Solar Panel & Electric Bill Savings Estimator

How Solar Panel System Capacity Is Estimated

This calculator turns monthly grid consumption into a rough solar-system suggestion. Its current heuristic estimates capacity at roughly 1 kW for each 120 kWh of monthly use, rounding up to a whole kilowatt. For example, 500 kWh per month produces a suggestion of about 5 kW. This is a quick starting point, not a site-specific engineering design or a promise that solar will eliminate the bill.

Actual generation depends on location, season, average peak-sun hours, panel direction and tilt, shading, temperature, inverter losses, dust, and system availability. A proper estimate uses local solar-yield data and compares expected daily generation with when electricity is consumed. Review at least twelve months of bills if your usage changes seasonally, and ask an installer to inspect the roof, wiring, inverter rating, and utility interconnection requirements.

Understanding the battery-backup estimate

The number shown by this simple tool is derived from monthly units divided by 30, with a small minimum. It approximates average daily energy use, but it does not measure the appliances you want to keep running during an outage. Battery sizing should begin with the critical load: add the watts of those devices, multiply by the hours of backup required, and divide watt-hours by 1,000 to obtain usable kilowatt-hours.

Because batteries have a permitted depth of discharge and inverters lose some energy, nominal battery capacity generally needs to be larger than the energy delivered to appliances. For instance, a 500 W essential load running for four hours needs 2 kWh delivered before losses and reserve are considered. Starting motors, surge demand, battery chemistry, age, and cloudy-day recharge also matter. Treat this page as an initial comparison only, and have a qualified installer verify battery voltage, capacity, protection, and safe wiring.