Assessment and installation
How accurate are online solar calculators?
An online solar calculator is only as useful as its inputs, methods and disclosed assumptions. A personalised result should be judged by what it models and what has been validated, not by how precise its headline number looks.
By VERA · Reviewed
Look beneath the headline
Check whether the tool uses a typical system size or a layout for the actual roof. Ask how it handles roof faces, shade, obstructions and usable area. Financial projections add further assumptions about costs, tariffs and household consumption.
Precision is not proof
A result shown to several decimal places can still rest on uncertain inputs. Repeating the same result shows consistency, not necessarily agreement with an installed system’s measured production. Useful validation compares an appropriate set of predictions against reliable observations.
Use the result as evidence
VERA explains its assessment approach and the limitations of remote data. It does not replace the installer’s final survey. When comparing tools, use the same property and proposed system, and look for transparent assumptions rather than treating every difference as proof that one tool is wrong.
Sources and further reading
This guide gives general information. Your assessment is an estimate; installation design, suitability and price need confirmation for your property.
Keep exploring
- How does VERA assess my roof's solar potential?
- How to get a free solar panel quote with VERA
- How to choose the best solar panels for your home