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7 common heating mistakes wasting your money – and how to avoid them
With over a decade of experience at Which?, Tom covers everything from tech advice to money-saving tips, and highlights the best deals during major sales events.
With temperatures dropping and households switching their heating back on, keeping your home warm can take up a significant chunk of your energy bills. Gas and electricity prices are very high this year, which means even small mistakes can end up costing you more than you realise.
For example, you might be tempted to crank up the thermostat to warm your home faster, or rely on an electric heater that's expensive to run. Heating unused rooms or blocking radiators with furniture can also push costs up.
Below, we’ve rounded up some common heating mistakes that could be costing you money, plus simple, practical ways to avoid them and keep your home warm for less.
1. Turning the thermostat up too high
At a glance: Turning the thermostat up won’t heat your home faster. It simply means your heating will stay on for longer to reach the higher temperature.
For most central heating systems, turning your thermostat higher won't heat your home any faster. It sets the temperature you want to reach, rather than making your heating work more quickly.
If you set the temperature to 25°C instead of 20°C, for example, your radiators don't get hotter. Instead, your heating system will keep running for longer until the higher temperature is reached, potentially wasting energy and pushing up your bills.
According to the Energy Saving Trust, turning your thermostat down by just one degree, from 22°C to 21°C, could save you around £120 a year on your energy bills in Great Britain.
To keep costs down, aim for the lowest temperature you feel comfortable with. Using a timer, either built into your heating controls or through a smart thermostat, can also help ensure your heating is only on when you need it (See also: Best smart thermostats).
While lowering your thermostat can help cut costs, it’s important not to let your home get too cold. The NHS recommends heating rooms you regularly use, such as your living room and bedroom, to at least 18°C if possible. This is particularly important if you have a health condition.
If you want to make sure your thermostat and radiator valves are working together efficiently, read our guide to avoiding a common radiator mistake.
2. Having your boiler flow temperature set too high
At a glance: Lowering your combi boiler's flow temperature from 75-80°C to 60°C or below can save the typical household £57 a year, without affecting your home's comfort level.
The heating flow temperature of your boiler is the temperature at which water leaves your boiler on its journey to your radiators.
It's different to the setting on your thermostat. For example, if you set your thermostat to 19°C, your boiler then heats water much hotter than that and sends it to your radiators to warm your home until the air around the thermostat reaches 19°C.
By default, many boilers are set to heat this water to 75-80°C. But many homes with condensing combi boilers can be suitably warmed with heating flow temperatures of 60-65°C or lower. Lowering that temperature means your boiler uses less gas and operates more efficiently.
Research foundation Nesta has estimated that in winter 2026, the average home could save around £57 a year by making the switch. Your home won't be colder, as your thermostat will still be set at the same temperature, but it may take a little longer to warm up.
You can adjust your flow temperature yourself, and tweak it if you feel it's not right for your home. Follow the steps in Nesta's Money Saving Boiler Challenge to do it yourself.
Get more details in our guide to your boiler's flow temperature. Note that this only applies to combi boilers. If you have a water tank you shouldn't adjust the temperature without consulting an engineer.
3. Heating all rooms to the same temperature
At a glance: Heating rooms you aren't using during the day to the same temperature as your main living spaces can waste energy and push up your bills.
If you have a spare bedroom or another room that rarely gets used, you might be wasting money by heating it to the same temperature as the rest of your home. This is particularly true in homes with poor insulation (See also: How to insulate your home).
Radiators in unused rooms still draw heat from your central heating system, so consider installing thermostatic radiator valves (TRVs) so that you can reduce their temperature while the rest of your home is heating up. Avoid switching them off completely during cold weather, which increases the risk of condensation and damp, but a TRV setting of 3 can keep the chill away without using as much energy.
TRVs can also be usful in bedroooms, as you can keep the temperatures lower than in your daytime living spaces.
Smart radiator valves go one step further. These give you room-by-room control via an app on your smartphone, allowing you to adjust temperatures in individual rooms without having to manually change each radiator valve. So you could keep your bedroom cooler during the day, for example, and set its radiator to turn on for an hour or two before you go to bed.
The research foundation Nesta estimates that by making a 1.5°C change in rooms outside the living room, by changing radiator settings from 5 to 3, individual gas households can save £41 a year.
We've tested a selection of smart radiator valves and ranked them on ease of use and features. See our guide to the best smart radiator valves.
4. Placing furniture in front of radiators
At a glance: Blocking radiators restricts the flow of warm air around your room, which can make your heating run for longer and cost more.
You might be tempted to hide an unsightly radiator behind furniture to save space or make your room look neater, but it’s generally not a good idea.
