As I said at the end of June, I think real-life examples may help to sort out the truth about domestic solar power from the hype. Here is the second of two recent Townsville installation stories. My own solar installation was not as straightforward as David’s but that may make it more useful for some readers.
We have lived in an older high-set weatherboard house (about 1950, a product of the post-war building boom) for nearly twenty years. When we decided to install a photo-voltaic (PV) system, we had to deal with a main switchboard as old as the house, mature trees surrounding and shading the house, and the need to work around our existing solar hot water system.
Every PV system installer who quoted for us told us that we would have to replace our switchboard. We were neither surprised nor particularly disappointed but it did encourage us to choose a company which has always done general electrical work and has recently added solar installations to its business, rather than a PV-only company, since we figured we could be sure the switchboard and solar system would be done together and work together. Since we were upgrading the switchboard anyway, we switched our solar HWS booster and the pool pump to tariff 33 (off-peak) to save ourselves quite a bit off our electricity bill quite apart from our solar savings (and yes, I know we probably should have done it years ago). The cost for all that work was $2000.
We opted for a 1.5 kW panel array, the usual entry-level configuration, but a 3 kW inverter so that we could add panels later without needing to upgrade anything else. The cost for the system was $3500 – not quite the cheapest quote, but all three were within a couple of hundred dollars of each other (and of David’s cost). The house faces East so our North-facing roof is relatively small to start with and (reasonably enough) our solar HWS panels and tank were right in the middle of it. The PV panels therefore had to face East or West, since South is the worst possible direction. East gets the most shade, so West it was. Installers’ estimates of the reduction in output as compared to a Northern aspect were in the 7 – 10% range, nothing we couldn’t live with.
Installation, in mid May, was not as smooth as we would have liked. The switchboard was no problem at all but the solar team were in the middle of the rush to get systems in before the federal government rebate dropped and made a couple of significant mistakes, installing the wrong inverter and installing the panels too low on the roof. To their credit, they fixed them willingly enough, but it took a while.
The percentage of generated power which we didn’t need should have been feeding into the grid and earning us money right from the day of installation, but Ergon also were swamped by the rush of people installing systems before the incentives dropped. An essential piece of paper went astray, and after it was found there was still a backlog of installation work, so that in the end there was a delay of exactly three months between installation and hook-up. It was irritating and disappointing but it doesn’t matter much in the long run: we can have lost no more than $100, which is negligible over even the first five years.
Our latest quarterly account (May – July) has been affected by far too many changes to give us a clear indication of the benefits of the PV system but we do know we have saved about $50 by putting the pool pump on the off-peak tariff. (We haven’t even used the HWS booster so there are no savings yet from that change – hot water can’t be any cheaper than free! – but we will get the benefit during the Wet season.)
Since the system was properly completed we have been getting a daily output of almost exactly 6 kWh. Taking seasonal factors (see my first comment to David’s story) into account, that happens to be roughly what we expect our long-term average to be. If it all went in to the grid at 44c / kWh it would earn us $2.60 per day; if we used all of it, it would save us $1.25 per day by replacing Tariff 11 power at 20.7c / kWh. Our net benefit is therefore somewhere around $2 per day, or $180 per quarter.
All in all, making the best guesses I can for the unknowns, pay-back time for the whole project (PV system and switchboard) looks like being in the 5 – 8 year range. That’s perfectly acceptable in itself and, like David, we are pleased with the value it has added to the house. Of course, if the electricity tariff rises (hands up everyone who thinks it is going to fall? No, my hand didn’t go up either), pay-back time will drop accordingly.
(A slightly different version of this post was published in Reef HQ Volunteers Association newsletter, Waves, for September 2011.)