DIY Solar Calculators

Estimates only. These are planning numbers, not a design. Always check manufacturer specs, the NEC and your local code, and have a licensed electrician review anything you tie into a panel.

1. Solar panel sizing

Daily use (Wh/day) Peak sun hours Derate / losses (%) Panel size (W)

Calculate

More: Solar panel sizing explained · Panel reviews

2. Inverter sizing

Loads running at the same time (W, including the motor's running watts) Largest motor, running watts Motor surge multiplier (×) Output voltage120V240V (split-phase)

Calculate

More: How to size your inverter · Inverter sizing explained · Soft starts: Tools and Accessories

3. Battery sizing

Daily use (Wh/day) Days of autonomy Depth of discharge (%) System voltage12V (12.8V LiFePO4)24V (25.6V)48V (51.2V)

Calculate

More: How to size your battery bank (adds ~10% inverter loss and 20–30% headroom) · Battery reviews

4. Voltage drop (wire sizing, copper)

Wire gauge (copper) One-way run length (ft) System voltage (V) Current (amps)

Calculate

Guideline: many DIY builders aim to keep drop at or under about 3%. This checks voltage drop only. It does not check ampacity, temperature rating, fuse size or conduit fill. More: 48V vs 24V vs 12V · Cable sizing & protection

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