Array
PV Array Sizing
Start from twelve months of utility bills, not a roof. This calculator turns an annual kilowatt-hour target into an array size, a module count, and a DC/AC ratio, then tells you whether that ratio will clip power at noon.
What it asks for
- Annual production target (kWh/yr) — Pull it off 12 months of utility bills.
- Peak sun hours (h/day) — NREL PVWatts for the site. US range is roughly 3.5–6.0.
- System derate (%) — PVWatts default is 86% before soiling/shade. 80% is a safe field number.
- Module rating (W)
- Inverter AC rating (kW AC)
- Offset target (%)