SOLAR DESIGN
A solar generation estimate is a model, not a guarantee. Its usefulness depends on whether the model reflects the actual site.
The main site variables
MCS performance-estimation guidance uses the array rating together with location, pitch, orientation and shading. Those variables explain why two systems with the same installed kWp can have different annual outputs.
Why shading needs care
Chimneys, trees, neighbouring buildings and roof geometry can reduce production at different times of day and year. Remote imagery can help at an early stage, but the design should be updated if a site survey reveals conditions that were not visible remotely.
What a useful proposal should show
Look for the installed kWp, the annual generation estimate, the assumptions behind that estimate and any shading or layout constraints that materially affect it. Additional software estimates can be useful, but they should not be presented as guaranteed output.
Related: Solar PV design & installation · Home solar
Source: MCS MIS 3002 performance-estimation methodology. Current MCS documents are available from mcscertified.com.
FROM GUIDE TO PROJECT
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