Here is a very rough solar power survey for my house. Based in large part on the excellent design guide [1] book from Wind and Sun Ltd.
The best facing roof area is 65° off south (255° in fact). We also have a dormer window in the way, so at best, an area of 6m x 2m is available. Considerably less when accounting for access. The roof is at a 40° angle.
The irradiation correction factor for this tilt and azimuth angle gives a correction factor of 89% of full power output. The site is not shaded.
The UK solar radiation map gives around approx 890 kWh annual energy production for a 1kWp solar PV module in Southampton.
There is space for the SR-6 module from Wind and Sun Ltd., which is 4.8m x 1.6m. With a rating of 800Wp from 9m2 of panels. The price of this is given as £5K to £6k per kWp. Let’s assume £5K. As this is a grid connected system (see diagram), a DC isolator for £60, two AC isolators for £35 each plus one of the Sunny Boy 1100W String Inverter at about £1000 (£800 here) are needed. A new consumer unit is probably also required at ~£500.
An OfGem approved second hand feed in meter can be acquired here for £25.
Total spent so far (not including installation + mounting kit + connection fees ) = £6455.
Estimate of energy harvested per annum is (89% correction factor) of (890Wh insolation) times 800Whp = 633kWh per annum.
Current feed in tarrifs (FIT) for retro-fit are 41.3p per kWh. But that will reduce depending on when you fit the panels. So my 633kWh per annum equates to about £260 per annum in FITs. I also save about 17p per kWh from having to buy from the grid, another £107 saving. That is rather a long payback, even without going into the discounted cashflow analysis. Roughly 17 years.
Our annual consumption is about 4300kWh. Obviously we couldn’t supply all of that ourselves without a battery bank. Time for another estimation…
Some more related links:
Sitemap of Department for Energy and Climate Change.
The Govt standard assessment procedure for Solar PV, page 70, Appendix M.