Solar System Size Calculator

Calculate the kWp you need based on your monthly electricity bill

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Your average monthly electricity cost

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Average cost per kilowatt-hour (US avg: $0.12 – $0.16)

US avg: 4–6 hrs | Tropical: 5–7 hrs | Check NREL solar maps for your area

Includes inverter, wiring, dust, temperature losses (typical: 15–25%)

Frequently Asked Questions

How do I calculate the solar system size from my monthly electricity bill?
Divide your monthly electricity bill amount by your electricity rate per kWh to get your monthly consumption in kWh. Then divide by 30 to get daily consumption, and divide that by your location's average peak sun hours (adjusted for system losses) to get the required system size in kWp. Our calculator automates this entire process — just enter your bill amount, rate, and local sun hours.
How many solar panels do I need to offset my electricity bill?
The number of panels depends on your energy consumption and local sun hours. On average, a household may need between 10 to 30 panels of 400W each to fully offset their electricity usage. Use our calculator above by entering your monthly bill, electricity rate, and peak sun hours to get a personalized estimate of the exact number of panels needed for your situation.
What is kWp and how does it relate to solar panel output?
kWp (kilowatt-peak) is the maximum power output of a solar system under standard test conditions (1000 W/m² irradiance, 25°C cell temperature). It represents the rated capacity of your solar installation. Your actual daily energy production in kWh depends on kWp multiplied by local peak sun hours and adjusted for system losses (inverter efficiency, wiring, temperature, dust, etc.).