Going Solar: David

There has been a lot of talk about domestic solar power systems in the last year or so but most of it seems to be coming from governments, suppliers and others who may have vested interests, so it’s understandable that we listen to it with a degree of scepticism.

I thought a real-life example or two may help to sort out the truth from the hype.   Sometime soon I’ll post my own story, of the installation on our own older high-set house in Mundingburra. Meanwhile, here are the experiences of David and Kate, a young professional couple living in a small modern house in the new suburb of Douglas. In David’s words (and with my thanks to him for allowing me to quote him):

Our 1.52 kW solar power system was installed by a specialist PV company in March 2011 and the entire process has been extremely smooth. The installation was performed amazingly quickly, with about six staff working together to place the panels on the roof, provide conduit from the panels to the solar inverter through our roof, and rewire our switchboard. The whole process took only a few hours to have everything in place and signed off.

After the installation, on an average sunny day, we would see generation of at least 7 kWh, even reaching 8.5 kWh on our best day. Through this, we were seeing our power usage at home more than negated, with our meter steadily going backwards. That said, we’re not a typical situation since we only have two of us at in the house, we work 9 to 5 on weekdays, have a two-storey, north-facing house with a perfectly angled roof and no trees nearby, and are extremely power efficient around the home with LED halogen-replacement lights and gas appliances in use.

After the installation, we applied to Ergon Energy for a new electricity meter so we could get the bonus feed-in tariff. Unfortunately, this process took nearly two months of waiting – but given the recent cyclone and number of people purchasing solar panel systems, that was understandable. In late May 2011, our new meter was installed and we’ve been able to watch how much we’re saving off our power bill. Because we use so little power during typical days, most of our generated power goes into the grid at 44 cents / kWh, and we’re therefore making a fair amount of money.

As a rough indication, our new meter has been in place for just over a month, we’ve pushed around 140 kWh into the grid at 44 c/kWh and we’ve only used 108 kWh at 22 c/kWh, giving us a credit of about $38 so far. This works out at around $2 per day in credit, after paying for power usage. So, since our previous year’s power bills were approximately $700, we should be looking at a net benefit of over $1200 per year (and that’s taking into account air conditioning during summer days). Our system cost was $3300, so it’ll pay for itself in no time, not to mention the value it has added to the house.

We’ve changed our lifestyle a little with the solar as we try to do washing, dishwashing and similar powered activities when the sun isn’t shining – either early in the morning or in the evening – to avoid using our solar power and losing out on the bonus. Aside from that, we just keep being electricity conscious and turning off everything we can when it’s not in use.

We’re still waiting to receive our first power bill after the new meter was installed but our previous bill (i.e. after the panels were installed but before we started getting the feed-in bonus) saw our power bill halved just by having the solar panels installed for a third of the billing period.

Kate and I are very thorough with planning so we made sure we knew what we were getting, and we made sure to have the panels in the right place, etc, etc. Aside from the slow Ergon hook-up, we’ve had no problems at all. Anything we didn’t expect? We didn’t really expect we would be saving so much!

6 thoughts on “Going Solar: David”

  1. David sent me an update this morning:
    “Total generation: 693.5 kWh
    Time operational: 1167 hrs
    Days installed: 114 days
    Average generation per day: 6.1 kWh
    Most recently we’re getting around 7.x kWh (yesterday was 7.4 kWh, and 7.3 before that) on days of full sun and considerably less if it’s overcast – down to 3 kWh or so.”

    He mentioned seasonal change in system output and I did some quick calculations. We are going to have three factors to consider – day length, temperature and cloud cover:
    • Day length here varies from about 11 hours in midwinter (three weeks ago) to 13 in midsummer, and that should translate pretty directly into an increase of 15% or so. There will also be a slight additional increase from the sun moving more to the north in summer, so let’s guess a 20% improvement from midwinter to midsummer.
    • Panel temperature is going to be higher, and that reduces panel efficiency slightly but I don’t know the size of the effect – perhaps somewhere 5 and 10%.
    • Cloud cover will be higher in the Wet and the effect is again hard to predict – perhaps 10 to 15% on a monthly basis, though with a greater range on a daily basis.
    It all should balance out pretty well, I think, so my guess is that his longterm average will stay between 5.5 and 6.5 kWh / day. However, the best months will be those with longer days but still mostly clear skies and less-than-maximum temperatures, so September – October could be better than either midwinter or midsummer.

  2. Another update from David:
    I’ll keep on keeping tabs on our generation as time goes by, both long term and short term and keep you posted if there’s anything interesting.
    Recently we’ve seen days of 7.9 kWh, we’re approaching 1 MWh of generation in total, and our first post-solar power bill is due to arrive any day.
    As for what you’ve mentioned about the conditions, you’re absolutely right on all accounts. With regard to temp increases on the panels, the guys who were installing our panels mentioned that every 1 degree increase in temp could equate to 0.5% decrease in efficiency. I’m not sure how scientific that is, nor how hot the panels get up on the roof, but it could be something like that.

  3. And another update since we’ve just received our first power bill notice since installing solar. The results are in and here they are:

    During the last 77 days (time since the new meter was installed), we sent 387 kWh back into the grid, giving us a credit of $170.28 (44c / kWh). During the billing period (past 93 days), we used a mere 270 kWh, and that, with the service fee, was a cost of $85.24. The QLD ambulance levy has been abolished as of the start of this financial year (hurray) so when pro-rata costs are deducted, our grand total is a credit of $74.75. Outstanding when you think in just 77 days, we more than twice paid for the power we did use at night time.

    The next notice will be interesting, because it’ll entirely cover time with our new meter and without the ambulance levy. Looking further, it’ll be even more interesting to see how things fare in the summer with air conditioning. Finally, long term, I’m under the impression if the account’s in credit for 12 months we can request a cheque. Will see how that pans out!

  4. Latest news from David:
    Lately our daily production is usually at least 7.5 kWh depending on the weather. We had our very best day in the middle of September – being 9.07 kWh for the day, and we have had a few other days close to that.
    I should note these were pretty much immediately after I got up on the roof and washed the panels down, not exactly an easy job with our house given the height.  Amazing to see just how much dirt/ash was up there – presumably from the fires not too long ago.  

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