How Much Does It Cost to Heat a Home Swimming Pool?
The honest answer is: it depends — but it can be estimated, and the estimate is usually more useful than a single headline figure. The running cost of heating a home pool comes down to two things: how much heat the pool needs, and how efficiently your heat pump supplies it. Once those are clear, the arithmetic is straightforward, and the same few factors explain why one pool costs a little to heat and another costs a lot.
This article breaks the cost into its parts, gives a simple way to estimate your own, and points out the levers that make the biggest difference. It is a companion to our guide on [how to choose the right pool heat pump](/https://nordthermglobal.com/blog/how-to-choose-the-right-pool-heat-pump-for-a-home-swimming-pool); here the focus is purely on running cost.
The Short Answer
The one-off cost to **heat the water up** can be calculated directly from pool volume, temperature rise, heat-pump COP and electricity price. In the worked example below, heating a 40 m³ pool from 20 °C to 28 °C requires about **74 kWh of electricity at a COP of 5**; multiply that by your local tariff to estimate the cost. The ongoing **seasonal cost of holding** that temperature varies much more because it depends on local weather, exposure and whether the pool is covered. Estimating that part reliably requires local climate and pool heat-loss data.
Two Different Costs: Heating Up vs Holding Temperature
It helps to separate two things that are often lumped together.
The first is the **initial heat-up** — raising the pool from its current temperature to your target the first time, or after a cold spell. This is a one-off energy cost each time you do it, and it is easy to estimate because it depends almost entirely on water volume and the temperature rise.
The second is **maintaining temperature** — replacing the heat the pool loses day after day. Over a full season this is usually the larger part of the bill, and it is harder to pin down because it depends on surface area, climate, wind and, above all, whether the pool is covered. Most people underestimate this ongoing cost and overestimate the heat-up cost.
Estimating the Initial Heat-up Cost
Raising the temperature of water takes a predictable amount of energy. As a working formula:
> **Quick formula** — Electricity (kWh) ≈ Pool volume (m³) × Temperature rise (°C) × 1.163 ÷ COP
The 1.163 is the energy (in kWh) needed to raise one cubic metre of water by one degree; COP is your heat pump's coefficient of performance under the conditions you are heating in.
A worked example, with every assumption stated so you can swap in your own:
- Pool volume: **40 m³**
- Temperature rise: **8 °C** (say 20 °C up to 28 °C)
- Assumed COP: **5** (illustrative — your real figure depends on air and water temperature)
- Assumed electricity price: **0.30 per kWh** (use your local tariff)
Energy delivered to the water ≈ 40 × 8 × 1.163 = **372 kWh (thermal)**. At a COP of 5, the electricity used ≈ 372 ÷ 5 = **~74 kWh**, or about **22 units of local currency** at the price above. That is the one-time cost to heat the pool up. To see how much the inputs matter: if your electricity price doubles, this cost roughly doubles; and if the seasonal COP drops from 5 to 3.5 in colder weather, the electricity used rises by around 40% for the same heat. The formula itself matters far less than these two numbers.
This is a useful planning estimate, not a meter-level prediction. Actual consumption can also include circulation-pump electricity, pipe and equipment losses, defrost operation and changes in COP as air and water temperatures change.
## What It Costs to Hold Temperature
Once a pool is warm, the heat pump only has to replace what the pool loses. For an outdoor pool, most of that loss happens at the water surface — mainly through evaporation, then radiation and convection — which is why surface area and exposure matter more here than volume.
There is no clean single formula for this, because it varies with your climate, wind exposure, how many degrees above ambient you hold the water, and how long your season runs. Over a season, maintenance can add up to more than the initial heat-up, particularly for an uncovered pool in a windy or cool location. A realistic estimate for a specific pool is best done with local climate data or a supplier sizing check rather than a generic number — but the levers below are what actually move it.
## The Three Biggest Levers on Cost
**1. A pool cover.** This is usually the single most effective way to cut running cost. Because most heat leaves an outdoor pool at the surface, a cover sharply reduces evaporation and overnight loss, which directly lowers how hard and how long the heat pump has to run — without a cover, evaporation quietly carries heat away from any pool, however good the unit. A cost estimate for an uncovered pool and the same pool covered can differ substantially. This [Australian residential pool heat pump installation](https://nordthermglobal.com/case/residential-pool-heat-pump-installation-for-an-existing-swimming-pool-in-australia) shows a heat pump retrofitted to an existing pool and paired with a thermal cover.
