Last updated: 5 September 2026 · Private residential pools in France — climate zones H1–H3

What size heat pump does your pool need?

Who this is for: this calculator sizes the heat pump for a private residential pool in France — in-ground or above-ground, up to 100 m³, heated over an April-to- September season. The H1/H2/H3 climate zones and the tariffs quoted are French. It does not cover public, hotel or municipal pools, whose sizing and regulations differ. If your pool is outside France, select your climate zone manually in step 3.

The rule French installers use fits on one line: the power in kW is roughly your pool's volume in m³ times a climate coefficient — about 0.18 in a cold zone (H1), 0.15 in a temperate one (H2) and 0.12 on the Mediterranean coast (H3). So a 50 m³ pool in a temperate climate needs around 7.5 kW, plus a margin of about 25 % for heating up: a range of 7.5 to 11.5 kW depending on the region.

That starting point is then corrected for whatever makes your pool lose or keep heat: an uncovered pool needs about 30 % more, an enclosure up to 40 % less, and aiming for 28 °C instead of 26 °C adds 12 %. The calculator below applies every one of those factors from five questions and shows its working. The result is accurate to about ±15 % — the same spread you would get between two professional quotes.

Recommended power by pool volume

In-ground pool, covered most of the time, in the open air, water at 26 °C, standard April- to-September season. Each range runs from the bare minimum to the 25 % margin.

Without a cover, add about 30 % to these values. Under an enclosure, take 15 to 40 % off depending on the type. The calculator makes those adjustments for you.

How this calculator works

This calculator gives you an instant, personalised estimate of the power your pool's heat pump needs, with every step shown so you can check it yourself.

We start from how much water your pool holds, multiply it by a climate number for your region, then nudge that up or down for the things that make a pool lose or keep heat.

The answer is a power range rather than a single figure: any pump inside it will heat your pool well, and a bigger one simply heats it a little faster. Use it as a confident starting point to compare models and quotes — it complements, rather than replaces, an installer's on-site survey.

Two quick terms. kW is power — how fast the pump delivers heat, and the number this tool gives you. kWh is energy — power used over time, i.e. what shows up on your electricity bill.

The formula behind the result

Here is the exact calculation — nothing is hidden:

rawPower = volume
         × climateCoeff[zone]     // 0.18 / 0.15 / 0.12   ← the core
         × coverFactor[cover]     // is it covered?
         × enclosureFactor[abri]  // is it under a shelter?
         × typeFactor[poolType]   // in-ground or above-ground?
         × tempFactor[targetTemp] // how warm you want the water
         × windFactor[wind]       // how exposed it is
         × seasonFactor[season]   // summer / standard / year-round

power = max(3.5, rawPower)         // never below the smallest real pump

The square-bracket notation just means "pick the value for your case": climateCoeff[zone] is the climate number for your zone, coverFactor[cover] is the factor for your cover, and so on.

The core is the first line: volume × climateCoeff[zone]. This is the standard volume-based sizing method used by installers, and on its own it already lands within about 10–15 % of what an installer would quote [1][2]. A bigger pool, or a colder climate zone, means more power — nothing more complicated than that.

The adjustments are everything that follows. Each one is a simple multiplier: it equals 1.0 for a "typical" pool, sits above 1.0 when it raises the power needed, and below 1.0 when it lowers it.

They exist because no two pools lose heat the same way — a covered, sheltered pool in mild air behaves very differently from an exposed, uncovered one. By capturing the real heat drivers (cover, shelter, exposure, target temperature, pool type), the adjustments turn a generic estimate into one that fits your pool. That is what makes the recommended range tight and realistic instead of a one-size-fits-all guess.

Finally, max(3.5, …) simply means we never recommend a pump smaller than the smallest model that actually exists.

The factors, in plain language

• How much water (volume). More water means more to heat, so this is the starting point — that is why we ask for length, width and depth.
• Where you live (climate). Colder regions lose heat faster and need more power. You just enter your postal code and we convert it into France's official climate zone [3], so you never have to guess.
• A cover. The single biggest lever: evaporation is a pool's number-one source of heat loss, so a cover dramatically cuts the power you need.
• Shelter and wind. An enclosure (a pool shelter or "abri") traps heat and lowers the power needed; an exposed, windy spot speeds up evaporation and raises it — and a very exposed spot (seaside, plateau, open plain) raises it more.
• Your target temperature. Every extra degree costs power — that is why aiming for 28 °C needs more than a comfortable 26 °C.
• Your heating period (season). Heating only in summer means mild air and lower power; stretching the season into colder air needs more power and costs more to run (the pump also loses efficiency as the air cools). Year-round use in cold air assumes a pool enclosure — without one, a standard air/water pump can't keep up.

