Off-grid, RV & cabin
Enter your household size, well depth, and pump wattage. Get both the solar panel size and the inverter size your pump needs.
How it works The real comparison is against a grid connection. The 25-year lifetime savings calculator in our Savings & Payback section can help you weigh the system cost against what the grid would charge.
Step 1
Occupant count and gallons per person set your total daily demand.
Step 2
Total head determines daily pumping energy, while pump wattage sets inverter surge sizing.
Step 3
These two numbers can differ dramatically for a well pump, and both matter.
For a household of 4 using 50 gallons per person a day, pumped from 120 feet of well depth plus 15 feet of additional lift, only about 51 watts of solar covers the daily pumping energy. The inverter, however, needs roughly 2,250 watts to handle the pump's starting surge, a striking difference between the two sizing figures. Once you have that number, the annual maintenance cost estimator shows what it means for the rest of the system.
Daily pumping energy is genuinely small since the pump only runs a few minutes total per day even for a full household's water use, but the inverter must be sized for the pump motor's starting surge, commonly 2 to 3 times its running wattage, which is a much larger instantaneous power draw than the daily average suggests. Sizing the inverter off daily energy alone would leave the pump unable to start at all.
A common planning figure is around 50 gallons per person per day for typical household use including showers, dishes, and laundry, though water-efficient fixtures and conservation habits can bring this down meaningfully for cabins where water use is deliberately minimized. Adjust this figure based on your household's actual habits and fixture efficiency rather than assuming a single number fits every situation. Well output varies a lot by region, and USGS's water resources data is a reasonable starting point for understanding regional groundwater conditions.
A standard pressure tank stores a buffer of pressurized water so the pump cycles on periodically to refill the tank rather than running continuously every time a faucet opens, which meaningfully reduces both pump cycling frequency and total daily runtime. This is why the actual daily pumping energy is so much lower than a naive calculation assuming continuous pump operation would suggest. EPA's guide to protecting a private well covers the maintenance side of keeping a pump system like this running reliably over the years.
Check the off grid water pump load calculator for a more detailed cycle-based load breakdown, and see the emergency backup minimum sizing tool if your well pump is part of a broader emergency backup plan. For the electrical side specifically, the inverter sizing for well pump startup in our inverters and equipment tools goes deeper into the surge-current problem, and the annual maintenance cost estimator in our maintenance and lifespan tools helps budget for ongoing upkeep.
Questions
For a household of 4 using 50 gallons per person a day, pumped from 120 feet of well depth plus 15 feet of additional lift, only about 51 watts of solar covers the daily pumping energy. The inverter, however, needs roughly 2,250 watts to handle the pump's starting surge.
Daily pumping energy is genuinely small since the pump only runs a few minutes total per day, but the inverter must be sized for the pump motor's starting surge, commonly 2 to 3 times its running wattage, which is a much larger instantaneous power draw than the daily average suggests.
A common planning figure is around 50 gallons per person per day for typical household use including showers, dishes, and laundry, though water-efficient fixtures and conservation habits can bring this down meaningfully for cabins where water use is deliberately minimized.
Yes, significantly. A standard pressure tank stores a buffer of pressurized water so the pump cycles on periodically to refill the tank rather than running continuously every time a faucet opens, which meaningfully reduces both pump cycling frequency and total daily runtime.
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