**2. COP — and the conditions behind it.** Running cost is inversely related to seasonal COP: a higher COP means less electricity for the same heat. But COP is not a fixed number. It is measured under stated conditions, and it falls as the air gets colder or the temperature lift increases. This is why heating in cool shoulder-season weather costs more per degree than topping up on a warm summer day, and why comparing units on headline COP alone — without their test conditions — can be misleading.
**3. Target temperature and season length.** Every extra degree you hold above the natural water temperature adds ongoing load, and a longer season means more days of maintenance. Holding a pool at 30 °C from early spring is a very different bill from 27 °C across peak summer only.
Heat Pump vs Other Ways of Heating a Pool
Cost differences between heater types come down to efficiency. An electric resistance heater turns roughly one unit of electricity into one unit of heat. A heat pump does not create heat directly — it transfers heat from the surrounding air into the pool water — so with a seasonal COP of, say, four to five it delivers four to five units of heat per unit of electricity, meaning its running cost is generally a fraction, often around a fifth to a quarter, of resistance heating for the same delivered heat.
Against gas, the comparison depends on local gas and electricity prices and burner efficiency, so it varies by market; in many regions a heat pump still comes out lower on running cost, but it is worth checking against your own energy prices rather than assuming.
Inverter vs On/Off and Running Cost
The control type also affects the seasonal bill. An inverter unit can modulate down and run at a lower output once the pool is near target, which is often more efficient over a season than a fixed-output unit cycling on and off. The benefit is greatest when the unit is correctly sized and spends substantial time operating at partial load; the actual saving still depends on climate, sizing, water flow, control logic and how the pool is used. This trade-off is covered in a dedicated comparison.
Estimating Your Own Cost: A Quick Method
To get a figure for your pool:
- ✓ **Initial heat-up:** volume (m³) × temperature rise (°C) × 1.163 ÷ COP × your electricity price
- ✓ **Set a realistic COP** for your conditions, not the headline number
- ✓ **Assume a cover** if you want the lower, more representative running cost
- ✓ **Decide your target temperature and season length** — these drive the ongoing part
- ✓ **For the maintenance figure**, use local climate data or a supplier sizing estimate rather than a generic average
FAQ
**Is it expensive to heat a pool?**
Compared with electric resistance heating, generally no — a heat pump's efficiency means much lower running cost for the same heat. In absolute terms it depends on your pool size, climate, electricity price and whether you use a cover.
**Does it cost more to heat a pool every day?**
If the pool is used frequently, maintaining a moderate setpoint can be convenient and allows an inverter heat pump to operate at partial load. If the pool will not be used for several days, lowering the setpoint usually reduces total heat loss and energy consumption. The best operating schedule also depends on weather, off-peak tariffs and how quickly the heat pump can restore the target temperature.
**Should I leave the heat pump running all the time?**
For a pool used regularly, maintaining the target temperature — or using a small setback — can be practical. For longer periods of non-use, lowering the setpoint or switching to standby generally saves energy. Follow the manufacturer's freeze-protection guidance in cold weather.
**Can a pool cover really reduce heating costs?**
Yes, usually by a lot. Because evaporation is typically the single largest heat loss, a cover is generally the most cost-effective addition to a heated pool.
**Is a heat pump cheaper to run than an electric or gas heater?**
For the same delivered heat it is generally much cheaper than electric resistance heating, because it moves heat rather than generating it. Against gas it depends on local energy prices.
Conclusion
There is no single price tag for heating a home pool, but estimating it is straightforward once you know four things: your pool size, your target temperature, the COP you can realistically expect in your conditions, and your local electricity price. With those, most homeowners can reach a surprisingly accurate estimate before choosing a unit — and can see for themselves that a pool cover and a realistic COP move the number more than almost anything else.
Planning a residential pool project, or sourcing heat pumps for customers? Share your pool dimensions, target water temperature and location, and our team can help estimate the heating capacity you'll need and the running cost to expect before you settle on a unit. For choosing the unit itself, start with our guide on [how to choose the right pool heat pump](https://nordthermglobal.com/blog/how-to-choose-the-right-pool-heat-pump-for-a-home-swimming-pool). You can also compare Nordtherm's [R32 top-discharge residential pool heat pump](https://nordthermglobal.com/products/r32-top-discharge-pool-heat-pump-for-residential-swimming-pools) and [R290 full-inverter residential pool heat pump](https://nordthermglobal.com/products/r290-full-inverter-pool-heat-pump-for-residential-swimming-pools).
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*Nordtherm Global manufactures air-to-water and swimming pool heat pumps for distributors, installers and project buyers worldwide.*
