Going Solar: Malcolm

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.

Malcolm's house from the South-East
Mature trees: The house from the South-east, with Poincianas on the footpath in front of an even taller Poplar Gum just inside our fence and an under-storey of Frangipanis (leafless in winter). The Macadamia and Paperbark (the tallest tree on the left of the picture) on our southern fence and the Mango in the the back corner of the block are not so visible but should not be forgotten.

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.)

16 thoughts on “Going Solar: Malcolm”

  1. Results for the month of September are as follows:
    Total output: 213 KWH or 7.1 KWH / day.
    Total exported to grid: 116 KWH or 3.9 KWH / day.
    Both these figures are higher than the equivalents at the end of August, as expected: days are longer, the sun has moved more directly overhead and skies are still mostly clear.
    Net benefit = (97 KWH used here, replacing grid supply at 22.6 c/KWH) + (116 KWH exported at 44c/KWH) = $73 or $2.45 per day, without any special action to shift daytime usage into evenings to maximise power export.

  2. On the same basis, results for the month of October are as follows:
    Total output: 210 KWH or 6.8 KWH / day.
    Total exported to grid: 155 KWH or 5.0 KWH / day.
    The total output is almost the same as for September but we exported more of it (less daytime power usage at home, for some reason).
    Net benefit = $81 or $2.60 per day.

    Our electricity bill for 1/8/11 – 28/10/11 arrived just after I prepared the monthly figures.
    Our four previous accounts were all in the $400-$425 region. This one was $175.
    Contributing factors: $50 from switching the pool pump to the off-peak tariff, before the beginning of the quarter; $112 from solar power we exported to the grid; and about $60 of our own solar power used instead of power from the grid during the day.
    Note that we have still saved nothing from putting our solar hot water service booster on the off-peak tariff because we have still not used the booster.

  3. On the same basis, results for the month of November are as follows:
    Total output: 246 KWH or 8.2 KWH / day.
    Total exported to grid: 117 KWH or 3.9 KWH / day.
    The total output is up on September-October but daytime power usage at home is back up so exports are lower than October and similar to September.
    Net benefit = $81 or $2.70 per day, almost the same as last month.

  4. On the same basis, results for December are as follows:
    Total output: 213 KWH or 6.9 KWH / day.
    Total exported to grid: 92 KWH or 3.0 KWH / day.
    The total output is back down to September-October levels (longer sunlight hours more than counterbalanced by days of cloud) and daytime power usage at home is up too (mainly aircon) so exports are lower than Sept – Nov.
    Net benefit = $68 or $2.20 per day.

  5. On the same basis, results for January are:
    Total output: 213 KWH or 6.9 KWH / day – exactly the same as December.
    Total exported to grid: 86 KWH or 2.8 KWH / day – down a bit, presumably because of more aircon use.
    Net benefit = $66.50 or $2.15 per day.

  6. The results for February are very similar – not surprisingly, since the weather has remained unsettled but not constantly overcast.
    Total output: 185 KWH or 6.4 KWH / day – down a little on Dec-Jan.
    Total exported to grid: 87 KWH or 3.0 KWH / day – up a little on Jan.
    Net benefit = $6o.40 or $2.08 per day – down a little in line with total generation.

  7. March turned out to be our lowest-producing month so far:
    Total output: 161 KWH or 5.2 KWH / day – previous lowest was 6.4KWH/day
    Total exported to grid: 76 KWH or 2.5 KWH / day.
    Net benefit = $52.65 or $1.70 per day.
    This is the seasonal low which we expected, of course, some time in the Wet. Signs at the moment are that the Wet finished last Monday, 20.3.12, so April’s figures should be higher.
    Incidentally, the relevant authority recommended last week that domestic electricity tariffs should rise. Our shiny-new Premier is caught between that recommendation and his pre-election promise to keep the cost of living down … I wonder which way he will jump.

  8. April was only a little better than March:
    Total output: 169 KWH or 5.6 KWH / day
    Total exported to grid: 80 KWH or 2.7 KWH / day.
    Net benefit = $55.31 or $1.84 per day.
    We did pass the 2 MWh total generation milestone during the month. That second MWh took us almost exactly six months (mid-Oct – mid-April) to produce, but it was the six months which included the whole of our Wet season.

  9. May is our lowest yet, but it may well be the lowest of the year considering that we are now only three weeks from the shortest day of the year and have had a couple of exceptionally wet, cloudy weeks – the coldest May day in 22 years was last week, and the BoM recorded two days with zero hours of sunshine.
    Total output: 141 KWH or 4.6 KWH / day*
    Total exported to grid: 52 KWH or 1.7 KWH / day.
    Net benefit = $43.10 or $1.39 per day.
    * The running average for the last nine months is still 6.4 kWh / day, slightly above expectations.

  10. The beginning of the month was record-breakingly wet but we have had clear skies for the latter part of the month and days are getting longer. We have turned the corner, at last, in terms of output.
    Total output: 145 KWH or 4.7 KWH / day
    Total exported to grid: 33 KWH or 1.1 KWH / day (not quite sure why that dropped off; perhaps more use of the bore pump to water the garden, plus a bit extra in the house).
    Net benefit = $37.70 or $1.21 per day, fractionally below our previous low.

  11. Total output for August: 191 KWH or 6.2 KWH / day, well up on July.
    Total exported to grid: 66 KWH or 2.1 KWH / day.
    Net benefit = $57.90 or $1.87 per day.
    This completes a year of updates and I will pull all the results together in a new blog post sometime soon.

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