I recently purchased a portable generator that is 7 hp and 3050 continuous watts, i tried to calculate the efficiency as follows:743 watts 1 hp7 X 743 5201 watts, (so at 100 percent efficiency, 5201 watts is possible to produce from a 7 hp generator.)the unit produces 3050 watts, so the 5201 watts (possible watts)/3050(actually produced watts) (0.5864) or approximately 59% efficiency, this does not seem right, it should be about half that.What am i doing wrong?
You are calculating only the shaft horsepower to electric power output efficiency. That is separate and different from the internal combustion engine efficiency. Calculate that by comparing the fuel used and its heat content and its ability to do work versus the shaft horsepower.
First, nothing operates at 100% efficiency. You are converting angular rotation into electric power and in any conversion of power, you lose efficiency. 59% efficiency isn't that bad. Second, generators are measured at continuous power and peak power. Check your owners manual or look on the side of the generator. At peak power, you will find that the efficiency is greater.
That is correct, but it measures efficiency from mechanical output of the engine to electrical output. It does NOT include the efficiency from gasoline (or diesel) fuel all the way to electricity. You need additional information to get that, such as gallons per hour or per day used by engine when operating at full output.
