What size generator to run a well pump (1/2 hp)?
Well pump (1/2 HP) sizing at a glance: it draws 1000 running watts, surging to 3000W at startup.
| Spec | Value |
|---|---|
| Running watts | 1000W |
| Starting (surge) watts | 3000W |
| Recommended class (this load + margin) | 4000W |
Why the startup surge matters
Because a well pump (1/2 hp) has a motor, it surges to about 3000W at startup — roughly 3× its running draw. If you size a generator only for the running watts, it can stall the instant the well pump (1/2 hp) switches on. Always size for the surge.
Sizing the whole system
The number above covers the well pump (1/2 hp) on its own with a safety margin. In a real outage you'll run other things too — and the right method is your total running load plus the single largest surge among everything, not the sum of every surge. Use the full calculator to size your actual setup:
Common questions
How many watts does a well pump (1/2 hp) use?
A typical well pump (1/2 hp) draws about 1000 running watts, but needs roughly 3000 watts at startup due to motor surge.
What size generator runs a well pump (1/2 hp)?
For the well pump (1/2 hp) alone plus a safety margin, a 4000W (≈4.0kW) class generator is appropriate. Add your other essential loads to size the full system.