What Temperature Should I Set My Air Conditioning To?

One of the most common questions we hear from homeowners and businesses after having air conditioning installed is: what temperature should I actually set it to? It is a great question, and the answer depends on a few factors including the time of year, the type of room, and whether you are more concerned with comfort or keeping energy bills low.

In this guide, we share the recommended temperature settings for air conditioning in UK homes and offices, explain how to get the most out of your system, and offer some practical tips to help you stay comfortable without running up unnecessary costs.

What Is the Ideal Air Conditioning Temperature in the UK?

For most homes and offices in the UK, the recommended air conditioning temperature during summer is between 21°C and 24°C. This range is widely considered the sweet spot for comfort cool enough to feel the benefit, without being so cold that it becomes uncomfortable or wastes energy.

The Health and Safety Executive (HSE) recommends that workplace temperatures should be at least 16°C in most environments, while the World Health Organisation (WHO) advises keeping indoor temperatures below 24°C during hot weather for general wellbeing. Setting your AC somewhere in the 21-24°C range aligns with both guidance.

Quick answer: For most UK homes and offices, setting your air conditioning to between 21°C and 24°C in summer provides the best balance of comfort and energy efficiency.

Does the Ideal Temperature Vary by Room?

Yes! Different rooms have different needs, and it is worth adjusting your settings accordingly if your system allows it.

Living Rooms and Open Plan Spaces

For living rooms and open plan areas where people are active or moving around, 21-23°C is a comfortable target. These rooms tend to have more heat sources like TVs etc so slightly lower settings can help offset that.

Bedrooms

Sleep quality is heavily affected by room temperature. Research from the Sleep Foundation suggests the ideal sleeping temperature is between 16°C and 18°C. If you have air conditioning in your bedroom, setting it slightly lower than daytime levels around 18-20°C overnight can significantly improve the quality of your sleep during warm summer months.

Home Offices

Studies suggest that productivity peaks when office temperatures are between 21°C and 22°C. Too warm and concentration suffers; too cold and people become uncomfortable and distracted. If you work from home, keeping your space in this range during working hours is a good starting point.

Kitchens

Kitchens generate significant heat from cooking, so a slightly lower target of 19-21°C can help counteract this. Bear in mind that your AC will need to work harder in a kitchen environment.

Loft Conversions and Conservatories

Lofts and conservatories are often the hottest rooms in a property during summer due to less insulation and direct sun exposure. These spaces may need the AC set lower, around 20-22°C to achieve the same level of comfort as the rest of the house.

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What Temperature Should I Set My AC to in an Office or Commercial Building?

In commercial settings, the right temperature depends on the type of business and how many people are in the space. As a general rule:

• Offices: 21-22°C is the most commonly recommended range for desk-based work environments
• Restaurants and cafes: 20-22°C works well for diners, though kitchens will need separate consideration
• Retail shops: 19-21°C is comfortable for customers browsing, especially when footfall is high
• Gyms: 16-19°C is more appropriate where people are exercising and generating significant body heat
• Server rooms: typically require a much lower and tightly controlled range of 18-27°C as specified by equipment manufacturers

The HSE recommends that employers maintain a reasonable temperature in the workplace. In practice, this means ensuring staff are neither too hot nor too cold to work comfortably and safely.

How Does Air Conditioning Temperature Affect Energy Bills?

Every degree you lower your thermostat increases energy consumption. As a rough guide, reducing your target temperature by just 1°C can increase your energy use by around 8-10%. This means that if you set your AC to 18°C on a hot day rather than 22°C, your system is working harder.

The Energy Saving Trust advises setting your thermostat to the highest temperature at which you feel comfortable, rather than the lowest you can tolerate. For most people in the UK, that is around 21-23°C in summer.

Tips to Keep Costs Down

• Set the temperature no lower than 21°C during the day unless there is a specific reason to go cooler
• Use a timer or schedule so the AC only runs when the room is occupied
• Keep windows and doors closed when the AC is running to prevent cool air escaping
• Use ceiling fans alongside your AC they help circulate cool air and allow you to set a slightly higher temperature without losing comfort
• Close blinds or curtains on south-facing windows during the hottest part of the day to reduce solar heat gain
• Have your system serviced regularly a well maintained AC runs more efficiently and costs less to operate

Most modern air conditioning systems particularly inverter-driven units are highly energy efficient when used correctly. Setting a sensible target temperature and allowing the system to maintain it steadily is far more efficient than frequently switching it on and off.

What About Using Air Conditioning for Heating in Winter?

Most modern air conditioning systems installed in UK homes are reverse cycle systems, meaning they can provide both cooling in summer and heating in winter. When using your AC for heating, the recommended target temperature is between 19°C and 21°C broadly the same as a central heating system.

Using your AC to heat your home is often significantly more energy efficient than electric heaters, and can even be cheaper to run than a gas boiler in milder weather. If you would like to know more about how your system performs in heating mode, our service and maintenance team can advise you during a routine visit.

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Why Is My Air Conditioning Not Reaching the Temperature I Have Set?

If your system is struggling to reach or maintain your chosen temperature, there are a few possible causes:

• The air filter is dirty and restricting airflow. Clean it every four to six weeks during regular use
• The unit is undersized for the room; a system that is too small will struggle to cool a large space
• Doors and windows are open, allowing warm air in
• The system needs a service; reduced efficiency over time is common without regular maintenance
• Refrigerant levels are low; this requires an F-Gas certified engineer to diagnose and resolve

If your AC is running but the temperature in the room is not dropping to the level you have set, it is worth contacting a qualified engineer. Our service and repair team can carry out a full diagnostic check and get your system performing properly again. For urgent issues, we also offer an emergency callout service across Essex, Hertfordshire, London and surrounding areas.

Conclusion

For most UK homes and offices, setting your air conditioning to between 21°C and 24°C in summer provides the best balance of comfort and energy efficiency. Bedroom temperatures can be set slightly lower at night to improve sleep, while commercial spaces may need adjustment based on occupancy and activity levels.

Avoid the temptation to set the temperature as low as possible as it makes your system work harder, costs more, and rarely feels more comfortable. A consistent, sensible setting with a well-maintained system will always deliver better results.

With over 16 years of experience installing and maintaining air conditioning systems across Essex, Hertfordshire, London and Cambridgeshire, the Evergreen team is here to help. Whether you need a new installation, a service or just some friendly advice, get in touch with us today.

For more information about our air conditioning services, visit our FAQ page here!