Motor Run Hours for an Energy Budget
The inverse of the motor-cost tile: the run hours an annual energy budget buys, hours = budget / (input_kW x rate), input_kW = HP x 0.746 x load / efficiency. A 25 HP motor at 93% and $0.12/kWh draws 20.05 kW, so a $5,000 budget covers about 2,078 hours. Answers 'how long can I run it' instead of the cost from a set duty. Energy charge only; the utility tariff (demand, time-of-use, power-factor) governs the full bill, so the real hours are fewer.
Formula and source
input_kW = HP x 0.746 x (load_factor/100) / (efficiency/100); max_hours = cost_budget / (input_kW x rate); annual_kWh = input_kW x max_hours. The inverse of annual_cost = input_kW x run_hours x rate.
First-principles electrical-input power and the 0.746 kW-per-HP identity, solved for the run hours.
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