How much does an air conditioner consume? Complete guide to saving money

Discover how to optimise the use of your air conditioner, read consumption in your bill and choose the most efficient technology for your home.

The air conditioner is an essential ally for home comfort, but how much does it really affect energy expenditure? Knowing the consumption of your system is not just a technical detail: it is practical information that allows you to avoid waste and keep your bill under control.

In this guide, we explore everything you need to know: from the kWh consumed every hour to tips for heating and cooling your home intelligently.

How much does an air conditioner consume in one hour?

The hourly consumption of an air conditioner mainly depends on its thermal output, expressed in BTU/h (British Thermal Unit) or kW, and on its seasonal energy efficiency (SEER), the index that measures how much electrical energy the appliance absorbs for each kWh of cooling produced. The higher the SEER, the less energy the device consumes.

The reference formula is simple: absorbed power (kW el.) = thermal output (kW) / SEER. This methodology is defined by EU Delegated Regulation no. 626/2011 and is the basis of the mandatory ENEA energy label for air conditioners. But it is not just a matter of size: the energy class and inverter technology can make a very significant difference.

Average consumption table (Class A++, typical SEER 6.5–7.0)

Power (BTU)	Thermal output (kW)	Hourly consumption (kWh)	Seasonal consumption* (kWh/year)
7.000 BTU	~2,1 kW	0,30–0,32 kWh	105–112 kWh
9.000 BTU	~2,6 kW	0,37–0,40 kW	130–140 kWh
12.000 BTU	~3,5 kW	0,50–0,54 kW	175–189 kWh
18.000 BTU	~5,3 kW	0,76–0,82 kW	265–286 kWh
24.000 BTU	~7,0 kW	1,00–1,08 kW	350–376 kWh

_{* Seasonal consumption calculated on 350 annual operating hours in cooling mode, the ENEA/EU energy label standard. Absorbed power is calculated as: thermal output (kW) / SEER. Values may vary depending on the model, climate zone and usage habits. Sources: EU Delegated Regulation 626/2011; ENEA – efficienzaenergetica.enea.it; EPREL Register – eprel.ec.europa.eu.}

A 9,000 BTU class A++ model with inverter absorbs an average of 0.37–0.40 electrical kW per hour, with an estimated seasonal consumption of around 130–140 kWh over 350 hours. The same appliance in class C (SEER ~2.8) would absorb around 0.93 kW/h: a difference of 55–60%, equal to tens of euros in the bill each season.

The factors that influence actual consumption

The figure in the table is a starting point, but the actual consumption in your home can vary significantly based on several elements.

Models in class A++ or above guarantee significantly higher efficiency. To guide you on the energy label, also keep an eye on the SEER (seasonal cooling efficiency) and SCOP (seasonal heating efficiency) values: the higher they are, the less energy the appliance consumes for the same performance.

Unlike on/off models, the inverter continuously adjusts power, avoiding repeated restarts and saving up to 30% energy.

Each degree of difference compared to the outside temperature increases consumption. Setting 26°C in summer instead of 20°C can reduce consumption by 15–20%. The WHO recommends not exceeding a 7–8°C difference between indoors and outdoors.

A poorly insulated room, with windows exposed to the sun or poorly insulated walls, forces the air conditioner to work harder and longer to maintain the set temperature.

Dirty filters reduce airflow and system efficiency, with a measurable negative impact on consumption. Cleaning them every 2–4 weeks during use is a simple and practical good habit.

Installed in a shaded and well-ventilated area, the outdoor unit works in optimal conditions, reducing the compressor’s effort and consumption.

The most recent models use R32 gas, with a lower global warming potential (GWP) than traditional refrigerants. A choice that reduces environmental impact without compromising performance.

How to calculate the cost of the air conditioner in your bill

Estimating how much it costs to use the air conditioner over a season is simpler than it seems. The basic formula is:

Cost = Absorbed power (kW) × Hours of use × Price per kWh

Practical example: a 9,000 BTU A++ inverter air conditioner, with an average absorbed power of around 0.39 kW, used 6 hours a day for 90 days (a typical summer season), with an energy cost of €0.30/kWh (including system charges, excise duties and 10% VAT, source ARERA 2024–2025):

0.39 kW × 6 h × 90 days × €0.30 = ~€63 per season

With a class C model (SEER ~2.8, without inverter), the same nominal power absorbs ~0.93 kW/h, bringing the seasonal cost to around €150. A difference of around €90 per season, every year.

Fixed or portable air conditioner: consumption comparison

A portable air conditioner is often considered an economical alternative, but from a consumption point of view, the situation is more complex.

Single-hose portable air conditioners are generally less efficient: they release into the environment part of the heat they should expel, forcing the compressor to work harder. The result is generally significantly higher consumption than fixed split units with the same BTU.

Dual-hose air conditioners are more efficient than single-hose portable units, but still remain below the performance of a fixed split system with inverter technology.

For those who use the air conditioner regularly, the fixed air conditioner is almost always the most cost-effective choice in the medium to long term.

How much does the air conditioner consume in heating mode?

Modern heat pump air conditioners are not only used to cool in summer: by reversing the thermal cycle, they heat the home in winter with higher efficiency than traditional electric resistance systems.

An inverter air conditioner with heat pump can provide up to 3–4 kW of thermal energy for every kW of electrical energy consumed (COP of 3–4). In practice, the same appliance that absorbs 1,000 W can generate up to 3,000–4,000 W of heat, making it three times more efficient than a traditional electric radiator.

In heating mode, a 9,000 BTU model consumes an average of 0.85 kWh, while a 12,000 BTU model consumes around 1.1 kWh. Latest-generation inverter models maintain good performance even at very low outdoor temperatures (down to -15°C/-25°C in advanced models), although optimal performance is expressed in intermediate seasons and temperate climates. In contexts with particularly harsh winters, it is advisable to check the specifications of the chosen model or combine it with a backup heating system.

Air conditioner incentives: what the regulations provide for

Those who purchase a new air conditioner can access tax benefits that reduce the cost of the investment. Here are the main options available.

50% tax deduction: the 2025 Budget Law provides for the possibility of deducting 50% of the expense over 10 years in the tax return (Form 730). Payment by dedicated bank transfer is mandatory.

Conto Termico: it incentivises the replacement of air conditioning systems with heat pumps. The value of the contribution can reach up to 65% of the expense, depending on the performance of the new system and the climate zone. The incentive can be transferred to the installer as an immediate discount on the price.

Please note: the Conto Termico applies only to systems with a heat pump function (heating and cooling), not to air conditioners with cooling mode only.

How to reduce air conditioner consumption: 5 practical tips

Choosing an efficient model is the first step, but usage habits make just as much difference. Here are five practical measures.

Each degree lower increases consumption by around 7–10%. A value between 24 and 26°C guarantees comfort without waste.

Scheduling it to turn on 30 minutes before returning home and avoiding leaving it on at night (if the outside temperature allows it) significantly reduces consumption.

Reducing heat gains from outside means less work for the air conditioner.

Every 2–4 weeks during the season. It is a simple operation that keeps efficiency at its maximum.

In very humid environments, reducing humidity makes heat feel less oppressive, allowing you to set a higher temperature without losing comfort.

The right choice to consume less

Understanding how much an air conditioner consumes is the starting point for making more informed choices: from the right size for each environment to the energy class, from inverter technology to daily usage habits. Each element contributes to determining how much you will find in your bill at the end of the season.

If you are considering purchasing or replacing your system, Enel offers a range of low-consumption air conditioners designed to heat in winter and cool in summer while reducing consumption all year round.