Going Solar: Malcolm, one year on

We installed a 1.5kW solar power system on our roof in the middle of last year. As I said at the time, it took a little while to get it all connected and working the way it should. However, we now have a whole year of data on its performance, so we can assess the annual output and see the seasonal effects.

solar power output chart

The blue curve shows how much power the sytem has produced and, as expected, generally follows day length but with bumps created by specific weather conditions. The amount exported tracks it fairly well, but is reduced by air-con use during the hotter part of the year (the gap betweeen the two curves is widest from Dec-Feb). The spike in exports last September-October, incidentally, is explained by the fact that family members were away from home for several weeks: less consumed => more exported.

Annual numbers are:

  • Total produced = 2220 kWh (6.1 kWh/day)
  • Total exported to grid = 960 kWh, for $425 income
  • Total PV power used at home = 1260 kWh, for $270 savings
  • Total benefit = $700

In the coming year/s we can expect a slightly higher net benefit, since the electricity tariff has recently increased from 20.7 to 23.07 c/kWh. On the same output and consumption figures, the panels should save us an extra $20 per year because of that price rise. However, cutting our daytime power consumption would be even better. If we had used half as much power during the day this year, for instance, our net benefit would have been $130 higher. That is something we will now look at more carefully.

I will keep tracking monthly figures but won’t keep posting them to Green Path so my updates will be less frequent.

3 thoughts on “Going Solar: Malcolm, one year on”

  1. Our latest electricity account, for the three months ending 29.10.12, is consistent with these figures. Our total consumption was just under 1500 kWh and about 30% of its cost was offset by our export of 250 kWh back to the grid.
    The account was accompanied by a brochure encouraging us to shift our consumption to the economy off-peak tariff, which benefits Ergon because it reduces peak demand on their supply system. They currently offer $250 cash back for connecting the pool pump to the off-peak tariff (no good to us – we did it last year), $100 for doing the same with the hot water system (ditto) and $150 for replacing an old pool pump with a more efficient one.

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