Keeping Cool in Summer Without a Huge Electricity Bill

Summers are getting hotter in many parts of the world, and with the heat comes a new household expense: cooling. Air conditioners can draw a lot of electricity, and even fans add up when they run for hours every day. Yet much of the work of keeping a home cool can be done for free, by stopping heat getting in and letting it out at the right times. Used thoughtfully alongside those habits, fans and air conditioning can keep a household comfortable without a shocking bill.

This guide explains how homes heat up, how to keep them cooler, and how to run cooling appliances efficiently. During extreme heat, health comes first: follow official heat-health advice in your area, especially for babies, older people and anyone with health conditions.

How homes heat up

Heat enters a home in three main ways:

1. Sunlight through windows, which warms everything it falls on.
2. Warm outdoor air, which leaks in through open windows, doors and gaps.
3. Heat from inside: cooking, appliances, lighting and even people.

Roofs and walls in direct sun also absorb heat during the day and release it into the home later, which is why upstairs rooms and top-floor flats often stay hot into the night. Understanding this helps you decide what to do and when.

Keep the sun out

Blocking sunlight before it enters is one of the most effective cooling measures.

• Close curtains and blinds on sunny windows during the hottest part of the day. Light-coloured or reflective coverings work better than dark ones, which absorb heat.
• External shading is best. Awnings, external shutters, shade sails or even a well-placed parasol stop sunlight before it reaches the glass. Internal blinds help, but some heat still enters.
• Reflective window film on south- and west-facing windows (in the northern hemisphere) reduces heat gain, though it also reduces winter sunlight.
• Plants and climbers shading a wall or window cool a room over time.

Ventilate at the right time

Opening windows is not always the right answer. If the outside air is hotter than the air inside, opening windows lets heat in.

• During the day, when it is hotter outside than inside, keep windows on the sunny side closed and covered.
• In the evening and at night, when the outside air cools, open windows wide to flush out the warm air.
• Create a cross-breeze by opening windows on opposite sides of the home, or on different floors, so cool air flows through. Opening a high window upstairs and a low window downstairs lets warm air rise out and cooler air enter.
• Close windows again in the morning before the outside temperature climbs, trapping the cool night air inside.

Always consider security and safety when leaving windows open, particularly on ground floors and in homes with young children.

Reduce heat from inside

Everyday activities add heat to a home:

• Cook at cooler times of day or use appliances that produce less heat. A microwave, slow cooker, air fryer or outdoor grill adds less heat to the kitchen than an oven running for an hour.
• Run heat-producing appliances at night. Dishwashers, tumble dryers and washing machines add heat and humidity; running them in the cooler evening, ideally with windows open, keeps daytime temperatures lower.
• Switch off unused electronics. Computers, games consoles and televisions give off heat, even in standby.
• Use LED lighting, which produces far less heat than incandescent and halogen bulbs.
• Air-dry laundry outside rather than in a tumble dryer, where possible.

Getting the most from fans

Fans do not lower the temperature of a room; they cool people by moving air across the skin, which helps sweat evaporate. This has two consequences:

• A fan in an empty room achieves nothing. Switch it off when you leave.
• Fans use relatively little electricity compared with air conditioning, so they are a cost-effective first choice.

Ways to get more cooling from a fan:

• Position it to create a breeze across where you sit or sleep.
• Use it to pull cool air in at night by placing it in a window, facing inward when the outside air is cooler, or facing outward on the opposite side to push warm air out.
• Ceiling fans should rotate in the direction that pushes air downward in summer; many have a switch to reverse the direction.
• A bowl of ice or a frozen bottle in front of a fan gives a short burst of cooler air, though the effect is modest.

Using air conditioning efficiently

If you have air conditioning, how you use it determines the bill.

• Set a moderate temperature. Each degree lower increases energy use. Many energy agencies suggest setting cooling to the highest temperature that is still comfortable — often somewhere around the mid-twenties Celsius — and using fans alongside it to feel cooler.
• Cool only the rooms you use. Close doors to unused rooms. Portable or single-room units are most efficient when cooling one room.
• Keep doors and windows closed while the air conditioning runs.
• Use timers and eco modes so units do not run all day in an empty home. Starting the unit a little before you return is usually cheaper than cooling an extremely hot room from scratch at full power.
• Clean or replace filters regularly. Clogged filters reduce efficiency.
• Keep outdoor units clear of leaves, debris and obstructions, and shade them if possible, without blocking airflow.
• Use dehumidify ("dry") mode on humid days; removing moisture can make a room feel more comfortable at a higher temperature.

