Answer 5 questions, get the ideal heat pump power for your pool

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.

What heat-pump power does my pool need? As a rule of thumb, take your pool's volume in m³ and multiply by a climate coefficient (0.18 in cold zone H1, 0.15 in temperate H2, 0.12 on the Mediterranean H3), then adjust for cover, shelter, pool type, target temperature and wind. Those coefficients are our own calibrated values: they follow the same direction as professional per-region sizing charts [2] — the colder the zone, the more power — and while the exact numbers differ from any single chart, the full calculation lands in the same recommended power range (we check this against independent references; see Where our numbers come from). The calculator does all of this and shows a range rather than one value.

Should I oversize my pool heat pump? A margin of about +25 % above the target power is healthy: it speeds up the temperature rise and keeps performance up in cooler weather. That is why the result is shown as a range, from the bare minimum up to that margin.

Does a cover really change the power needed? Yes — it is the single biggest factor, because evaporation is a pool's number-one heat loss. The baseline already assumes a cover; without one, the power required rises noticeably.

1. Cash Piscines — Le guide ultime pour dimensionner votre pompe à chaleur de piscine (the field-standard volume-based sizing method, its aggravating factors for cover and wind, and the 1.163 Wh/L·°C water-heating constant — it uses a ΔT-based formula, not a per-zone coefficient table). https://www.cash-piscines.com/conseils/article/le-guide-ultime-pour-dimensionner-correctement-votre-pompe-a-chaleur-de-piscine
2. Aqua Jardin — Pompe à chaleur piscine 50 m³ : quelle puissance ? (independent recommended power by climate region, used to cross-check the coefficients). https://aqua-jardin.fr/comparatifs/pompe-chaleur-piscine-50m3/
3. Ministère de la Transition écologique — Répartition des départements par zone climatique (the official government classification of French departments into climate zones H1/H2/H3, defined by Météo-France for the RT2012/RE2020 regulations). https://www.ecologie.gouv.fr/sites/default/files/documents/La%20r%C3%A9partition%20des%20d%C3%A9partements%20par%20zone%20climatique.pdf Plain-language overview: Hellowatt — Zone climatique France : définition, carte et impact. https://www.hellowatt.fr/renovation/globale/zone-climatique
4. Guide-piscine.fr — Qu'est-ce que le COP d'une pompe à chaleur de piscine ? (a pool heat pump's coefficient of performance: should not be below ~3.5, typically around 4). https://www.guide-piscine.fr/pompe-a-chaleur/qu-est-ce-que-le-cop-d-une-pompe-a-chaleur-de-piscine-5457_A
5. Fournisseurs-Électricité / EDF Tarif Bleu — regulated electricity price per kWh (Base option), used as the default running-cost rate. https://www.fournisseurs-electricite.com/fournisseurs/edf/tarifs/base

Note on the coefficients and factors: the volume × climate method is field-standard [1], and our per-zone coefficients are consistent with published per-region power figures [2] once normalised for our covered-pool baseline. But the exact 0.18 / 0.15 / 0.12 triplet, and the fine-tuning cover, shelter, wind, per-degree temperature and heating-period (season) factors, are calibrated in-house estimates — no single public source prints those exact values. We present them as engineering estimates, which is why the tool's output is a range accurate to roughly ±15 % rather than a single guaranteed figure.