the tank water reaches a certain temperature. This means you have no feedback loop from the hot water system and you can't change behaviour accordingly. This is a big deal for me, since cutting my emissions is the main reason I'm doing this. Also, I've worked out it costs me about $20 a year to boost. Let's say gas cost half this ($10) and IG systems last 15 years. This means IG saves me $150 over that time, but costs me $1,500 (a $1,350 loss). Doesn't seem too economical to me! The fact that I am sometimes inconvenienced because I have to wait 30 minutes for the booster to heat my water is not that big a deal.

Lastly we had to choose between stainless steel tanks and ceramic lined tanks. Ceramic lined tanks have a sacrificial anode in them which corrodes over time to protect the tank from impurities in the water. You need to replace these every 5 years and then the tank should last 25-30 years. Stainless steel tanks don't have an anode since they are supposedly rust proof. In reality even stainless steel has imperfections and sometimes can rust, in which case you need to replace the whole tank. We went for the ceramic type for peace of mind. I know I won't forget to get the anode checked and I just think the tank will last longer. The company we used are Solarhart, which is an Australian owned and manufactured product.

Here is a our weekly gas usage with and without solar.We use gas for heating, cooking and hot water. We use most in winter, mainly due to heating but also because water in the hot water tank cools more rapidly in winter.We cut our usage from 11.3 kWh a day to 3.7 kWh a day (by the way, if you're in WA and want to convert the units on your meter to kWh, multiply them by 11.3 (don't ask me why!)). This means that heating water used approximately two thirds of our gas (assuming our gas use for heating and cooking were similar in both years). We've had a solar oven for the last year but I don't think that would have reduced our gas use that much. If you're wondering about the weeks in summer in year 2 being as high as year 1, those were preserving weeks when we were using the gas hob for big batches of tomatoes and other fruit.

Converting to kWh is good because you can then calculate your combined gas and electricity use in the same units. I was interested to see this since our boosting with electricity would have bumped up our usage a bit. I estimate that we used roughly an extra 0.5 kWh of electricity a day for 22 weeks between May and September to  boost our hot water. Overall, we cut our power usage almost in half by getting SHW, from 15.6 to 8.2 kWh a day (see running average chart below). This is roughly half the consumption of low users stated by Living Smart for a family of 3 people in Perth, which means we use about a quarter of the 'average' family's consumption.

What about the economics? Our system cost us $3,500 after rebates. We made a saving of $290 on our bills in the first year, which comes to $270 after deducting boosting costs. Assuming gas price rises of 5% a year this means a payback time of 10 years for us. This means we should get 14-19 plus years of free hot water and savings of around $17,000 over 30 years ($13,500 after initial costs). Most people would pay off much more quickly though, with some high users paying off their costs in 3-4 years. Our combined electricity and gas bills should be between $0 and $50 for the next 9 years (this will increase when the electicity Feed in Tariff expires). I feel the $10,000 we invested in PV and SHW was money well spent, since we'll have very low bills for the next 25 years at least. In uncertain economic times this is a good thing. If the GFC Mark II comes sooner rather than later, I could lose my job but at least I  wouldn't have to worry about huge utility bills.

How far behind peak oil is peak gas? I'm not sure but I'm pretty confident it's a fair way until peak sun...