Solar Pool Pump Calculator

Size a solar-powered pool pump and array. Get required flow, pump wattage, panel size, and dollar savings versus your existing 120 V / 240 V pool pump.

Total dynamic head is typically 15–25 ft for a standard cartridge-filter pool — add 5 ft for sand/DE filters, 5 ft per 50 ft of horizontal pipe run, and 5 ft if the equipment pad sits uphill of the pool. Don't drop below 1.0 turnover/day if anyone swims in the pool.

Pump & array assumptions

Pump efficiency (55% default) converts hydraulic power into the electrical power the pump motor draws. Array derate (85% default) sizes the PV array above the pump's rated power to cover controller and wiring losses and less-than-ideal sun angles — a smaller percentage here means a bigger, more conservative array.

By · Energy analysts and engineers documenting every formula, source, and limitation behind our calculators.

Published Formula, sources & limitations

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HOW IT WORKS

How does the solar pool pump calculator work?

The calculator chains three physical relationships together — how fast your pool needs to turn over, how much power that flow requires against your plumbing's resistance, and how big a solar array it takes to deliver that power reliably.

1

Enter your pool & plumbing

Pool volume, total dynamic head, and how many turnovers per day you need.

2

Set your sun window

How many hours the solar pump will run, and your location's peak sun hours.

3

Compare to your grid pump

Enter your existing pump's wattage, run time, and rate to see the array size and savings.

The formula

THE CALCULATIONFlow (GPM) = (pool gallons × turnovers/day) ÷ (solar run hours × 60)

Pump power (W) = (GPM × head ÷ 3,960) × 746 ÷ pump efficiency. Array (W) = pump power ÷ array derate. Daily energy (kWh) = array (kW) × peak sun hours. Annual savings = daily energy × 365 × electricity rate.

Worked example: a standard 20,000-gallon pool

EXAMPLE 1

20,000 gallons, 20 ft head, 1.0 turnover/day, 6-hour sun window, 4.8 peak sun hours, $0.16/kWh

  1. Required flow: (20,000 × 1.0) ÷ (6 × 60) ≈ 55.6 GPM.
  2. Pump power: (55.6 × 20 ÷ 3,960) × 746 ÷ 0.55 ≈ 381 W.
  3. Array size: 381 ÷ 0.85 ≈ 448 W.
  4. Daily energy: 0.448 kW × 4.8 h ≈ 2.15 kWh.
  5. Annual savings: 2.15 kWh × 365 × $0.16 ≈ $126.

Result: about 381 W recommended pump power, a 448 W array, and roughly $126 a year in displaced grid energy — a $2,200 kit pays back in about 17.5 years at this rate.

Worked example: a larger pool in a high-rate, sunny state

EXAMPLE 2

25,000 gallons, 25 ft head, 1.5 turnovers/day, 6-hour sun window, 6.5 peak sun hours, $0.32/kWh

Same formula, but a bigger pool with heavier use, a longer plumbing run (higher head), a sunnier location, and a much higher electricity rate — the combination common in parts of California and Arizona.

  1. Required flow: (25,000 × 1.5) ÷ (6 × 60) ≈ 104.2 GPM.
  2. Pump power: (104.2 × 25 ÷ 3,960) × 746 ÷ 0.55 ≈ 892 W.
  3. Array size: 892 ÷ 0.85 ≈ 1,049 W.
  4. Daily energy: 1.049 kW × 6.5 h ≈ 6.82 kWh.
  5. Annual savings: 6.82 kWh × 365 × $0.32 ≈ $797.

Result: about a 1,049 W array producing roughly $797 a year in displaced grid energy — at a $2,600 installed cost, payback lands around 3.3 years, far faster than Example 1 simply because of the higher rate and better sun resource.

Why payback varies so much by state

The two worked examples above use identical formulas but land on payback periods nearly six times apart — 17.5 years versus 3.3 years — almost entirely because of electricity rate and sun hours. The U.S. 2026 residential average rate is roughly $0.16/kWh, but California runs closer to $0.32 and Hawaii to $0.42; pair a high rate with a sunny climate like Phoenix (6.5 peak sun hours) and a solar pool pump can pay for itself in three to five years. In a low-rate, cloudier state, the same system can take well over 15 years — still worth it for the resilience of a grid-independent pump, but a much weaker pure financial case.

