I have been connected with two domestic solar power projects which I described here on Green Path at the time, and today I have news on both of them.
Hervey’s Range in winter
The first item concerns our solar bore pump on Hervey’s Range: we pulled down the disused power line over the weekend and took it to a scrap metal merchant. Pulling it down made the property tidier and safer and was a good excuse for mucking around in the bush for a few hours on a beautiful sunny day, while the $150 we got for it was a belated cash-back bonus on our purchase of the solar pump system.
The system itself, six months down the track from its installation, has performed well. Cloudy weather has not troubled it as much as we thought it might, and neither has the shorter span of daylight in winter.
Back in town, the 1.5 KW system we put on our roof has just passed a good round number in its total output: 7 000 kWh, or 7 MWh. We installed the system in May 2011 so it has produced an average of 6.2 kWh per day for three years. By power-station standards that’s nothing, of course, but it’s a useful percentage of a household’s consumption: Ergon says (on the back of our power bill) that the average daily consumption for a household like ours is about 20 kWh per day, so our panels are producing nearly a third as much as we use.
Of course, we use some of our solar power during the day and export the rest of it and then use Ergon’s power all night, so our net benefit doesn’t quite reflect those numbers. I did the sums a year after the installation and came up with a figure of $700 p.a., with the expectation that that would increase as power prices increased.
The general tariff has just gone up from 29.4 to 30.8 c/kWh, which doesn’t look like a big change until you note that the same tariff was only 19.4 c/kWh when we installed the system three years ago.
In May 2011 the “service fee” or “daily supply charge” was only $23 per quarter, whereas by May this year it had risen to 55 cents per day ($49 per quarter) and it has just increased to 92 c/day (about $83 per quarter). That will make it a major part of our power bill.
The huge increase in the supply charge is obviously Ergon’s attempt to make up for people like ourselves who still want the security of mains power but don’t actually use much of it because we generate a lot of our own. That’s fair enough, maybe, but it simultaneously encourages us (and people like us) to go completely off-grid. I will return to this scenario in another post; meanwhile, Australian households could go off-grid by 2018 is a thought-provoking introduction to it.