Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Annual well pump electricity cost
$25
Estimated daily runtime
0.50
Annual energy use
157
Estimated motor startup surge
2,152
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How to use this
- 1Enter well pump size (HP).
- 2Enter pump flow rate (GPM).
- 3Enter household daily water use (gal).
- 4Enter motor efficiency (%).
- 5Enter electricity rate ($/kWh).
- 6Read your annual well pump electricity cost on the right — it updates as you type.
- 7Hit Share to keep the scenario or send it to someone.
About this calculator
Estimates annual electricity cost for a residential well pump using motor horsepower, daily water usage, and pump flow rate to derive actual runtime, rather than assuming a flat number of hours. Well pumps are intermittent loads — they cycle on when the pressure tank drops below its cut-in setting and off at cut-out — so daily runtime depends on household water demand divided by the pump's flow rate (gallons per minute), not a fixed schedule. This also matters for the battery-backup and generator-sizing decisions, since well pumps are usually the highest-surge-load, most critical circuit to keep powered during an outage for households on a private well.
Worked example
Using the values the calculator loads with:
Inputs
- Well pump size: 0.75 HP
- Pump flow rate: 10 GPM
- Household daily water use: 300 gal
- Motor efficiency: 65 %
- Electricity rate: 0.16 $/kWh
Results
- Annual well pump electricity cost: $25
- Estimated daily runtime: 0.5
- Annual energy use: 157
- Estimated motor startup surge: 2,152
What each field means
Inputs
- Well pump size (HP)
- The well pump size used in the calculation, measured in HP. Starts at 0.75 HP so you have a working example on load. Accepted range: 0.25–3 HP.
- Pump flow rate (GPM)
- The pump flow rate used in the calculation, measured in GPM. Starts at 10 GPM so you have a working example on load. Accepted range: 2–30 GPM.
- Household daily water use (gal)
- The household daily water use used in the calculation, measured in gal. Starts at 300 gal so you have a working example on load.
- Motor efficiency (%)
- The motor efficiency used in the calculation, measured in %. Starts at 65 % so you have a working example on load. Accepted range: 40–90 %.
- Electricity rate ($/kWh)
- The electricity rate used in the calculation, measured in $/kWh. Starts at 0.16 $/kWh so you have a working example on load. Accepted range: 0.02–0.6 $/kWh.
Results
- Annual well pump electricity cost
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Estimated daily runtime
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Annual energy use
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Estimated motor startup surge
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Why does a well pump matter so much for backup power?
No pump means no water at all — not just for drinking, but for flushing toilets and fighting fires if you're on well water. It's also one of the highest-surge loads in a house (2.5-3x running watts at startup), which is why it's the first thing to check against a generator's or battery's surge rating during outage planning.
How do I find my pump's GPM and HP?
Both are usually on the pump's nameplate, often stamped on the motor housing itself or in the well completion report from when the well was drilled. If you can't access it, a well contractor can measure flow rate directly, and typical residential submersible pumps run 0.5-1.5 HP with 8-15 GPM.
Why is well pump motor efficiency lower than other appliances?
Submersible well pump motors are optimized for reliability in a sealed, water-cooled environment rather than peak efficiency, and older pumps especially can run 50-65% wire-to-water efficiency. A newer, correctly-sized pump can improve this meaningfully and also reduce the well's short-cycling if the pressure tank is properly sized.
Does a bigger pressure tank reduce energy cost?
Indirectly — a larger pressure tank means longer run cycles and fewer starts per day, which reduces motor wear and the energy penalty of frequent startup surges, though it doesn't change total daily runtime much since that's driven by total water used, not cycle frequency.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Well Pump Energy Cost Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/well-pump-energy
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/well-pump-energy" target="_blank" rel="noopener">Well Pump Energy Cost Calculator — RevenueLab</a> (2026).</p>
Source: [Well Pump Energy Cost Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/well-pump-energy) (2026).