Quick answer: Franklin Electric publishes well pump watts outright: 670 W for 1/2 HP, 940 W for 3/4 HP and 1,210 W for 1 HP at 230 V. Doubling the horsepower does not double the watts. And each one is rated to run continuously 32 to 43 percent higher than that.
Most well pump wattage guides multiply the nameplate amps by the voltage and print the result. They do not need to. Franklin Electric, whose motors sit inside pumps sold under many different brand names, publishes the actual input watts for every model it makes, in a manual anyone can download.
This load has the most violent startup in our appliance wattage chart, and it is the one people most often get wrong in both directions. Here are the published figures, and the two numbers beside them that matter more.
Well pump watts: 1/2 HP vs 3/4 HP vs 1 HP, as published
| Rating | Volts | Full load amps | Running watts | Max continuous watts | Power factor | Locked rotor amps |
|---|---|---|---|---|---|---|
| 1/2 HP | 230 | 5.0 | 670 W | 960 W | 58 % | 32.2 |
| 3/4 HP | 230 | 6.8 | 940 W | 1,310 W | 62 % | 40.7 |
| 1 HP | 230 | 8.2 | 1,210 W | 1,600 W | 63 % | 48.7 |
| 1/2 HP | 115 | 10.0 | 670 W | 960 W | 58 % | 64.4 |
| 1.5 HP | 230 | 10.6 | 1,710 W | 2,280 W | 76 % | 66.2 |
Note what the power factor column does to the usual shortcut. Multiply 5.0 A by 230 V and you get 1,150, which is apparent power, not watts. Franklin’s own figure is 670 W, and its own published power factor of 58 percent is exactly why.
Well pump watts do not scale with horsepower
Go from 1/2 HP to 1 HP and you double the horsepower. The watts rise by a factor of 1.81, not 2. Step up to 3/4 HP, a 50 percent increase in rating, and the watts rise 40 percent.
The reason is in the same table Franklin prints the watts in: efficiency climbs with size. These three motors are rated 56, 59 and 62 percent at full load. The bigger motor wastes proportionally less, so its consumption lags behind its rating.
Two practical consequences. Upgrading a pump costs less in running electricity than the horsepower jump suggests. And a small motor is not the efficient choice people assume; it is simply a smaller one.
The number nobody quotes: the service factor
Every one of these motors carries a service factor above 1.0, which means the manufacturer rates it to run continuously above its nameplate load. The 1/2 HP motor has a service factor of 1.6. Its maximum continuous draw is not 670 W. It is 960 W.
That is 43 percent above the figure every chart quotes, and a pump lifting from a deep well against a full pressure tank will spend real time up there. If you size a generator or a battery to 670 W because that is the number you found, you have sized it to the motor’s easiest day.
Usefully, that margin shrinks as the motor grows. The smallest motor is the one whose real ceiling sits furthest from its label, which is the opposite of the assumption most sizing guides make.
Starting is a different problem entirely
The locked rotor column is the one that decides whether your backup equipment works at all. At 230 V those figures come to 7,406 VA for the 1/2 HP, 9,361 for the 3/4 and 11,201 for the 1 HP.
Against 670 W of running draw, that is a startup demand roughly eleven times larger. Nothing else in a house behaves like this. It is why a well pump defeats power stations that run a whole kitchen, and why sizing on running watts alone fails here more expensively than anywhere else.
One counterintuitive detail: the ratio improves as the motor grows. The 1/2 HP demands about eleven times its running watts to start, the 1 HP about nine. Stepping up a size does not make your surge problem proportionally worse, and the surge ratings a battery answers it with step up too.
This is the opposite of what we found in the sump pumps in the same silo, where locked rotor current runs only 1.5 to 2.9 times full load. Those use permanent split capacitor motors; these are split phase, and the difference is enormous. The motor technology decides the surge, not the fact that both are pumps.
115 V and 230 V are the same pump
Franklin lists the 1/2 HP motor in both. The 115 V version draws 10.0 A where the 230 V draws 5.0, and its locked rotor is 64.4 A against 32.2. Double the current in both cases.
But the running watts are identical at 670 W, and the starting demand works out to the same 7,406 VA either way. Voltage changes the wire and the breaker you need, not the power. A 230 V installation is easier on the cable, not cheaper to run.
What it costs to run
At the June 2026 US residential average of 18.34 cents per kWh, the 1/2 HP costs 12.3 cents an hour of actual pumping, the 3/4 HP 17.2 cents and the 1 HP 22.2 cents. In the UK, at the Ofgem capped 26.11 p, that is 17.5p, 24.5p and 31.6p.
A pump that runs two hours a day costs about $7.37 a month at 1/2 HP and $13.31 at 1 HP. Like the sump pump, this is a sizing problem rather than a running cost problem. It is the surge that costs money, in equipment.
Safety. A submersible well pump is hard-wired 230 V equipment at the bottom of a well. Nothing in this article is an instruction to work on one. Read the figures off the paperwork or the pressure-switch box cover, and leave the wiring, the control box and the pitless adapter to a licensed well contractor or electrician.
If you are running the pump from a generator during an outage, the generator goes outside, well away from windows, doors and vents: carbon monoxide from a portable generator kills quickly and without warning. Connecting one to house wiring needs a transfer switch installed under NEC Article 702; in the UK the equivalent work falls under BS 7671. We describe the equipment; we do not tell you how to wire it.
Frequently asked questions
How many watts does a 1/2 HP well pump use?
Franklin publishes 670 W at full load for its 4 inch 2 wire motor, at either 115 V or 230 V. Its maximum continuous rating is 960 W. Charts quoting 1,150 W have multiplied 5 amps by 230 volts and printed apparent power.
What size generator do I need for a well pump?
Size it on the locked rotor figure, not the running watts. A 1/2 HP motor asks for about 7,400 VA at the instant it starts. Many generators and almost no small power station will deliver that, which is why soft starters exist for this load.
Does a 1 HP pump use twice the electricity of a 1/2 HP?
No, about 1.81 times. Franklin rates the larger motor at 62 percent efficiency against 56 for the smaller, so its consumption rises more slowly than its horsepower. It also does more work per hour, so it may run for less time.
Is a 230 V pump cheaper to run than a 115 V one?
No. Franklin lists both at the same 670 W. The 230 V version draws half the current, which allows thinner cable over a long run and a smaller breaker, but the energy consumed is identical.
My pump is not a Franklin. Do these figures still apply?
Treat them as a well-sourced starting point rather than your pump’s numbers. Franklin motors are used across many pump brands, so the badge on the pump often is not the badge on the motor. Find the motor model number and read its own plate before you commit money.
This article is general information, not an installation guide and not a substitute for a licensed electrician. Electrical work on a service panel, a transfer switch or a utility connection is regulated in most jurisdictions and normally requires a permit and an inspection. Fuel-burning equipment produces carbon monoxide and must never be run indoors, in a garage or near an opening into the home.
