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Click "Calculate Wire Gauge" after the system calculator has run.
Fuse/breaker recommendations appear after calculation.
Enter your appliances and we'll calculate the exact solar panel array, battery bank, inverter, and charge controller you need.
All calculations include standard system losses (wiring, charge controller efficiency, inverter losses).
Pick a preset to load typical appliances, or skip and add your own below.
The duty cycle accounts for appliances that don't run at full power continuously. A refrigerator compressor cycles on/off (~35% of the time); a lamp stays on 100%.
| Appliance | Peak Watts | Duty Cycle % | Hours/Day | Wh/Day | |
|---|---|---|---|---|---|
| Daily Total: | 0 Wh | ||||
Start by adding up the daily watt-hours (Wh) of every appliance you plan to run, then multiply by 1.2 for system losses. Divide that total by the peak sun hours in your location (typically 4–5 PSH in the US) to get the solar array wattage. For batteries, multiply daily Wh by your desired days of autonomy and divide by usable depth-of-discharge (80% for LiFePO4). The calculator above does all of this automatically based on your appliance list.
For typical off-grid use, plan for 2–3 days of autonomy (battery covers usage with no solar input). A small cabin using 2 kWh/day needs roughly 5–8 kWh of LiFePO4 storage. A full-time off-grid home using 15 kWh/day needs 35–50 kWh. Lead-acid (AGM) needs roughly double that capacity because of shallower depth of discharge.
Use 12V for systems under 1,500 W of solar (RVs, vans, small cabins). Use 24V for 1,500–4,000 W (medium cabins, tiny homes). Use 48V for anything 4,000 W or larger (full off-grid homes, EV charging). Higher voltage means lower current, which means thinner wiring and lower losses. The calculator picks the optimal voltage automatically based on your load.
Match your inverter to your largest expected continuous load with 25% headroom. If your biggest single appliance is a 1,500 W microwave, choose at least a 2,000 W inverter. For surge loads (well pumps, AC compressors, table saws) check the LRA (locked-rotor amps) — the inverter needs to handle 2–3× the running watts for a few seconds. The calculator suggests inverter size based on your maximum simultaneous load.
Use MPPT for any system over 200 W. MPPT extracts 20–30% more energy from your panels and lets you wire panels in series at higher voltage (smaller wires, more flexibility). PWM only makes sense for very small systems where the cost difference matters and the panel voltage matches battery voltage. The calculator recommends MPPT controllers sized to your array.
Total panel wattage needed = (daily Wh × 1.2 loss factor) ÷ peak sun hours. For an average US home using 30 kWh/day at 4.5 PSH, that’s about 8 kW of panels (20 × 400W panels). A small cabin using 2 kWh/day needs about 550 W (2 × 300W panels). The calculator above gives an exact array size for your appliance list and location.