I would like to calculate actual fuel consumption on a diesel generator used for power generation. The obvious answer would be to use a flow-meter, but for various reasons (including price!) that might not be practical. My question is, is it possible to use another indicator (such as engine hours, RPM, etc.) to accurately estimate the fuel consumption? Or in other words, if such methods are used, how inaccurate can/would they be and what are the reasons/factors for this?