Generator Derating Calculator

Why Does Generator Power Derate?

A generator's power output is rated under ideal factory conditions: typically at sea level and around 60°F (15.5°C). When you operate a generator in the real world, environmental conditions change its performance. This reduction in power is called derating.

• Altitude: As you go higher, the air becomes thinner. This means there is less oxygen available for the engine to burn fuel efficiently. A good rule of thumb is a 3.5% power loss for every 1,000 feet above sea level (or a manufacturer-specified baseline, often ~500 ft).
• Temperature: Hotter air is less dense than cool air. Similar to high altitude, this reduces the amount of oxygen available for combustion, leading to a power loss. A common rule is a 1% power loss for every 10°F above the standard temperature (usually 60°F).

It's critical to account for derating to ensure your generator can actually handle your required load at your specific location and climate.