If you’re thinking about rooftop solar, a little planning upfront can save a lot of money and confusion later. Most people get stuck on the same questions:
What system size (kW) do I actually need?
How many units (kWh/year) can I expect in the first year?
What savings and payback look realistic for my tariff and location?
(For installers) How do I do quick string sizing checks and a clean quote without spending hours?
So I built a practical Rooftop Solar Design Calculator (Excel Workbook). It’s designed USA-first, but it also works for India, Canada, UK/EU and other regions through region presets and editable assumptions.
What it helps you do (in minutes):
Size your system from annual usage
Estimate 1st-year generation (kWh/year)
Estimate bill savings + payback
Optional: module/inverter selection + basic string sizing + layout checks
Generate a shareable summary/quote page
How to start (2 minutes):
Select Region Preset
Enter annual kWh + tariff + solar resource (PSH)
Read Quick Results
I also wrote a step-by-step user guide on my blog: Solar PV System Design Calculator (Excel) for Homeowners and Small Installers
Get the workbook from my store: Rooftop Solar Design Calculator (Excel Workbook)
