How this is calculated
Runtime is your daily water volume divided by the pump’s flow rate — a 200-gallon household day through a 10 GPM pump is just 20 minutes of pumping. Energy per day is running watts × that runtime. At the defaults it lands around 500 Wh: less than a mini fridge. Well pumps are a power problem, not an energy problem.
The power problem is the start. An across-the-line submersible kicks at roughly 3× running watts — 4,500W for a ¾ HP pump — and your inverter has to clear that peak with everything else still running. That single number disqualifies most small inverters. A soft-start or VFD pump controller (~1.5×) is the cheapest fix in off-grid water; the pressure tank matters too, since a bigger tank means fewer starts.
Voltage is the other gate: most pumps ¾ HP and up are 240V, which needs split-phase output — either an installed inverter that does 120/240V or a split-phase-capable station pair. The split-phase guide covers exactly this.
- Pump to a storage tank during solar hours and gravity-feed or re-pressurize from there — it converts a brutal surge load into a gentle daytime one.
- A larger pressure tank cuts starts per day — and starts, not runtime, are what stress an off-grid system.
- Dedicated solar well pumps (slow, DC, no surge) fill a tank all day on a couple of panels — the classic ranch solution.
Choosing between well, spring and rain? Read choosing your off-grid water source, then size storage with the water calculator.
Quick answers
How many watts does a well pump use?
About 1,000W at ½ HP, 2,000W at 1 HP, 3,200W at 2 HP while running — with a ~3× start-up surge on standard motors.
How much energy per day?
Typically 300–600 Wh — 20-odd minutes of actual pumping supplies a whole household day.
Can a power station run one?
A ½ HP 120V pump with soft-start, yes. Anything 240V needs split-phase capability — an installed inverter or a stacked pair rated past the surge.