How do you calculate a motor's annual energy cost?

Convert horsepower to kW (hp x 0.746), multiply by the load fraction, divide by efficiency to get input kW, multiply by annual runtime hours for kWh, then multiply by your rate. A 25 hp motor at 92% efficiency and 70% load draws 14.19 kW, uses 45,409 kWh over 3,200 hours, and costs about $5,449/yr at $0.12/kWh.

What is a good motor efficiency?

Standard-efficiency motors run roughly 87-90%, NEMA Premium motors hit 92-95% in the 10-50 hp range, and IE4/IE5 designs push higher. The example's 92% is solid NEMA Premium territory; older rewound motors can sag below 88%, which directly inflates the input kW and the bill.

Does running a motor at partial load save money?

Yes, but not proportionally. Input power scales with load, so 70% load draws roughly 70% of full-load power. However, motor efficiency dips at very light loads (below ~40%), so an oversized motor loafing at 30% can be less efficient and waste money despite the lower absolute draw.

How much does a 25 hp motor cost to run per year?

At 70% load, 92% efficiency, 3,200 hours, and $0.12/kWh it runs about $5,449/yr, or roughly $1.70 per operating hour. Double the runtime to 6,400 hours and you roughly double the cost; a 24/7 schedule of ~8,760 hours would land near $14,900/yr.

Is it worth replacing a motor to save energy?

Compare annual cost at the old efficiency versus the new one. Going from 88% to 95% on this duty cuts input kW by about 7%, saving roughly $400/yr; against a $1,500 premium that's under a 4-year payback, which most energy programs and rebates make worthwhile, especially for high-runtime motors.

Why divide by efficiency instead of multiplying?

Horsepower is the mechanical output the motor delivers to the load. The electrical input is always larger because some power is lost as heat, so input kW = output kW / efficiency. A 92% motor needs about 8.7% more input than its shaft output, which is the energy you actually pay for.

Energy calculator

Motor Energy Cost Calculator

Motor energy cost is the annual electricity bill a single AC motor racks up while doing useful work, derived from its rated horsepower, how hard it actually runs, how efficiently it converts power, and your utility rate. Plant engineers, energy managers, and maintenance reliability teams use it to rank which motors deserve a premium-efficiency replacement or a VFD. Motors are the largest single electricity consumer in most factories, so a few percentage points of efficiency on a 24/5 motor compounds into thousands of dollars a year. Knowing the number per motor turns a vague 'electricity is expensive' complaint into a ranked capital plan.

What this calculator does

Calculate electric motor kWh and cost from horsepower, efficiency, load, runtime, and electric rate.
Use when estimating energy cost for pumps, fans, conveyors, compressors, and driven equipment.
It converts a motor's nameplate horsepower, operating load, efficiency, and annual runtime into yearly energy use (kWh) and electricity cost at your utility rate.

Formula used

Input kW = horsepower × 0.746 × load ÷ efficiency
Annual energy = input kW × annual runtime
Annual cost = annual energy × electricity rate

Inputs explained

Motor horsepower: undefined
Motor efficiency: undefined
Average load: undefined
Runtime: undefined
Electricity rate: undefined

How to use the result

Use it when building an energy audit, justifying a premium-efficiency or VFD upgrade, or comparing two motors for the same duty.
It assumes a fairly constant average load; for motors with wildly variable duty cycles or frequent starts, a metered kWh reading will be more accurate than this point estimate.

Current U.S. benchmarks

As of Apr 2026, industrial electricity averages 8.7 cents per kWh across the U.S. (EIA), up 5.5% from a year earlier. State averages range widely, so plants should confirm against their own tariff.
U.S. manufacturing runs at 75.6% of capacity (Federal Reserve, May 2026). New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate a motor's annual energy cost? Convert horsepower to kW (hp x 0.746), multiply by the load fraction, divide by efficiency to get input kW, multiply by annual runtime hours for kWh, then multiply by your rate. A 25 hp motor at 92% efficiency and 70% load draws 14.19 kW, uses 45,409 kWh over 3,200 hours, and costs about $5,449/yr at $0.12/kWh.
What is a good motor efficiency? Standard-efficiency motors run roughly 87-90%, NEMA Premium motors hit 92-95% in the 10-50 hp range, and IE4/IE5 designs push higher. The example's 92% is solid NEMA Premium territory; older rewound motors can sag below 88%, which directly inflates the input kW and the bill.
Does running a motor at partial load save money? Yes, but not proportionally. Input power scales with load, so 70% load draws roughly 70% of full-load power. However, motor efficiency dips at very light loads (below ~40%), so an oversized motor loafing at 30% can be less efficient and waste money despite the lower absolute draw.
How much does a 25 hp motor cost to run per year? At 70% load, 92% efficiency, 3,200 hours, and $0.12/kWh it runs about $5,449/yr, or roughly $1.70 per operating hour. Double the runtime to 6,400 hours and you roughly double the cost; a 24/7 schedule of ~8,760 hours would land near $14,900/yr.
Is it worth replacing a motor to save energy? Compare annual cost at the old efficiency versus the new one. Going from 88% to 95% on this duty cuts input kW by about 7%, saving roughly $400/yr; against a $1,500 premium that's under a 4-year payback, which most energy programs and rebates make worthwhile, especially for high-runtime motors.

Last reviewed 2026-05-12.