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System size calculator

How big does your solar system need to be? Enter your annual electricity use and target offset; the estimator returns a kW range, panel count and estimated production. It is a planning tool, not a roof design — shading, orientation and tilt are refined in a site survey.

Solar installer measuring a roof plane with a laser tool before designing a solar system.
A site survey measures roof planes, pitch and shading — the real way system size is finalized.

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Finding your annual kWh

Your bill shows monthly kWh — multiply by 12. If you only know the monthly dollar amount, divide it by your rate to estimate kWh. The US average is ≈10,100 kWh/yr (≈843 kWh/mo, EIA 2026). If you plan an EV, heat pump or induction range, model the future load, not just today’s — an undersized system is expensive to expand later.