Solar panel payback calculator

We are currently working on a printed version with full explanation notes that you can examine at your leasure. Feel free to check back here, it should be coded and fully operational within the next couple of weeks.

If you adjust any of the numbers within the white input boxes ( eg:Electricity cost per unit(p/unit) ), click the mouse outside the box to update the financial figures .

Your System Information

Please select your region

N & C Scotland
S Scotland - N England
Midlands - N London
S England
SW England

My roof is facing

South SouthEast SouthWest East West

Anticipated date of installation

before Dec 12th 2011 Dec 13th 2011 - Apr 2012 Apr 2012 with EPC Apr 2012 without EPC

System size

1kWp 2kWp 3kWp 4kWp

Total system cost(£)

House occupancy during the day(%)

Please note : This calculator does not constitute financial advice. It is simply our attempt to inform based on all the information available to us at this time. Whilst we have considered most of the significant factors which affect the returns, we strongly recommend that you take up the option of a free survey to ensure that your personal circumstances and factors are consistent with these forecast returns.

A full print out version of the submitted information and returns along with a comprehensive explanation of the factors should be available here within the couple of weeks. In the meantime, we hope the pointers below help with your understanding of the calculations.

• House occupancy during the day(%)

  Used to estimate the amount of generated power used and therefore the amount exported back to the grid

• Electricity cost increase pa(%)

  The anticipated annual electricity cost increase. We've estimated a figure of 6% which is fairly consistent with global economic forecasts but you may wish to reduce this increase if you wish to be more prudent. Decreasing this % will reduce the anticipated return value from the solar panels since the value of the electricity you generate will be less.

• Retail price index RPI(%)

  The tariff payments will increase in accordance with the retail price increase. We've used the very conservative figure of 3%. Currently running at around 5%, the RPI is a measure of inflation. In general terms, whenever you here the phrase 'quantitative easing', expect inflation and therefore the RPI to increase, and the relative returns on savings to decrease.

• Interest earned on savings

  We've assumed that you can a 3.5% return on savings. That would be what you would get with your cash if you did not invest in solar generation. It is also assumed that the returns from the solar investment can be invested and receive the same rate.