What a Pool Actually Costs to Run per Month, Line by Line

A typical residential in-ground pool runs $80 to $350 a month in season. The spread is almost entirely two lines: how the pump is run, and whether the pool is heated.

Typical US figures at around $0.15/kWh. Electricity prices vary two or three times across states, so scale accordingly.

The lines

Without a heater the pump dominates. With one, the heater does — and a gas heater on a large uncovered pool in cool weather can exceed everything else combined.

The pump is the line worth attacking

A single-speed 1.5 hp pump draws roughly 1,800–2,200 W. Running eight hours a day is around 15 kWh, or $2.25 a day at $0.15 — $67 a month.

A variable-speed pump running at half speed uses roughly one-eighth the power, because power scales with the cube of speed. It has to run longer to move the same water, so the net saving is typically 60–80%, not 87%.

That turns $67 a month into $15–$25. Over a five-month season it is $200–$260 a year, and variable-speed pumps cost $700–$1,400 installed — so the payback is three to six years on a seasonal pool and under two on a year-round one. Several states now mandate them on new installations for exactly this reason.

Run time is the other half. The rule of thumb is one full turnover a day, not the eight hours everyone quotes. Divide your volume by the pump's flow rate in gallons per hour and you usually get less time than you are currently running.

The heater, and the cover that halves it

Most heat loss from a pool is evaporation from the surface, not conduction through the walls. Which is why a cover is the single most effective heating measure available.

• Solar cover (bubble cover): cuts heat loss roughly 50–70%. Costs $100–$400. Pays back within one heated month on most pools.
• Liquid solar cover: a thin monolayer, roughly 15–30% reduction. Useful where a physical cover is impractical.
• Automatic cover: $8,000–$20,000, and it also solves safety and debris.

A gas heater raising a 20,000 gallon pool by 10 °F uses roughly 1.7 million BTU — around 17 therms, or $25–$35 at typical gas prices, before any losses. Losing that heat overnight and reheating daily is what makes uncovered heated pools expensive.

A heat pump costs 3–5× less per unit of heat than gas but only works above roughly 50 °F ambient and heats slowly. For maintaining temperature through a season it is much cheaper; for heating a pool up for the weekend, gas wins.

Chemicals

$25–$60 a month for a 20,000 gallon pool, and the spread depends more on method than on brand.

Liquid chlorine bought in bulk is the cheapest per ppm and adds nothing cumulative. Tablets cost more per ppm and add CYA, which eventually forces a partial drain — a cost that shows up as a water bill two years later.

A salt system converts salt to chlorine on site, and needs a higher CYA level than a chlorine pool. Cell replacement runs $400–$900 every 3–7 years, which works out close to liquid chlorine on cost — the real advantage is convenience and water feel, not money.

Water

Evaporation from an uncovered pool is roughly ¼ inch a day in warm weather. On a 16 × 32 pool that is about 320 gallons a day, or 9,600 a month.

A cover cuts it by more than half, which is a second saving on top of the heating one.

Backwashing a sand filter uses 200–500 gallons each time. Cartridge filters use none — they are hosed off — which is worth knowing in areas with water restrictions or metered supply.

The three changes worth making, in order

1. Solar cover — cheapest, biggest effect on both heat and water
2. Variable-speed pump — biggest effect on electricity, real payback
3. Right-sized run time — free, and most pools are over-running

Chemicals are the line everyone tries to cut first and the smallest of the three. Getting the dose right saves more than shopping around does, and getting the dose right starts with knowing the volume rather than the brochure figure.