What Does Your Air Conditioner Really Cost? How to Measure Its Actual kWh Consumption
L'équipe Proclimo
16 Sep 2026 - 08 min read
"We had the air conditioning installed in June, and we got hit with an extra €180 on the September adjustment. Is that normal, doctor?" There's no answering that question without a number: the quantity of kilowatt-hours the unit actually consumed. And almost nobody has it. You know the cooling capacity written on the quote, you vaguely remember a letter on the energy label, and you discover the outcome three months later, buried in a single bill that lumps together the water heater, the induction hob and the EV charger.
The good news is that measuring the consumption of a reversible air conditioner is now within everyone's reach, for a few dozen euros or even for free. And the exercise often holds surprises — in both directions. This article explains why the manufacturer's figures aren't enough, how to obtain a reliable measurement, and which settings actually move the needle.
Why the manufacturer's figures don't answer your question
Three numbers appear systematically on the spec sheet of a wall-mounted split unit. They don't describe the same thing, and none of them translates directly into a bill.
Cooling (or heating) capacity, expressed in kW, is the amount of cold or heat delivered into the room. A "2.5 kW" unit doesn't consume 2.5 kW: it delivers 2.5. This is the most common confusion.
Power input, more discreetly noted in the documentation, is the actual electricity consumption at full load. For a split unit rated at 2.5 kW of cooling, it sits somewhere around 0.6 to 0.8 kW. That's the figure that turns into euros.
SEER and SCOP are seasonal efficiency ratings. SEER (Seasonal Energy Efficiency Ratio) measures cooling efficiency over a typical season, while SCOP (Seasonal Coefficient of Performance) does the same in heating mode. A SEER of 8 means that, on a seasonal average, the unit produces 8 kWh of cooling for every 1 kWh of electricity consumed.
| Indicator | What it measures | Typical 2026 values (wall-mounted split) |
|---|---|---|
| Cooling capacity | Cooling delivered | 2.0 to 5.0 kW |
| Power input | Electricity consumed | 0.5 to 1.6 kW |
| SEER | Seasonal cooling efficiency | 6.1 to 9.5 |
| SCOP | Seasonal heating efficiency | 4.0 to 5.2 |
The catch: SEER and SCOP are calculated under the European standard EN 14825, using a standardised climate profile (average climate, referred to as "Strasbourg" for heating) and an idealised part-load operation. Your home is not a laboratory. An outdoor unit facing due south on a dark gravel terrace, a poorly insulated room, open windows, a setpoint of 19 °C in the middle of August: all of this can push real-world efficiency 30 to 40 % below the label.
Hence the value of measuring rather than estimating.
Three ways to measure, from the simplest to the most precise
1. The Linky meter: free and underused
If your home has a Linky smart meter, you already have an hourly consumption history available on the Enedis customer portal. The principle: compare a day when the air conditioning ran with a comparable day without it, at equivalent season and occupancy.
The method has obvious limits — it measures the whole home — but it gives an honest order of magnitude if you go about it properly:
- enable the hourly load curve in your Enedis account (it isn't always recorded by default; you have to give your consent);
- pick one heatwave day and one mild day with the same presence at home;
- subtract the two daily totals.
The difference is, roughly speaking, your air conditioning. On a 34 °C day in a properly insulated two-bedroom flat, expect somewhere between 6 and 14 kWh.
2. The plug-in power meter: the tenant's solution
If your indoor unit or portable monobloc plugs into a standard socket — as is the case with mobile air conditioners and some plug-and-play splits — measurement becomes trivial. A plug-in electricity consumption meter sits between the socket and the appliance and totals up the kWh consumed. Models costing under twenty euros display instantaneous power, cumulative consumption and cost if you enter your price per kWh.
It's the most educational tool there is: you watch the unit climb to 900 W on start-up, then drop back to 250 W once the setpoint is reached. Plenty of people grasp how inverter technology works within two minutes in front of that display.
One caveat, though: this solution is not suitable for conventional split installations, whose outdoor unit is wired directly to a dedicated circuit from the consumer unit.
3. The DIN-rail energy meter: the reference measurement
For a fixed installation, the most reliable approach is to fit a modular energy meter on the DIN rail of the consumer unit, downstream of the breaker dedicated to the air conditioning. It totals the kWh on that circuit, exactly as the Enedis meter does for the whole home.
A single-phase 32 A model costs between €25 and €60. Some offer a pulse output or Modbus communication so the data can be fed to a home automation hub. Since working inside a consumer unit is no trivial matter, have it fitted during a servicing visit by your refrigeration technician or by an electrician: it's a fifteen-minute job.
An alternative with no work on the wiring: a connected clamp meter that clips around the live conductor of the air conditioning circuit. Accuracy is slightly lower (on the most basic models it estimates power without measuring phase shift), but installation is reversible and requires no power cut.
Turning kWh into euros: the full calculation
Once you have the kWh, converting to euros depends on your tariff. Under France's regulated electricity tariff, the flat-rate (Base) option sits around €0.20 to €0.21/kWh including tax in 2026, while the off-peak option drops well below that at night and, since the 2025-2026 reform of off-peak time slots, during an afternoon window in summer.
