Our first Feed-in tariff payment came in last month. The official figure shows 302.89kWh generated for the full quarter Sep/Oct/Nov.
Under the FIT system, we get paid 14.9p for every kWh we generate, which is £45.13 for this period. They assume we export half of what we generate back to the grid, and we get paid 4.64p per kWh for that half, which is an additional princely sum of £7.03, for a total of £52.16 paid into our bank account.
In addition to this, we benefit from the savings we make by using our own electricity and not having to buy it in from the grid. This is the most difficult benefit to work out. We have two electricity meters. First, the 'normal' one that everyone has, that counts up how much electricity we've bought from the grid. The second meter is installed with the panels and tells us how much electricity the panels have generated.
Consequently, there's no way of knowing exactly how much of our home-generated electricity we're actually using ourselves. Although I've worked out I can get an idea of how much we're using. It's a bit complicated, but here goes:
I look at our normal electricity meter at regular intervals during bright sunshine. If it is counting up, it means at that moment we are using all of the electricity we are generating, and still topping up with electricity we're buying from the grid. However, if it stops counting up, it means we are not buying electricity from the grid at that moment, and we are exporting our solar generated electricity to the grid. Therefore we are not using all of the electricity we are generating at that moment.
Over the sep/oct/nov quarter, I've been checking the meter reasonably regularly during bright sunshine, and every time, we have still been buying from the grid, so I'm feeling confident in assuming that every kWh we've generated we have also used ourselves. This may not necessarily be the case over the summer months when the array will be generating a lot more electricity.
We are currently paying 13.32p per kWh that we buy from the grid. So over the quarter, we have made 302.89kWh x 13.32p = £40.34 savings in electricity we've not bought from the grid.
This gives a total benefit to us of £52.16 + £40.34 = £92.50 for the quarter.
With the shortest day of the year smack bang in the middle, December is the lowest generating month for solar panels. My generation forecast based on the sunlight hours stats from the met office (http://www.metoffice.gov.uk/public/weather/climate/blackpool-blackpool#?tab=climateTables ) was 50.52kWh for the month (1.63kWh/day).
The actual total was a paltry 27.8kWh total for the month (0.9kWh/day) which is 55% of the forecast amount.
Whilst the autumn months' forecasts were pretty much on the money, December has been significantly down on the predicted amount. At the moment, my guess is that using the monthly 'bright sunshine' hours statistics from the met office is only part of the picture. I've noticed that over midday during mid winter, bright sun was generating only around 800-900W from our panels (their max output is 2000W), so the low winter sun really does hit the output wattage of the array quite hard.
The 45% drop in generation compared to the December forecast sounds like a lot, but it's only a 22.72kWh deficit for the whole month. In comparison, during just the last 4 days of August the array generated 27.8kWh.
Referring back to the conversations I had with the company that installed our panels, the chap there commented that every installation they'd done on the Fylde coast over the last couple of years had exceeded the forecast generation for the year. Which leads me to think (hope!) that over summer, the monthly generation will be higher than my forecast to bring the average up for the year as a whole.
Only time will tell.
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