Going solar – when should I jump, and how many panels?

Pondering adding to the solar hot water on my roof with PV panels for electricity generation.

My last electricity bill says I used up 659 kWh in 92 days, costing $187.61 (only including the cost for power and the 100% GreenPower surcharge; excluding the $76.41 service charge which I’d incur no matter how much power used)… that adds up to 2614 kWh in a year costing $744.32, or about 28.5 cents per kWh.

According to Origin Energy’s online quote (which I’m using as a rough measure, because I use them at the moment and they have a 2-years interest-free deal — obviously other companies may have better offers):

  • a 1.5 kW system costing $2315 will generate about 1971 kWh in a year
  • a 2.07 kW system costing $4315 (which includes a $250 discount because I got the solar hot water through them) will generate 2628 kWh in a year
  • a 2.76 kW system costing $5815 (ditto on the $250 discount) will generate 3626 kWh in a year

Leaving aside feed-in tariffs, and assuming for a moment that every kWh generated I actually use (which wouldn’t be the case), theoretically the 1.5 system would save me $562 per year, taking about 4 years to pay off.

The 2.07 system would pretty much save me the full cost of power every year, but take almost 6 years to pay off.

The 2.76 system would give me an excess of about 1000 kWh of power each year. The feed-in tariff is only 8 cents per kWh these days, so I’d be saving $744 plus another $80 or so, so it’d take about 7 years to pay off.

Some factors to consider:

If I cave and get some kind of cooling system, then my energy consumption will of course go up.

From what I understand, PV panels are dropping in price pretty fast. The longer I wait, the cheaper they’ll be (which is why I’m a little cynical about the ads you see on the telly implying if you don’t get in and order quickly, you’ll end up paying more).

Meanwhile, electricity prices are expected to rise only moderately in the next few years.

The bigger the system, once paid off, the greater potential in future years to make more money back from the feed-in tariff.

But I also need to check how much space I actually have left on the north and northwest-facing sides of my roof, given the solar water panel already up there.

And of course, once I jump in and switch to solar, I’ll be markedly reducing my personal emissions, which will be good!