If you are choosing a new unit, energy efficiency ratings make a large difference to running costs over its lifetime. A correctly sized unit is also important: one that is too small runs constantly; one that is too large cycles on and off inefficiently.

Cooling bedrooms for better sleep

Hot nights disrupt sleep. To keep bedrooms cooler:

• Keep bedroom curtains closed during the day.
• Open windows in the evening once the outside air is cooler.
• Use light cotton or linen bedding, and swap a heavy duvet for a thin sheet.
• Try a fan near the bed, pointed so it moves air across you.
• Cool yourself before bed with a lukewarm shower.
• Keep a glass of water by the bed.
• Sleep downstairs if upstairs rooms are much hotter.

Staying cool without cooling the house

Cooling the person is often cheaper than cooling the room:

• Drink water regularly throughout the day.
• Wear loose, light-coloured clothing in natural fabrics.
• Run cold water over your wrists or use a damp cloth on the neck.
• Spend the hottest hours in the coolest room of the home.
• Visit cool public places — libraries, shopping centres, community centres — during extreme heat; some areas open dedicated cooling centres.

Longer-term improvements

Some changes reduce cooling needs for many years:

• Insulation keeps heat out in summer as well as in during winter, especially loft and roof insulation.
• External shading and awnings on sun-facing windows.
• Light-coloured or reflective roofing where appropriate and permitted.
• Trees and planting that shade the home.
• Efficient cooling systems, such as modern heat pumps that can heat in winter and cool in summer.

Check whether local programmes help with the cost of insulation or efficient cooling.

Heat and health

Heatwaves are dangerous, particularly for babies, young children, older adults, people with heart or lung conditions and people who work outdoors. Health agencies advise recognising the signs of heat exhaustion — such as headache, dizziness, nausea, heavy sweating, cramps and extreme thirst — and acting quickly by moving to a cooler place, drinking water and cooling the skin. Heatstroke is a medical emergency. Check on neighbours and relatives who may be vulnerable, and never leave children or pets in parked cars.

Saving money on cooling should never come at the expense of safety. If someone in your home is at risk, prioritise keeping them cool.

Working out what cooling costs

It helps to know roughly what your cooling appliances cost to run, so you can choose sensibly between them. Every electrical appliance has a power rating in watts, usually printed on a label or in the manual. To estimate the cost of running it:

1. Divide the wattage by 1,000 to get kilowatts.
2. Multiply by the number of hours it runs.
3. Multiply by the price you pay per kilowatt-hour (kWh) on your electricity bill.

For example, a 50-watt fan running for eight hours uses 0.05 × 8 = 0.4 kWh. A portable air conditioner drawing 1,000 watts for the same eight hours uses 8 kWh — twenty times as much. The actual figures depend on the model, its settings and how hard it is working, but the comparison shows why fans should be the first choice whenever they keep people comfortable enough, with air conditioning reserved for the hottest periods or for those who need it most.

Keeping pets and plants comfortable

Pets feel the heat too. Make sure they have shade and plenty of fresh water, walk dogs early in the morning or late in the evening when pavements are cooler, and never leave animals in parked cars. Houseplants near sunny windows may need moving back from the glass and watering more often; grouped together, they also add a little humidity and a sense of coolness to a room.

A summer routine

1. Close curtains and blinds on sunny windows before the sun reaches them.
2. Keep windows closed during the hottest hours if it is hotter outside.
3. Open windows wide in the evening and overnight to flush out heat.
4. Cook and run appliances at cooler times of day.
5. Use fans where people are, and switch them off in empty rooms.
6. If you use air conditioning, set a moderate temperature and cool only occupied rooms.
7. Clean filters and keep outdoor units clear.
8. Keep bedrooms dark during the day and well ventilated at night.

The bottom line

The cheapest cooling is the heat you never let in. Shade windows, ventilate at night, reduce heat from cooking and appliances, and rely on fans before air conditioning. When you do use air conditioning, choose a moderate setting, cool only the rooms you use and keep the system well maintained. These habits keep your home comfortable through the hottest weeks while keeping your electricity bill under control.