Work out farm electricity cost instantly with clear inputs, formula shown and shareable results.
Energy is connected load x hours x days, but the meter records input energy, which exceeds shaft output by the motor and drive losses — a load factor of about 0.85 for a well-matched induction motor pump set. Multiplying billed units by the tariff gives the cost for the season.
Farm electricity cost
Shaft kWh = kW x hours x days; billed units = shaft kWh / motor efficiency; cost = billed units x tariff
Motor and pump inefficiency, cable losses and any power factor penalty. An old rewound motor can run at 70% efficiency, adding 20% to the bill for the same water delivered.
Where a flat horsepower-based tariff applies, metered energy cost is irrelevant, but the incentive to fix leaks and worn pumps disappears. Check which tariff category applies to your connection.