Despite the name, radiators warm rooms partly through convection, where cold air around the radiator is warmed up, rises and spreads around the room, while cooler air moves in to take its place. If a radiator is blocked by furniture, curtains or a cabinet, that warm air can't circulate properly.
When heat is trapped behind sofas, beds or cabinets instead of reaching the room, your home can feel colder even with the heating on. Depending on where your thermostat is positioned, this could mean your heating stays on for longer to reach the desired temperature, wasting energy and pushing up your bills.
To help your radiators work efficiently, keep the space around them as clear as possible. Even moving furniture a short distance away can help heat circulate more freely around the room.
You could also consider fitting radiator reflector panels, which sit behind the radiator and help reduce heat loss through the wall. These are generally most useful for radiators on external walls, particularly where insulation is poor.
5. Using a poor electric heater
At a glance: Which? testing reveals big differences in how quickly electric heaters warm a room, how easy they are to use and how much they cost to run.
Not all electric heaters are equal, so it pays to check our reviews before buying. While some are cheap to buy initially, a heater that struggles to warm your room or uses a lot of electricity could leave you with higher bills than expected.
We've tested electric heaters from big-name brands including DeLonghi, Dyson, Dimplex and Pro Breeze. For each one, we've assessed the running costs, heating performance and ease of use.
One of our top-scoring electric heaters warms a room quickly and evenly, costing around 49p an hour to run. Meanwhile, a lower-scoring model heats up quickly but struggles to distribute warmth evenly, despite costing around 66p an hour to run.
If you're only using one room, an electric heater can sometimes be a cheaper option than heating your entire home. However, while they're useful for a quick burst of warmth, running one for long periods can become expensive. Central heating is generally better suited to maintaining a comfortable temperature throughout your home.
To keep costs down, use your heater's thermostat and timer, if it has them, to avoid heating a room unnecessarily. A lower power setting can also reduce electricity consumption, although it may take longer to warm the room. Remember that actual running costs will depend on your electricity tariff, the heater's power setting and how often its thermostat switches it off.
See our guide to the best electric heaters to discover which models impressed our experts.
6. Not checking your boiler pressure
At a glance: Low boiler pressure can stop your heating from working properly, leaving radiators cold or causing your boiler to shut down.
On many modern boilers with sealed heating systems, you can check the pressure using a gauge on the front of the unit or a digital display. When the system is cold, the recommended pressure is often around 1.0 to 1.5 bar, though you should always check your manufacturer’s instructions.
If the pressure drops below the recommended level, your boiler might need repressurising. Some systems allow you to do this yourself using the filling loop, but you should follow the manufacturer's instructions carefully. If you're unsure, contact your boiler manufacturer or a qualified heating engineer.
If the pressure drops again soon after being topped up, it could indicate a leak somewhere in the system. In this case, you should contact a qualified heating engineer, such as one vetted by Which? Trusted Traders, to investigate and fix the problem.
An annual boiler service can help keep your boiler running safely and reliably, while identifying potential problems before they become more serious.
Boilers involve gas, hot water and electrical components, so certain repairs should always be left to a qualified professional. If you have a gas boiler, use a Gas Safe registered engineer for:
- Repairs involving the boiler's internal gas components. Don't remove the boiler casing to attempt repairs yourself.
- Work on the gas supply, gas pipework or gas meter.
- Investigating persistent pressure problems, including faults with the boiler's expansion vessel.
If your boiler needs a repair, read our guide on common boiler problems and repair costs to make sure you're not paying over the odds.
7. Ignoring draughts and poor insulation
At a glance: Draughts and poor insulation allow heat to escape from your home, making it harder to stay warm without spending more on heating.
Even if you’ve set up your heating correctly, draughts can make your home feel colder than it should.
Gaps around doors, windows, floors and loft hatches allow warm air to escape and cold air to creep in, forcing your heating to run for longer to maintain a comfortable temperature. Don't forget smaller gaps around letterboxes and keyholes, either. (See also: How to draughtproof your home.)
Poor insulation has a similar effect. If your home lacks adequate loft, wall or floor insulation, it can lose heat quickly, meaning you're paying to replace warmth that's escaping from your home.
The good news is that you don't always need to take on major building work to see an improvement. Simple jobs such as fitting letterbox brushes, sealing gaps around windows and doors, or adding thick curtains and rugs can all help reduce heat loss. You can also use a chimney draught excluder if you have an unused fireplace, but make sure it's suitable and remove it before lighting a fire. Never block ventilation that's needed for a gas appliance.
If you want to go a step further, topping up loft insulation is one of the most effective ways to reduce heat loss, particularly in older homes where existing insulation may be thin or missing.
One thing to do this weekend to boost your insulation – find out how to improve your insulation and cut your energy costs no matter what your enthusiasm level is.
