Solar for swimming pools

A single-speed pool pump draws about 1–2 kW whenever it runs. Run it eight hours a day and that is 8–16 kWh, run it twelve and it is up to 24 kWh — compared with 1–2 kWh a day for a refrigerator. Across a five-month Colorado season, a single-speed pump on a typical schedule uses roughly 1,500–3,000 kWh, which for many households is more than a quarter of their annual electric use crammed into the sunniest months.

That timing is the good news. Colorado’s solar production peaks from May through August, when the pump runs longest. A system sized with the pool in mind produces the pump’s energy in the same weeks it is consumed, and net metering under C.R.S. 40-2-124 in Xcel and Black Hills territory credits any surplus for later. In co-op or municipal territory, check the annual true-up rules before counting on carryover.

The cheapest pool energy is the energy you never use. A variable-speed pump running at low speed for more hours moves the same water through the filter using a fraction of the electricity, because pump power falls steeply as speed drops. Owners who switch from a single-speed pump commonly see the pump’s share of the bill fall by more than half; the exact figure depends on plumbing, filter, and how long the old pump ran.

For solar sizing, that matters: a pool on a variable-speed pump may only need 2–4 extra panels rather than 6–8. We ask what pump you have before quoting, and if it is a single-speed unit, we suggest replacing it first. It is not our trade, but it changes our numbers, and it usually pays back faster than any panel.

Solar thermal pool heating runs pool water through unglazed black polymer collectors on the roof and back to the pool, using the existing pump. It is efficient in the sense that it converts sunlight to warm water directly, and it can extend a Front Range swimming season by several weeks on each end. We do not install it. Colorado freezes require the collectors to drain fully every fall and the plumbing to be designed for it, and roof penetrations for water lines are a leak risk that a pool contractor, not a solar electrician, should own.

The alternative on the electric side is a heat-pump pool heater, which draws roughly 3–6 kW and delivers several times that in heat. Paired with PV, it can hold a pool in the high 70s through summer and stretch the season on either end, at a cost in panels rather than plumbing. The constraint is the season itself: most Colorado pools are open four to five months, and no heater makes an outdoor pool cheap to run in October at 5,000 feet. Gas heaters remain common and solar does nothing for them.

If you are choosing between the two for a new pool, the honest split is: thermal collectors when the roof has a large unshaded south-facing area you are willing to give up and a pool contractor who will service the plumbing; a heat-pump heater on PV when you want one system, one trade, and electricity that also runs the rest of the house.

Since November 2025, Xcel’s residential time-of-use plan prices weekday electricity from 5 to 9 pm at roughly 2.7 times the off-peak rate, and summer months carry their own higher pricing. A pool pump scheduled to run midday, when your panels are producing, costs almost nothing; the same pump running at 6 pm draws on-peak grid power at the highest rate of the year. Set the timer for roughly 9 am to 4 pm and the problem largely goes away.

That schedule also means a pool does not justify a battery on its own. The pump is a daytime load by choice, so there is little evening consumption to shift. A battery still makes sense for other reasons — backup, or covering AC and cooking in the 5–9 pm window — but do not buy one for the pool.

Take the pump’s seasonal use — say 1,500–3,000 kWh for a single-speed pump, roughly half that for a variable-speed unit — and add a heat-pump heater’s use if you have one, which can be another 1,500–3,000 kWh over a season depending on the target temperature and whether you cover the pool at night. A well-placed Colorado kilowatt of panels yields roughly 1,300–1,600 kWh a year, so a pool typically adds 1.5–3 kW to a system, or about 4–8 panels at 400–440 W each, and closer to 10 with an aggressively heated pool.

At our $2.80–$3.25 per watt residential pricing, the pool’s share of an array runs roughly $4,000–$10,000 before any incentives. As of September 2026 there is no federal homeowner credit, so we show cash, RENU loan, and lease or PPA options side by side and let the numbers speak. A pool cover is the cheapest upgrade of all: it cuts evaporative heat loss dramatically and shortens how long any heater runs.