How many watts does a well pump use? Franklin's motor table, running and locked rotor

A well pump is the appliance whose wattage matters least and whose start-up draw matters most, and Franklin Electric, which makes most of the motors in American wells, publishes both. A 1/2 HP motor runs at about 1,150 W and starts at about 7,400 VA; the second number is the one that decides the backup source. Here is the table for the common sizes, the duty cycle from real water use, and what it means for a battery or a generator. The sizing itself is on the well pump page.

Franklin’s numbers, by horsepower

Motor (Franklin 4-inch 2-wire, single phase)	Full load	Running watts	Locked rotor	Start, VA
1/3 HP, 230 V	4 A	about 920 W	not found on dealer sheets	not stated
1/2 HP, 230 V	5 A (6 A service-factor max)	about 1,150 W (1,380 W)	32.2 A	about 7,400
1/2 HP, 115 V	12 A service-factor max	about 1,380 W	64.4 A	about 7,400
3/4 HP, 230 V	6.8 A	about 1,560 W	not found on dealer sheets	not stated
1 HP, 230 V	8.2 A (10.4 A max)	about 1,210 W per sheet (1,600 W)	48.7 A	about 11,200

Figures are Franklin Electric’s, read from dealer specification sheets that reproduce them on September 11, 2026; Franklin’s own manuals are published as image PDFs. Where a dealer sheet did not carry the locked-rotor figure, the table says so rather than estimating one. Watts are amps times volts, which is volt-amps strictly, and the figure an inverter has to supply.

Two things stand out. The 115 V and 230 V versions of the 1/2 HP motor start at the same 7,400 VA, because the 115 V motor draws twice the amps at half the volts; changing the voltage does not change the problem. And the locked-rotor figure is about six times the full-load figure, the capacitor-start signature that the running versus surge watts guide explains and that submersible sump pumps mostly do not share.

Duty cycle: water, not the pump

Once running, a well pump is a modest load, and how much energy it uses in a day depends on how much water the house draws. USGS puts indoor use at roughly 80 to 100 gallons per person per day. A four-person household at 90 gallons is about 360 gallons; a typical residential submersible pump delivers around 10 gallons a minute at household pressure, so that is about 36 minutes of pumping in a day, a duty cycle of about 2.5%. Irrigation, livestock, a pool or a leaking toilet can multiply it.

Household	Gallons a day	Pump minutes at 10 gpm	Duty cycle	Daily Wh at 1,150 W
Two people, indoor only	about 180	18	1.3%	about 350 Wh
Four people, indoor only	about 360	36	2.5%	about 690 Wh
Four people plus a garden	about 700	70	4.9%	about 1,340 Wh
Heavy use: livestock or irrigation	about 1,400	140	9.7%	about 2,700 Wh

The well pump page runs its table at a 10% duty cycle, deliberately at the heavy end, because a battery sized for the heavy row is safe for every row above it and because outages are when everyone fills the bathtub. Your own figure is on the water bill or the meter.

What it means for the backup source

The daily watt-hours are small; a 2 kWh usable battery covers most households’ water for a day. The start is the problem. A source has to deliver 240 V (for the common 230 V motor) and survive a 7,400 VA start, which rules out every 120 V portable unit and most 240 V ones; the expandable roundup shows which single units state a surge figure above it, and the battery versus generator page covers the generator’s sizing rule, 7,500 starting watts or more with a 240 V outlet. Installed home batteries quote a 185 A start capability, which is why they run a well pump without comment.

Reading your own motor

The control box or the pump’s paperwork lists the motor model; Franklin’s model numbers encode horsepower and voltage. If the plate lists a service-factor amps figure and a locked-rotor figure, use those; they are the numbers above, for your motor rather than the table’s. And a well pump is hardwired at 240 V, so any backup connects through a transfer switch a licensed electrician installs, which is the transfer switch guide’s subject and not this page’s.