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Help - Select your own roof

You can refine your comparison results for your own roof. This has the advantage that only systems that would fit your roof are shown in the results. Also, the calculations of system output (in kWh) and financial return are based on your real solar potential. You can select your own roof as follows:

  1. Find your house:
    Enter your postcode or address to help you find your own house.
  2. Select your roof:
    Click in the map on all corners to select this part of your roof,
    preferably without obstructions and South-facing.
  3. Highlight your gutter:
    Click inside the selected area until you highlight the lowest side
    of your roof (select any side for flat roofs).
  4. Use dropdowns:
    Use the dropdown boxes on the right to estimate roof angle,
    level of shading and your energy usage.

Based on your roof selection we calculate your solar potential (% of optimal) and available roof area (in square meters). Solar potential is impacted by roof orientation (south is best), roof angle (30-40 degrees is best) and roof shading (none is best). You will return to the comparison table (get help with the comparison table) but you will see the solar potential slider is fixed on the percentage for your own roof. Also, any results shown would have a system size (in square meters) that fits on your roof selection.

Select your own roof – Top Five Tips

  1. Zoom in on your roof as much as you can
  2. Click clockwise on the four corners of your roof
  3. Highlight the lowest side in red (the gutter)
  4. Dropdowns have info bubbles that provide context
  5. Remember your potential so you can adjust slider on next visit

Select your own roof – Roof Variables

When you select your own roof you have to set a number of variables. Explanation of these is shown below:

Roof Variable Explanation Tips about Usage
Roof size Click inside the map to select all corners of one part of your roof (not obstructed and preferably South-facing)
  • For a 4 kWp system you’ll need about 30m2
  • Roofs selections are best rectangular, as sharp corners limit the usable space 
Orientation Click inside the selected area on the map until you highlight the lowest side of your roof (select any side for flat roofs).
  • The orientation is calculated as being perpendicular to the red line
  • Align red line with the gutter
Angle of roof (degrees) Select the picture with the angle that best matches your roof (an angle around 30-40 degrees is optimal)
  • Angle is less important than orientation and shading
  • Even flat roofs have a solar potential as high as 90%
Roof shading Select the level of shading during daytime. Please be aware that even small levels of shading from e.g. chimneys or trees can severely reduce solar system outputs.
  • Shading impacts your potential the most due to panels being connected in series rather in parallel
  • This means the weakest link (one shaded panel) brings down outputs for all panels
Yearly electricity usage (kWh) Select the number of bedrooms in your household or manually enter the expected yearly use in kWh
  • In the optimal situation all electricity generated is used in your own house, as the export tariff is rather low
Do you own or rent this house? Solar panels cannot be installed on your roof if you rent this house.
  • Solar panels cannot be installed on your roof if you rent this house unless you have permission from the owner of the property


Select your own roof – Solar Potential 

Based on your roof details we calculate your solar potential which can either be excellent, good, very good, medium or poor. The solar potential impacts the system output, year one return, payback time and profit after 25 years. Any solar potential above 90% is very good or excellent, while a solar potential of 80-90% is still viable from a financial perspective. The explanation of impact of your roof variables on your solar potential can be found in the solar education. After you have calculated the solar potential for your own roof it is no longer possible to adjust this slider, and all systems shown fit on your roof.