Common sizing mistakes

Underestimating head

Skipping the extra 5 ft for a sand/DE filter or a long pipe run undersizes the pump, so it can't hit its rated flow.

Copying the old pump's horsepower

Grid pumps run 24/7 at lower flow; solar pumps run fewer hours at higher flow. Size from turnover and run hours, not the old nameplate.

Skipping the array derate

Sizing the array to exactly match the pump's rated power leaves no headroom for controller losses or off-peak sun angles.

Ignoring turnover for actively swum pools

Dropping below 1.0 turnover/day to save on array size risks cloudy, algae-prone water if people are swimming regularly.

Privacy and appropriate use

Your inputs are processed directly in your browser and are not sent to a database. This is a planning-stage sizing estimate, not an engineering or installation document — a licensed pool or solar professional should verify your plumbing's actual head, local code requirements, and final equipment selection before you buy.

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FREQUENTLY ASKED QUESTIONS

Questions about the solar pool pump calculator.

Clear answers about flow rate, head, pump efficiency, and what counts as savings.

Why does the solar pump need more flow than a grid pump running all day?

A grid pump can spread its daily filtration job across 24 hours, so it can run at a lower flow rate. A solar pump only runs during your sun window — 6 hours is the standard residential target — so it has to move the same daily turnover volume in far less time, which means a higher flow rate and a bigger motor. That's why this calculator asks for "solar pump run hours" separately from your existing pump's run hours.

How is pump power calculated from flow rate and head?

This calculator uses the standard hydraulic power formula: water horsepower equals flow rate (GPM) times total dynamic head (ft), divided by 3,960. Converting to watts and dividing by the pump's wire-to-water efficiency (55% is a typical default for a permanent-magnet DC solar pool pump) gives the electrical power the pump motor actually draws.

Why is the solar array bigger than the pump's rated power?

The array is deliberately oversized relative to the pump's power draw — by default, sized at power ÷ 85%. That headroom covers charge-controller and wiring losses, non-ideal panel angle through the day, and cloudy-moment dips, so the pump gets reliable full-speed operation through most of the sun window rather than stalling whenever a cloud passes or the sun isn't at its peak angle.

How is total dynamic head different from just pipe length?

Total dynamic head (TDH) is the total resistance the pump has to overcome — it includes vertical lift, filter pressure drop, and friction loss through pipes, valves, and fittings, not just physical pipe length. A standard cartridge-filter pool typically runs 15–25 ft of TDH; add roughly 5 ft for a sand or DE filter, another 5 ft per 50 ft of horizontal pipe run, and 5 ft if the equipment pad sits uphill of the pool. When in doubt, use the higher end of the range — undersizing TDH is the most common way to end up with a pump that can't hit its rated flow.

Does a solar pool pump need a battery?

Most residential solar pool pump systems are grid-free but battery-free — the pump only runs while the array is producing enough power, typically matching daylight hours, and sits idle at night. That's fine for filtration, since pools don't need round-the-clock circulation. A battery adds cost and complexity that's rarely justified unless you specifically need the pump to run outside daylight hours.

What counts toward "annual savings" in this calculator?

Annual savings values the solar array's estimated daily energy output at your entered electricity rate — in effect, what that energy would have cost if purchased from the grid. It's a measure of the array's output value, not a direct dollar-for-dollar comparison against your specific old pump's bill, since the solar pump may run different hours than your existing pump. The calculator shows your existing pump's estimated annual running cost separately so you can compare the two directly.

Is a DIY solar pool pump kit actually cheaper than a grid pump?

Typical 2026 DIY DC solar pool pump kits — a 400–600 W array, pump, and controller — run $1,800–$2,800 complete; professional installation with roof penetration adds roughly $700–$1,500 in labor. Payback depends heavily on your electricity rate and how many hours your existing pump runs: in high-rate states like California or Hawaii, payback can run well under 5 years, while in low-rate states it can stretch past 15–20 years. Run your own numbers above rather than relying on a rule of thumb.

Is my data stored?

No. All inputs and calculations run directly in your browser and are not sent to a server or saved in an account. General site usage may be measured through Google Analytics as described in our Privacy Policy.