Thumbing through the Onan manual looking for recommended maintenance items and came across this.
Interesting. Never realized the power loss was so great.
We spend lots of time at 9-11,000’.
Effects Of High Altitude And Extreme
Temperatures
If you travel at high altitudes or in extreme temperatures, your generator can lose power. In such lower-density air conditions, you can’t operate as many electrical devices as you could under normal operating conditions.
Power decreases 3.5% for each 1,000 feet above an altitude of 500 feet. For example, to operate at 4,500 feet (4,000 feet above rated generator altitude) multiply 3.5% x 4 (4,000 ft) = 14% power loss. Then multiply .14 x your generator’s power rating: 4,000 watts x .14 = a loss of 560 watts at that altitude.
Power decreases in extreme temperatures by 1% for each 10°F (5.5°C) above 77°F (25°C).