PV Quick Quote

Solar PV Quick Quote - Assumptions


Cambridge Solar's 'Quick Quotes' are designed to be a quick and easy way for you to receive a personalised and reasonably accurate estimate for installing a solar PV system on your property. It also gives estimates for savings, income from the feed-in tariff, CO2 saved and investment payback times according to two sets of assumptions.

In order to arrive at these estimates we enter information about your property, the cost of a solar PV system and a few assumptions such as the price you are currently paying for electricity. This web page will go through these details so that you know exactly what the 'Quick Quote' is based on.

Site information

Based on what you tell us and maybe a Google Earth survey or some photos we enter details about the following:


This is which direction your roof is facing. South is ideal, North is best avoided, East and West can be fine. A compass or Google Earth is best for estimating this.


This is the angle of the pitch of the roof from the horizontal. Most roofs in the UK are around 35 degrees which is ideal for maximising the solar yield over the year. This can be measured by using an angle measurer on the rafters or estimated by looking at the gable end.

Shading issues

We need to know about the extent of any shading issues. Your descriptions, plans and photographs are all useful here. It is best to have as little shading as possible.

Available Area

This lets us know the maximum sized system we can fit on your roof.

Feed-in Tariff

The feed-in tariff rewards systems according to type and size. Retrofit get more than new build and larger systems get less than smaller systems. We specify the correct rate for your installation based on the FIT rates published by the Government. This can be found here (http://www.decc.gov.uk/en/content/cms/consultations/elec_financial/elec_financial.aspx). More details can also be found on our feed-in tariff page.

System Information

We carry out a basic design a for a suitable system for your property and supply some information on the components used and prices.

System Output 

For our quotes all installers are required to use the Governments Standard Assessment Procedure, SAP to work out output. However SAP uses weather data for the North of England. There are some more accurate online calculators available, the best of which is probably PV-GIS

Financial Model Assumptions

We use two assumption models for future benefits from your system. Our first, and preferred model is based on the Energy Savings Trust Cashback Calculator (found here). We have called this model the Energy Saving Trust Model. However some installers are using a model which we believe can be misleading. We have included the Industry Standard Model which use the same assumptions as the UK's leading solar PV installer. Both are explained in more detail below:

Energy Saving Trust Model

This model makes the following assumptions:

0% Fuel price increases over time

0% Inflation

0% Improvements in energy usage patters

Industry Standard Model

This model makes the following assumptions as standard. The actual figures can be found on your Quick Quote.

6% Fuel price increase over time

3% Inflation

10% Improvements in energy usage patterns

Shared Assumptions

These assumptions are shared between the two models:

Average electricity use for a domestic property in the UK is 3,080 kWh per year (Energy Saving Trust)

Average electricity price electricity is 12.95 pence per kWh (Energy Saving Trust)

Amount of electricity exported to the grid is 50%.

Final Notes

If you would like us to change any of the assumptions for your Quick Quote we are more than happy to do so.

Cambridge Solar is not a financial services company. Customers wanting to compare solar PV as an investment or security should consult an appropriate professional.

The figures we use in the financial models are in no way binding but meant to offer our customers an idea of the potential financial benefits of investing in solar PV.

Cambridge Solar's Quick Quotes are non-binding estimates. Cambridge Solar require carrying out a site survey and system design before issuing a full proposal with a formal offer.