--- title: "Solar Panel Calculator | Solar System Size Estimate | XTRAW Tools" description: "Estimate solar panel system size and panel count from electricity use and sun hours with a free browser-based calculator." url: "https://xtraw.com/tools/calculators/science-calculators/energy-calculators/solar-panel-calculator" date: "2026-05-22T00:36:22+00:00" language: "en-GB" --- [kW to kWh Calculator](https://xtraw.com/tools/calculators/science-calculators/energy-calculators/kw-to-kwh-calculator)[Kinetic Energy Calculator](https://xtraw.com/tools/calculators/science-calculators/energy-calculators/kinetic-energy-calculator) [![Solar Panel Calculator from XTRAW Tools](https://xtraw.com/images/virtuemart/product/xtraw-solar-panel-calculator-360x360.jpg)](https://xtraw.com/images/virtuemart/product/xtraw-solar-panel-calculator-360x360.jpg "Solar Panel Calculator from XTRAW Tools") popular [Back to: Energy Calculators](https://xtraw.com/tools/calculators/science-calculators/energy-calculators "Energy Calculators") # Solar Panel Calculator Estimate solar panel system size needed from electricity use, sun hours, panel wattage, and efficiency. Use this free browser-based solar panel calculator from XTRAW Tools. **Solar Panel Calculator** helps you estimate solar panel system size needed from electricity use, sun hours, panel wattage, and efficiency. Use this free browser-based calculator from XTRAW Tools to compare inputs, estimate results, and plan your next step. ## How to Use the Solar Panel Calculator 1. Enter the required calculator inputs shown in the form. 2. Review the measurements, electrical values, grades, weights, rates, or reading assumptions. 3. Run the calculator, then adjust one input at a time to compare scenarios or check your work. ## What This Calculator Helps With Estimate solar panel system size needed from electricity use, sun hours, panel wattage, and efficiency. It is designed for homeowners, solar shoppers, energy planners, students, and people comparing solar system estimates who want a fast, browser-based estimate before relying on a contractor, electrician, engineer, code authority, teacher, advisor, or professional source. - Monthly Electricity Usage: 900 kWh - Peak Sun Hours: 5/day - Panel Wattage: 400 W - System Efficiency: 80% ## Common Uses People use this calculator when they need a quick way to estimate construction materials, electrical values, solar sizing, school grades, GPA, or reading time from real inputs. - **Project Planning:** Compare project assumptions, academic goals, energy plans, or electrical scenarios. - **Budgeting:** Estimate costs, savings, energy use, materials, or planning targets. - **Measurement:** Use measurements, grades, electrical values, or reading values to get a clear result. ## Formula or Method System kW = Daily kWh / (Sun Hours × Efficiency); Panels = System W / Panel W. ## Example **Example inputs:** Monthly Electricity Usage: 900 kWh; Peak Sun Hours: 5/day; Panel Wattage: 400 W; System Efficiency: 80% **Example result:** Using the default inputs, estimated system size is 7.50 kW and about 19 panels. ## Related Tools - [Electricity Cost Calculator](https://xtraw.com/tools/electricity-cost-calculator) - [kW to kWh Calculator](https://xtraw.com/tools/kw-to-kwh-calculator) - [Energy Conversion Calculator](https://xtraw.com/tools/energy-conversion-calculator) - [Watts To Amps Calculator](https://xtraw.com/tools/watts-to-amps-calculator) - [Wire Size Calculator](https://xtraw.com/tools/wire-size-calculator) - [kVA Calculator](https://xtraw.com/tools/kva-calculator) ## Solar Panel Calculator FAQ ### Is the Solar Panel Calculator free? Yes. This calculator is free to use on XTRAW Tools. ### Do I need to create an account? No. XTRAW tools are designed for browser-based use without requiring an account. ### Are the results exact? Results may be estimates depending on the inputs, formula, rounding, assumptions, and purpose of the calculator. Always verify important results before relying on them. **Disclaimer:** This calculator is provided for general informational, educational, and convenience purposes only. It is not legal, financial, medical, tax, engineering, electrical, construction, solar, academic, safety, or professional advice. Always verify important results with a qualified professional, instructor, code authority, manufacturer documentation, or authoritative source before making decisions. **Related Products** ![Tooltip]() [![Electricity Cost Calculator from XTRAW Tools](https://xtraw.com/images/virtuemart/product/resized/xtraw-electricity-cost-calculator-360x360_230x230.jpg) Electricity Cost Calculator](https://xtraw.com/tools/calculators/science-calculators/energy-calculators/electricity-cost-calculator "Electricity Cost Calculator") Calculate the cost of running an appliance from watts, runtime, days, and rate. Use this free browser-based electricity cost calculator from XTRAW Tools. Custom prototype for related products [![kW to kWh Calculator from XTRAW Tools](https://xtraw.com/images/virtuemart/product/resized/xtraw-kw-to-kwh-calculator-360x360_230x230.jpg) kW to kWh Calculator](https://xtraw.com/tools/calculators/science-calculators/energy-calculators/kw-to-kwh-calculator "kW to kWh Calculator") Convert kilowatts to kilowatt-hours and estimate energy cost. Use this free browser-based kw to kwh calculator from XTRAW Tools. Custom prototype for related products [![Energy Conversion Calculator from XTRAW Tools](https://xtraw.com/images/virtuemart/product/resized/xtraw-energy-conversion-calculator-360x360_230x230.jpg) Energy Conversion Calculator](https://xtraw.com/tools/converters/unit-converters/energy-converters/energy-conversion-calculator "Energy Conversion Calculator") Convert energy values between joules, calories, kilowatt-hours, BTU, watt-hours, and other units. Use this free browser-based energy conversion calculator from XTRAW Tools. Custom prototype for related products [![Watts to Amps Calculator from XTRAW Tools](https://xtraw.com/images/virtuemart/product/resized/xtraw-watts-to-amps-calculator-360x360_230x230.jpg) Watts to Amps Calculator](https://xtraw.com/tools/calculators/science-calculators/energy-calculators/watts-to-amps-calculator "Watts to Amps Calculator") Convert watts to amps and estimate current from voltage and power factor. Use this free browser-based watts to amps calculator from XTRAW Tools. Custom prototype for related products [![Wire Size Calculator from XTRAW Tools](https://xtraw.com/images/virtuemart/product/resized/xtraw-wire-size-calculator-360x360_230x230.jpg) Wire Size Calculator](https://xtraw.com/tools/calculators/science-calculators/wire-size-calculator "Wire Size Calculator") Determine a wire gauge estimate from current, distance, voltage, and voltage drop limit. Use this free browser-based wire size calculator from XTRAW Tools. 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