Solar & battery
Solar Panel Calculator
How many solar panels a home needs, and what they produce together.
Result
System derate covers inverter losses, wiring, heat, soiling and panel mismatch. Around 0.80 is the figure most design tools use; a hot climate, a dusty site or a shaded roof pushes it lower. It is why a system never produces the sum of its panel ratings. Installed cost per watt varies widely by market, roof complexity and whether the roof needs work first. It is a planning figure, not a quote.
Get a Free Business AuditQuestions
About this calculator
How many panels for an average home?
Typically 15 to 25 at current panel ratings, but usage varies by a factor of three between similar houses. Your own kWh figure is the only one worth using.
Do panels degrade?
Yes, usually around 0.5% a year, with most warranties guaranteeing roughly 85% output at 25 years. Long-term savings estimates should account for it.
The formula
panels = daily kWh needed / (panel kW x peak sun hours x derate)
Put this calculator on your site
Free to embed. Paste this where you want it to appear. It stays up to date automatically because it loads from BDEVY.
Please keep the attribution line. It is the only thing we ask in return.
Keep going
Related calculators
Solar System Size Calculator
System size in kilowatts to cover a given share of a power bill, from usage and local sun..
Open calculatorSolar Panel Output Calculator
What one panel actually produces per day and per year, against its nameplate rating..
Open calculatorSolar Panel Quantity Calculator
Panels to order for a system, with spares for breakage in transit and handling..
Open calculatorEstimating is the easy part
The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.