Plan a resilient solar-plus-grid power setup easily. Compare backup targets, efficiencies, and safety margins quickly. Get clear sizing outputs for your home or shop.
| Appliance | Qty | Watts each | Hours/day | Daily kWh |
|---|---|---|---|---|
| LED lights | 10 | 9 | 5 | 0.45 |
| Ceiling fans | 4 | 60 | 6 | 1.44 |
| Refrigerator | 1 | 120 | 10 | 1.20 |
| TV | 1 | 90 | 4 | 0.36 |
| Laptop | 2 | 60 | 5 | 0.60 |
| Water pump (surge load) | 1 | 750 | 1 | 0.75 |
| Total (example) | — | — | — | 4.80 |
Start with total daily use in kWh/day and confirm the highest concurrent watts. If a home uses 10 kWh/day and peaks at 1.8 kW, a 75% solar coverage target plans to supply 7.5 kWh/day from sunlight while the grid covers the remainder. Use surge watts for pumps and compressors, often 2–4× running watts for a few seconds.
Peak sun hours translate location and season into production. At 5.0 PSH, a 4.0 kW array produces about 4.0×5.0=20 kWh DC before losses. Apply a derate of 0.75–0.85 for heat, wiring, dust, and tilt, then inverter efficiency near 0.90–0.96 to estimate AC energy delivered. This calculator combines those factors for daily output.
Hybrid systems size batteries for critical loads, not the whole home. If backup load is 40% of 10 kWh/day and autonomy is 1.5 days, the backup target is 6.0 kWh. Battery capacity increases when depth of discharge is limited: 80% DoD requires 6.0/0.80=7.5 kWh before efficiency adjustments. Round-trip efficiency typically ranges 0.85–0.95 depending on chemistry and operating temperature.
Select an inverter for continuous load with margin and for surge events. A 2.0 kW peak with a 1.25 margin suggests 2.5 kW continuous capacity. If surge is 4.0 kW, choose equipment that can supply at least that surge rating. Extra headroom reduces nuisance trips, supports future appliances, and helps in hot climates where electronics de-rate.
Costs are split into panels, batteries, inverter, and balance-of-system. Many projects add 10–25% for mounting, cabling, protection, and labor. Savings depend on the kWh actually offset; the model caps offset at your daily load. A useful check is comparing annual savings to total cost: lower electricity rates or small offsets lengthen payback, while higher usage and strong PSH improve it. Run first two scenarios conservative winter PSH and dusty derate, then optimistic summer values; the spread usually shows whether you need more panels or simply adjust backup load targets.
Use solar maps or installer data for your city, then choose an annual average. For conservative sizing, use the lowest-season average. Small changes matter: dropping from 5.0 to 4.0 PSH requires about 25% more array power.
A common planning range is 0.75–0.85. Use lower values for hot roofs, dusty areas, long cable runs, or partial shading. If panels are cleaned often and wiring is short, a higher derate can be reasonable.
Hybrid systems often keep the grid for heavy loads or cloudy weeks. Targeting 60–90% can reduce battery size and cost while still offsetting most energy. You can raise coverage later by adding modules if space allows.
Match it to battery chemistry and warranty guidance. Lead-acid is often planned at 50% DoD, while lithium systems commonly use 80–90%. Lower DoD extends cycle life but increases required capacity.
Add the start-up surge of the largest motor load that may start while other loads run. Pumps and compressors can be 2–4× running watts. Check appliance nameplates or measured data when possible.
Treat it as a minimum rating estimate. Select the next higher standard controller size, then validate with module Voc/Isc, string configuration, temperature corrections, and local electrical rules. Your installer can confirm final wiring and protection.
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.