DC-to-AC derate factor
The combined system losses that shrink a panel's DC nameplate rating down to usable AC power — a standard default is about 0.86 (a 14% loss).
Solar panels are rated in DC watts under lab conditions, but your home uses AC power, and real systems lose energy along the way — in the inverter, wiring, connections, soiling, and temperature. The DC-to-AC derate factor rolls all of those into one multiplier.
NREL's PVWatts uses a default derate of about 0.86, meaning roughly 14% of the DC nameplate is lost before it becomes household AC. It's a key input when translating system size into expected kilowatt-hours.
Put it to work
See also