Plan solar capacity for reliable peak demand coverage. Compare scenarios with adjustable efficiencies and sun. Download results as CSV or PDF for sharing easy.
| Load item | Watts | Hours/day | Daily Wh | Notes |
|---|---|---|---|---|
| Ceiling fans (3) | 210 | 8 | 1680 | 70 W each |
| LED lighting | 120 | 6 | 720 | Whole home estimate |
| Refrigerator | 150 | 10 | 1500 | Compressor cycles |
| TV + router | 130 | 6 | 780 | Entertainment + internet |
| Water pump | 750 | 0.5 | 375 | High surge load |
| Totals | 1360 | — | 5055 | ≈ 5.06 kWh/day |
Use the totals to estimate daily energy and identify peak watts for inverter sizing.
Peak load is the highest simultaneous running demand you expect. The calculator multiplies peak watts by a surge factor and a headroom margin to estimate inverter size. For example, 2500 W with a 1.25 surge factor and 1.15 headroom suggests about 3594 W. Increase surge factor for pumps, compressors, and tools.
Daily energy in kWh drives the solar array. The model converts kWh to required panel power by dividing by peak sun hours and an overall derating factor. With 8 kWh per day, 5 sun hours, and 0.75 derating, the base array is 2.13 kW, then headroom increases it. Lower sun hours in winter can push array size higher, even if peak watts stay unchanged.
Derating captures real losses from heat, dust, wiring, tilt, and conversion. A derate of 0.75 assumes only seventy five percent of nameplate output is usable. Peak sun hours represent average daily full sun equivalents. Headroom reduces energy shortfall risk and helps cover gradual panel aging. Use higher headroom when shading, soiling, or seasonal variability is common.
Battery sizing targets energy, not power. Nominal storage is estimated from daily kWh, autonomy days, depth of discharge, and efficiency assumptions. If autonomy is 1 day, DoD is 0.80, battery efficiency is 0.90, and inverter efficiency is 0.92, nominal battery is roughly daily_kWh ÷ (0.80×0.90×0.92). Higher autonomy, lower DoD, or lower efficiency increases kWh and amp hours at the selected system voltage.
Use PV kW and panel count to compare modules, mounting, and wiring costs. Inverter watts help shortlist models that meet surge needs and continuous demand. Battery kWh and Ah help map bank options, such as series strings for 48 V systems. Controller current estimates indicate minimum rating; select the next standard size and confirm input voltage limits. Validate with datasheets.
Q1: What inputs most affect panel count?
Daily energy, peak sun hours, and derating drive array size. Higher kWh, lower sun hours, or lower derate increases required PV watts, which increases panel count when divided by the chosen panel wattage and rounded up.
Q2: How should I choose surge factor?
Use 1.0 for mostly resistive loads. For refrigerators, pumps, and compressors, start around 1.25 to 2.0 depending on motor size. If nuisance trips occur, increase surge factor and headroom together.
Q3: Does system voltage change energy sizing?
Voltage does not change kWh needs, but it changes current. Higher voltage reduces current for the same PV power and battery energy, which can simplify wiring and controller selection. Match voltage to your inverter and battery configuration.
Q4: Why is there a derating factor?
Nameplate ratings assume ideal conditions. Derating accounts for heat, dust, wiring losses, angle mismatch, and conversion losses. Using a realistic derate improves reliability and reduces the chance of undersizing, especially in hot climates.
Q5: What does autonomy mean here?
Autonomy is the number of days you want to run from batteries when solar production is limited. Increasing autonomy increases required battery kWh and amp hours. Set autonomy to zero if you only want daytime operation.
Q6: Are the results final for purchasing?
No. The calculator gives planning estimates. Confirm equipment datasheets, temperature ratings, cable sizing, protection devices, and local code requirements with a qualified installer before buying or installing components.
This tool provides planning estimates only. Real sizing depends on equipment specs, wiring limits, surge behavior, climate, shading, and local electrical codes. Verify all selections with a qualified installer.
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.