HP to kWh Calculator
Horsepower is a rate; kilowatt-hours are a quantity. To get from one to the other you need running time — and, if you are paying the bill, motor efficiency too.
"How many kWh is 5 HP?" is a question with no answer as written, and that is not pedantry — it is the whole problem. Horsepower measures how fast energy is being used. A kilowatt-hour measures how much has been used. Converting between them requires a third number: how long the motor runs.
Why You Cannot Convert HP Straight to kWh
The comparison that makes this click is speed and distance. Asking how many kWh are in 5 HP is like asking how many miles are in 60 mph. The speed is meaningless as a distance until you say how long you drove.
Efficiency Is Where Most Estimates Go Wrong
A motor's horsepower rating is its mechanical output at the shaft, not what it pulls from the supply. Getting that output costs more than the output itself, because of losses in the windings, bearings and cooling fan.
A 5 HP motor delivers 3.73 kW of shaft power. At 90% efficiency it draws 3.73 ÷ 0.90 = 4.14 kW from the grid. Ignore efficiency and you understate the electricity bill by about 10% — more with older or smaller motors, which are typically less efficient.
| Motor size | Shaft kW | Typical efficiency | Input kW | kWh per 8 h |
|---|---|---|---|---|
| 1 HP | 0.75 | 80% | 0.93 | 7.5 |
| 3 HP | 2.24 | 87% | 2.57 | 20.6 |
| 5 HP | 3.73 | 90% | 4.14 | 33.1 |
| 10 HP | 7.46 | 91% | 8.19 | 65.6 |
| 25 HP | 18.64 | 93% | 20.05 | 160.4 |
| 50 HP | 37.28 | 94% | 39.66 | 317.3 |
Efficiency figures above are typical for standard industrial induction motors. Premium efficiency classes such as IE3 and IE4 run a few points higher, and the difference compounds quickly on a motor running continuous shifts.
Load Factor — Motors Rarely Run Flat Out
The calculation above assumes the motor is working at its full rated output. In practice most run at partial load: a pump throttled back, a conveyor half full, a compressor cycling. A motor at 70% load draws roughly 70% of full-load power, so a straight full-load calculation overstates real consumption.
If you know the actual load, scale the result accordingly. If you do not, the full-load figure is a reasonable worst case for budgeting. Bear in mind that efficiency itself falls away at very light loads, so a motor running at 25% capacity is disproportionately wasteful — a common reason oversized motors cost more to run than expected.
What It Costs to Run
Multiply the energy figure by your electricity rate. The numbers add up faster than most people expect on continuous duty:
| Motor | kWh per 8 h shift | Per month (22 shifts) | At 0.15 per kWh |
|---|---|---|---|
| 1 HP | 7.5 | 164 | 24.61 |
| 5 HP | 33.1 | 729 | 109.37 |
| 10 HP | 65.6 | 1,442 | 216.33 |
| 25 HP | 160.4 | 3,528 | 529.21 |
Horsepower-Hours Are a Different Thing Again
You may come across the unit horsepower-hour (hp·h), which genuinely is an energy unit — one horsepower sustained for one hour. That converts directly: 1 hp·h = 0.7457 kWh, no extra information needed. It is uncommon outside older engineering texts, but if a source quotes hp·h rather than hp, no running time is required.
To convert the power rating itself rather than energy, use our HP to kW calculator. For motor current draw, see HP to amps, and for sizing from electrical measurements the electric motor HP calculator.
Frequently Asked Questions
One horsepower is 0.7457 kW of shaft power — a rate, not an amount. Run for one hour it uses about 0.75 kWh of shaft energy, or roughly 0.93 kWh from the supply at 80% efficiency.
No. HP is a rate; kWh is a quantity. Converting requires running time — asking how many kWh are in 5 HP is like asking how many miles are in 60 mph.
A 5 HP motor produces 3.73 kW at the shaft and draws about 4.14 kW at 90% efficiency — roughly 33 kWh over an eight-hour shift.
Because the HP rating is shaft output, not electrical input. A motor always draws more than it delivers — ignoring efficiency understates consumption by around 10%, more on small or older motors.
A horsepower-hour (hp·h) is a genuine energy unit — one horsepower sustained for one hour. It converts directly: 1 hp·h = 0.7457 kWh.
Rarely. Most run at partial load, so real consumption is below the full-load figure. But efficiency drops at very light loads, so an oversized motor can be disproportionately expensive.
Multiply input kW by hours per day, by working days, by your rate. A 5 HP motor on eight-hour shifts for 22 days uses about 729 kWh a month.