The formula is simple:
Cost = Average power input (kW) × Hours of operation × Price per kWh
Take a concrete case. A split unit rated at 3.5 kW of cooling, with a real average power input of 0.55 kW once the setpoint is reached, running 8 hours a day for 35 summer days:
- 0.55 × 8 = 4.4 kWh/day
- 4.4 × 35 = 154 kWh over the season
- 154 × 0.21 = roughly €32
That's a long way from the amounts people imagine. The same unit used in heating mode all winter, however, is an entirely different scale: 6 kWh/day over 150 days, i.e. 900 kWh, about €190. And that's precisely where an air-to-air heat pump becomes attractive, since an electric convector heater would have consumed three to four times more for the same comfort.
| Use case | Typical annual consumption | Annual cost (€0.21/kWh) |
|---|---|---|
| Cooling only, 1 room, average summer | 100 to 200 kWh | €21 to €42 |
| Cooling, 3-room multi-split, heatwave summer | 400 to 700 kWh | €84 to €147 |
| Main heating, two-bedroom flat, air-to-air heat pump | 1,800 to 3,000 kWh | €380 to €630 |
| Supplementary heating, 1 room | 500 to 900 kWh | €105 to €190 |
These ranges line up with the orders of magnitude published by ADEME in its guides on summer comfort and heating, as well as the benchmarks issued by the Observatoire national de la précarité énergétique. They assume a correctly sized and well-maintained unit.
The five factors that really send the bill off course
Once measurement is in place, you can test changes and see their effect in figures. Here, in decreasing order of impact, is what moves the needle most.
The temperature setpoint
By far the number one lever. Every degree the setpoint is lowered in summer increases consumption by roughly 7 %, an order of magnitude consistently cited by ADEME. Going from 26 °C to 22 °C isn't "a bit more": it's close to 30 % extra consumption, often for less comfort (thermal shock on entering the room, overly dry air, waking up at night).
The health recommendation remains a maximum gap of 5 to 7 °C with the outdoor temperature. At 34 °C outside, aiming for 27 °C indoors is both cheaper and healthier.
Untreated solar gain
An unshaded west-facing picture window can inject 400 to 700 W of heat per square metre in the late afternoon. The air conditioning then spends its time removing what the sun keeps adding. Thermal blackout blinds or a reflective film fitted on the outside cut the load dramatically — far more than swapping out the unit.
Clogged filters and heat exchanger
A blocked filter reduces airflow, hence heat exchange, hence efficiency. The unit compensates by running longer. The order of magnitude commonly accepted in the trade: 5 to 15 % excess consumption for a filter neglected across an entire season. Cleaning takes five minutes with lukewarm water, once a month during periods of heavy use. A small air conditioner cleaning kit with a fine brush and disinfectant spray for the heat exchanger usefully rounds out the job, without replacing annual servicing by a professional.
Needless start-stop cycling
A modern inverter air conditioner is designed to modulate continuously, not to switch on and off. Turning the unit off when you leave for work and then blasting it on your return generally costs more than leaving it at a sensible setpoint in eco mode, in a well-insulated home. Here again, measurement settles the debate within a week of testing.
A badly positioned outdoor unit
A unit that draws in its own hot air, boxed into an overly enclosed casing or pressed against a sun-baked wall, sees its condensing pressure climb and its efficiency fall. Manufacturers recommend clearances of at least 20 to 30 cm at the rear and 1 m in front, with no recirculation. A simple shading canopy — never an enclosed cover — can gain several efficiency points.
Tracking your consumption over time
Measuring once is instructive. Measuring continuously is what changes habits for good.
Many air conditioners sold since 2023 include a Wi-Fi module that reports an estimated consumption figure in the manufacturer's app. That data is calculated, not measured: it's useful for trends, less so for absolute values. Cross-check it at least once against a real measurement so you know its bias.
For those who want to go further, a connected electricity consumption monitor installed at the consumer unit lets you visualise each circuit's share in real time. Some models perform appliance recognition and automatically isolate the air conditioning from the rest. It's also an excellent tool for aligning your usage with the new off-peak windows, now partly positioned in the afternoon during summer to absorb solar PV output.
One final habit, often overlooked: also measure the actual temperature in the room, independently of the unit's own sensor. That sensor sits inside the indoor unit, high up, often in a disturbed airflow — it can read 24 °C when it's 27 °C at sofa level. An indoor thermo-hygrometer placed at occupant height, away from the airflow, reconciles the figures and stops you lowering the setpoint unnecessarily. Relative humidity matters just as much as temperature, incidentally: at 45 % humidity, 27 °C is perfectly bearable; at 70 %, the same temperature feels stifling.
What to remember before the next bill
The heart of the matter fits into one sentence: air conditioning isn't expensive for cooling, it's expensive for heating — and that's precisely where it pays off best compared with a convector heater or an oil-fired boiler.
The approach itself fits into four steps:
- set up a measurement (Linky, plug-in meter, modular meter or connected clamp);
- record a representative week of operation;
- convert to euros using your tariff's price per kWh, distinguishing peak and off-peak hours;
- test one change at a time — setpoint, shading, filters — and check the measured effect.
Along the way, this measurement has a value that goes beyond the bill alone: it documents how your installation behaves. Consumption climbing 20 % under identical conditions from one year to the next is a drift signal — low refrigerant charge, fouled heat exchanger, tired compressor — well before the breakdown occurs. No warning light will tell you; the meter will.
Key takeaway: measure before replacing the unit. A €3,500 replacement to gain one SEER point is rarely worthwhile when a €200 external blind and two degrees on the setpoint do better.
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