Calculate system kilowatts, output, and roof area. Compare savings, payback, inverter size, and performance losses. Create quick reports for smarter rooftop energy planning today.
| Case | Monthly Usage (kWh) | Peak Sun Hours | Losses (%) | Approx. System Size (kW) | Approx. Panels at 550W | Approx. Roof Area (m²) |
|---|---|---|---|---|---|---|
| Small Home | 450 | 5.5 | 20 | 3.75 | 7 | 16.10 |
| Family Home | 900 | 5.5 | 20 | 7.70 | 14 | 32.20 |
| Small Shop | 1500 | 5.8 | 18 | 11.55 | 21 | 48.30 |
Daily usage = Monthly usage ÷ 30
Target daily solar need = Daily usage × Desired coverage
Effective sun hours = Peak sun hours × (1 − System losses)
Required system size = Target daily solar need ÷ Effective sun hours
Recommended system size = Required system size × 1.10 buffer
Panel count = Recommended system size × 1000 ÷ Panel wattage
Monthly generation = Actual DC size × Peak sun hours × (1 − Losses) × 30
Required roof area = Panel count × Panel area
Monthly savings = Self-used energy × Tariff + Exported energy × Export credit
Simple payback = Installed cost ÷ Net annual benefit
Battery size = Critical load × Backup hours ÷ (Depth of discharge × Battery efficiency)
These formulas help estimate solar size, energy output, roof need, operating value, and backup storage. Final design should still consider shade, local weather, wiring path, inverter choice, structure, and utility rules.
A kilowatt solar system calculator helps you size a rooftop PV setup with fewer guesses. It turns electricity usage into a practical system recommendation. You can estimate required solar capacity, expected generation, roof area, panel count, inverter size, savings, and payback. This makes early planning easier for homes, offices, farms, and small shops.
An undersized system leaves a large utility bill. An oversized system may waste money and roof space. Good sizing balances energy demand, local sun hours, panel efficiency, system losses, and budget. It also improves equipment selection. You can match solar panels, inverter capacity, and battery backup more accurately.
Monthly energy use is the starting point. Peak sun hours affect daily production. Desired coverage lets you plan partial or full offset. System losses include temperature, dirt, wiring, and inverter losses. Panel wattage changes panel count. Panel area and usable roof percentage affect layout feasibility. Tariff, installed cost, and yearly maintenance costs shape savings and payback.
The recommended system size shows the estimated DC capacity in kilowatts. Panel count shows how many modules you may need. Estimated monthly and annual generation show expected energy output. Roof checks show whether your available space can support the design. The inverter estimate helps you choose a practical AC rating. Battery results support essential load backup planning.
Use realistic sun hours for your city. Add sensible system losses. Keep some roof margin for walkways and maintenance. Choose panel wattage that fits your structure and shading pattern. Compare full offset and partial offset scenarios before buying. Review payback with conservative tariff assumptions. A careful estimate today can prevent expensive changes after installation.
This tool suits homeowners comparing rooftop options, businesses planning bill reduction, and installers preparing quick pre-sales estimates. It is also useful for checking whether roof area, system coverage, and backup goals fit together. The calculator does not replace a site survey, but it gives a strong first estimate before detailed engineering, structure review, and final equipment selection for real world rooftop planning decisions.
kW means kilowatts. It shows the power rating of the solar array. A higher kW system can usually produce more electricity under good sunlight.
Usually, yes. Higher wattage panels can reduce panel count for the same system size. However, dimensions, roof shape, shading, and budget still matter.
Losses make the estimate more realistic. Heat, dust, cable resistance, inverter conversion, and mismatch reduce actual energy compared with nameplate output.
No. It gives a strong early estimate. Final design should still check shading, roof structure, orientation, utility rules, equipment availability, and installer recommendations.
Peak sun hours express the equivalent number of full sun hours in a day. They are used to estimate daily and annual solar energy production.
A system may fit electrically but not physically. Roof area checks whether your chosen panel count can actually fit within usable installation space.
Yes. This version subtracts annual O&M cost from annual savings before estimating simple payback, which gives a more realistic financial picture.
Add batteries when backup during outages matters or when you want to support critical loads. Battery sizing should match backup hours, depth of discharge, and efficiency.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.