How much real output your generator loses to elevation and heat, by engine type.
1 · Your generator
Engine type2 · Your environment
3 · Optional: what do you need to run?
Real-world output
| Altitude derate | — |
| Temperature derate | — |
Engines are rated at standard conditions (about 77°F and near sea level, per ISO 8528). Thinner air at altitude and hotter air both reduce the oxygen available for combustion, so the engine makes less power. Naturally-aspirated and inverter engines lose roughly 3.5% per 1,000 ft above ~1,000 ft; turbocharged engines lose far less (~1.5%) and only above a higher threshold. Both lose about 1% per 10°F above 77°F.
Estimates using standard derating rules of thumb; your engine's actual derate curve is in its manual and varies by model, fuel, and cooling. Most portable generators are naturally aspirated; many large standby units are turbocharged and derate less. Use this for planning and verify against the manufacturer's altitude/temperature curves.