At a glance: what raises or lowers your power

Starting from a "typical" pool (covered most of the time, in-ground, open air, 26 °C), each choice moves the power up or down:

These percentages are our own calibrated estimates (see the references note at the end); each is "no change" for the typical pool above.

A worked example you can try

Choose the "8 × 4 m" standard pool preset (an 8 × 4 × 1.5 m in-ground pool, which holds 48 m³ of water). Enter postal code 33000 (Bordeaux — climate zone H2), leave the cover on "at night", and set the target temperature to 28 °C.

Dropped into the formula, that gives:

rawPower = 48 (m³) × 0.15 (H2) × 1.15 (cover at night) × 1.0 (no shelter)
                   × 1.0 (in-ground) × 1.12 (28 °C) × 1.0 (moderate wind)
                   × 1.0 (standard season)
         ≈ 9.27 kW   →   recommended range 9.5 – 11.5 kW

How does 9.27 kW become a 9.5 – 11.5 kW range? We round the target to the nearest half-kilowatt (→ 9.5 kW, the sensible minimum), then add up to +25 % headroom (→ 11.5 kW) so the pump still heats comfortably in cooler weather. Any pump inside that band suits this pool; a bigger one just warms the water faster.

Here the climate coefficient 0.15 is our calibrated value for temperate zone H2; it is consistent with the published per-region power charts [2] once you account for our covered-pool baseline (see the honesty note below). The cover (1.15) and temperature (1.12) factors are likewise our own calibrated estimates.

Where our numbers come from

These are not made-up figures:

• The "volume × climate" method is the standard volume-based sizing method used by installers [1]. The specific coefficients (about 0.18 in cold zone H1, 0.15 in temperate H2, 0.12 on the Mediterranean H3) are our own calibrated values — no single guide publishes that exact set. They line up with independent per-region power charts [2] once you allow for the fact that our coefficients assume a covered pool (uncover it, and our 0.12 / 0.15 / 0.18 rise to about 0.16 / 0.20 / 0.23 kW/m³, within the published per-region range).
• The climate zones are France's official RT2012 zones, defined by Météo-France [3].
• The heat-up time relies on a basic physics constant: it takes 1.163 watt-hours to warm one litre of water by one degree [1].
• The running-cost estimate uses a typical electricity price [5] and a typical pump efficiency, or COP [4] — and you can adjust both in the advanced options. Your heating period also moves the bill: a longer season means more hours running and a lower average COP as the air cools, so a year-round setting costs noticeably more than a summer one. (Cost figures current as of June 2026, when the regulated base rate was about 0.19–0.20 €/kWh; set your own tariff for an exact bill.)

In all honesty: a few of the fine-tuning percentages (for example the exact effect of a cover, a shelter, wind exposure or the heating-period setting) are our own calibrated estimates, and we say so openly. Overall the result is accurate to about ±15 % — the same spread you would get between two professional quotes. That is exactly why we give you a range and not a single "perfect" number.

We test it. The model is locked by an automated check against independent reference cases. For example, for an 80 m³ pool near Rennes our recommended 17 – 21.5 kW band brackets an independent professional configurator's 17.4 kW; small cold-climate and covered Mediterranean pools pass the same check, each landing within the tool's ±15 % accuracy. If a coefficient ever changed, that test would flag it.

Independent by design: the power is worked out first, purely from your pool's characteristics. Any product suggestions are matched to that result afterwards — the sizing is never influenced by what is for sale.

When to double-check with a professional

This calculator is a reliable starting point for a typical outdoor home pool. Ask an installer for a tailored quote when:

• your pool is indoor — a very different heat-loss profile (the tool flags this result as indicative);
• you want to heat year-round in cold air — a standard air/water pump drops out below about 5 °C, so this case really needs a pool enclosure (the tool flags it);
• it is very large or an unusual shape — the model assumes a roughly rectangular pool;
• it sits in an extreme spot — high altitude, very exposed, or a strong local micro-climate that a department-level climate zone cannot capture.

In those cases, use the range as a sanity check rather than the final word.

Beware the power printed on the box

The power you just calculated is useful power, at the 15 °C air / 26 °C water reference condition. Manufacturers, however, usually advertise the figure measured at 26 or 28 °C air — far more favourable conditions. Across the models we analysed the gap commonly reaches 25 to 35 %: a pump sold as "9 kW" may deliver only 6.4 when you actually need it.

So before you buy, read the spec sheet at the same air temperature the sizing was done at.

Common questions