Home solar in rural America: how much battery do you need to run a well pump?

There’s no shortage of advice on how to size a home solar system, but most of it assumes a suburban house with city water and a long list of optional loads. Rural homes play by different rules, and when your water comes from a well, keeping the lights on is optional — but keeping the well’s pump running isn’t.

Here’s what it really takes, in solar and battery terms, to keep your home’s water flowing even when its electrons aren’t.

Rooftop solar has become common enough on upscale suburban homes and commercial buildings, but it’s still surprisingly rare in rural America. What’s more, many Americans (rural or otherwise) don’t realize that solar panels alone can’t power a home when the grid is down. For that, you need a home battery system to store the DC energy generated by the panels and convert it into usable AC power for your appliances.

I say “surprisingly” because when outages hit, rural areas are often the last to see power restored — making farm and horse-country households ideal candidates for solar-plus-battery backup.

As clever as that observation is, the inspiration for this post wasn’t my own cleverness. Instead, it came from one of my favorite story sources: the Electrek comments.

Please include data on capability to power well pumps. Those of us in rural areas can do without many electrical appliances during a power outage, but not having water is a major issue. Assume 20 amp, 220V for the circuit.

Jb

I thought it was a fantastic question – but how to answer it? Instead of running off to ChatGPT or Perplexity and hoping for the best, I decided to follow my own advice and ask the experts. In this case, that meant reaching out to my good friend, Emily Walker. Emily (who received a Masters’ in Environmental Science and Policy from Johns Hopkins University) is not just smart, she works with data from home- and commercial-grade solar installations all day in her role as Director of Insights at Energy Sage, so seemed uniquely equipped to give me a solid answer.

I sent her Jb’s comment word-for-word, and this is the response I got back:

220V * 20A = 4,400 watts (4.4 kW)

So, the inverter and battery system must be able to handle a continuous power output of at least 4.4 kW.

Most well pumps have startup surges that are significantly higher than the running power draw. Let’s assume it’s 2X.

4.4 kW * 2 = 8.8 kW

So, the inverter and battery system must be able to handle a peak power output of at least 8.8 kW.

Well pumps typically run intermittently, not continuously. Let’s assume the daily runtime is about 2 hours total per day.

4.4 kW * 2 hours = 8.8 kWh/day

So, the battery system must provide at least 8.8 kWh of usable battery storage to comfortably run the well pump for a day during an outage. For reference, the Tesla Powerwall 3 provides 11.5 kW of peak power output and 13.5 kWh of usable storage capacity. It could power a well pump during an outage.

EMILY WALKER

Since the comment came from a post titled “It’s time to start recommending some Tesla Powerwall alternatives,” I feel somewhat obligated to add that the modular Enphase IQ Battery 10T or Generac PWRcell units, with 9-10 kWh capacity and ~3.5-5 kW of power output, are also up to the challenge, though a single battery unit may struggle with the pump’s startup surge and household energy needs making a two battery system the go-to. For a single battery solution, the FranklinWH aPower almost exactly matches the Powerwall with 13.6 kWh capacity and up to 10 kW of peak output (5 continuous).

The good news if your budget forces you to go for one of the smaller battery options is that (as Emily points out) well pumps don’t need to run constantly, or for very long, to effectively provide you with needed water during a prolonged outage – and a little planning can go a long way toward stretching a limited battery capacity.

During an outage, run the well pump intentionally, turning it on 20–30 minutes before you plan to shower, do dishes, or flush toilets, then shut it back off once you’re done.

If you have some advance warning that severe weather or a even a planned outage is coming, pre-fill bathtubs, sinks, and other spare containers so you’re relying less on the pump when the batteries are under stress. Managing when, not just how the pump runs can easily double how long even a modest home battery system keeps water flowing.

And, finally, it’s always smart to get multiple independent quotes and talk to your trusted financial experts before moving forward with any major home improvement project.

Original content from Electrek.

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