Solar Generation Estimate / ROI

How much would/should it generate/return on investment etc?

A good site to use to get an idea of likely generation is to go to
Photovoltaic Geographical Information System - Interactive Maps
at http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php

Solar radiation database used: PVGIS-CMSAF Nominal power of the PV system: 3.8 kW (crystalline silicon) Estimated losses due to temperature and low irradiance: 11.7% (using local ambient temperature) Estimated loss due to angular reflectance effects: 3.4% Other losses (cables, inverter etc.): 5.0% Combined PV system losses: 19.0%

Fixed system: inclination=40°, orientation=-65° Month Ed Em Hd Hm Jan 2.79 86.4 0.86 26.6 Feb 4.91 137 1.50 42.1 Mar 8.78 272 2.73 84.6 Apr 12.30 368 3.94 118 May 14.10 436 4.58 142 Jun 14.40 432 4.76 143 Jul 13.70 426 4.57 142 Aug 11.70 363 3.87 120 Sep 9.32 280 3.01 90.3 Oct 5.75 178 1.81 56.2 Nov 3.47 104 1.07 32.1 Dec 2.42 74.9 0.75 23.2 Yearly average 8.65 263 2.79 85.0 Total for year 3160 1020 Ed: Average daily electricity production from the given system (kWh) Em: Average monthly electricity production from the given system (kWh) Hd: Average daily sum of global irradiation per square meter received by the modules of the given system (kWh/m2) Hm: Average sum of global irradiation per square meter received by the modules of the given system (kWh/m2) According to  http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php So in theory our ESE facing roof should generate 3160 kilowatt hours of electricity per annum.    We're signing up to the Feed in Tarriff where we get paid to generate PV electricity which  means we will be paid 14.9p for every kilowatt hour we produce (called the FIT rate) and an additional 4.9p for half of the power we produce (called the FIT export rate)  - the assumption being that we will use half the electricty we generate). So in the first year we should get 3160 x 14.9p + 1580 x 4.9p meaning a cheque of about £548. We will also be expected to use about half of the electricity which is seen as a benefit of about £189 so the saving in year one is about £733 So that's on the bad side £730 odd quid in year one.  However, the important thing to note about FIT is that it's not metered going back into the grid if your system is 4K or less, SO you can use 100% of the power you use!  Which means if we're clever and switch on stuff when the sun doth shine we will do even better. Another reason I've done it is that it's ecologically good, and it gives me a better understanding of climate and seasons just as doing the allotment does.