Solar Calculator

Solar Calculator

This tool can be used to get a rough estimate for the amount of energy you could produce from a photovoltaic roof in your location, and the amount of income and savings this roof could generate.
You should never install a renewable energy generator without first consulting an expert! Please click here to learn more about the purpose of this tool and its limitations.


  • Step 1: Use the slider bars to select the size of your roof
  • Step 2: Click on your location on the map - a pin symbol should appear
  • Step 3: Use the slider bars to select slope and orientation of your roof
  • Step 4: Look at the Results section to see how much electricity and income your PV roof could generate
  • Step 1: Panel size

    Use the slider bar below to select the size/area/cost of your PV roof.

    Roof area [?] 18 m2
    Capacity [?] 2.5 kW(p)
    Cost [?] £pound;12,000

    Step 2: Location

    In the map below, different colours correspond to different amounts of solar radiation received in an average year.
    Click on your approximate location on the map below (map and radiation data from PVGIS © European Communities, 2001-2008).

    Step 3: Your roof - orientation and slope

    The amount of solar radiation received by your panels, and therefore the amount of energy produced, will also depend on the orientation and slope of the surface your panels are mounted on - typically your roof. Use the two slider bars below to select the approximate orientation and slope.


    Step 4: Results

    The table below show the amount of electricity produced and the income and savings generated during an average year.
    Note: The results below are approximate. Actual output will depend on many factors, including the weather. Also note that shading, e.g. from trees or houses, can have a very significant effect on results!

    Electricity produced per year
    Total electricity generated 0
    units used directly [?] 0 0
    units going out to the grid [?] 0 0

    Income generated per year
    FiT Generation Tariff [?] 0 0
    Export income [?] 0 0
    Electricity savings [?] 0 0
    Total annual income & savings 0

    Investment value
    Payback time [?] 0
    Profit over 20 years [?] (How long do PV panels last?) 0
    Rate of Return [?] 0

    Environmental Impact
    Energy required to produce your PV panels [?] 0
    Energy payback time [?] (learn more about energy payback) 0
    CO2 emissions avoided per year [?] 0
    reduction in one person's average total carbon footprint [?] 0

    More questions?

    The Centre for Alternative Technology operates a free and impartial Information Service which can help you to take the right decisions when it comes to renewable energy and sustainable living.

    Click here to contact us by email, or give us a call on 01654 705989.

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