As summer is in full swing across the UK, most people aren’t giving a second thought to their boiler.
However, a heating expert has warned that neglecting your boiler during the warmer months could silently increase energy bills for homeowners and lead to expensive issues when winter comes around.
Stephen Day, a Heating Engineer at iHeat, suggests that common practices such as unnecessarily leaving your boiler on, using inefficient hot water settings, or skipping seasonal maintenance could be wasting more energy than you realise. “People often assume their boiler isn’t using much energy in the summer, but that’s not always true,” Day clarifies.
“Far too often, households are unknowingly paying for hot water they’re not using efficiently, or running outdated systems that quietly waste gas even when radiators are off.”
Considering the pressure on household budgets and the July 2025 energy price cap setting gas at 6.33p per kWh and electricity at 25.73p per kWh, even minor inefficiencies can result in surprisingly high bills over time.
With many of us unwittingly wasting energy through our boilers during the warmer months, Day reveals the main ways this could be happening and what you can do to prevent it:.
Keeping the boiler on when it’s not needed
A lot of UK households habitually keep their boilers running, even when they’re not actively using heating or hot water.
“Some boilers remain on standby and constantly monitor for demand, using energy even when nothing’s being used,” says Day. “Others keep heating water to high temperatures around the clock, resulting in gas consumption you’re still footing the bill for, even in July.”
To minimise waste, it’s worth checking if your boiler has a summer mode or eco setting. If you have a hot water tank, consider lowering the thermostat to around 55°C, which is plenty warm enough for household use, but not unnecessarily high.
Inefficient water heating setting
“Many homeowners leave their boilers on ‘winter mode’ all year,” says Day. “That means they’re heating water to higher-than-needed temperatures or circulating heat through systems that aren’t being used.”
If your water feels scalding or you’re only using hot water a couple of times per day, it’s time to reassess. According to Day, switching to timed hot water schedules or reducing your target temperature can help cut wasted energy.
“One simple way to do this is by using a programmable thermostat or smart controller to schedule hot water only when needed, whether in the morning or evening. It’s an easy change that can reduce your gas usage by several kilowatt hours a day.”
Skipping summer maintenance checks
Just because your boiler isn’t warming your home doesn’t mean it’s not developing problems.
“Summer is the ideal time to check your boiler’s health when it’s not under strain,” Day advises. “Issues like limescale buildup, low pressure, or worn-out parts can all deteriorate without use. Then suddenly, when winter arrives, you’re left with no heating and a hefty repair bill.”
Arranging a summer boiler inspection can help detect problems early, often saving you hundreds on emergency callouts later. Some problems, like sediment in hot water tanks or stuck diverter valves, are common in older systems and can be easily rectified if caught early.
Your boiler might be ‘on’ even when you think it’s off
“One sign your boiler is wasting energy is if it’s firing up randomly, even when you’re not using hot water,” Day cautions. “That could mean it’s maintaining tank temperature unnecessarily or cycling due to faulty sensors.”
So, if you hear your boiler clicking during the day without demand, it’s worth investigating.
Keeping an eye on your energy use will help. If your gas consumption remains high despite not using the heating, your boiler might be the culprit.
In that case, an engineer can assist by adjusting settings or recommending upgrades.
While a few kilowatt-hours here and there might not seem like much, it adds up. For instance, a household with a 30kW boiler that runs inefficiently for just one extra hour a day over three months could waste over 170 kWh of gas, costing over £10 for nothing.
“If you combine that with poor settings and no maintenance, you could easily be wasting £30 or more every summer,” says Day. “That’s money better spent elsewhere.
“As we all look for ways to save, the boiler is a great place to start,” Day concludes. “Just because it’s not heating your home doesn’t mean it’s not costing you. A few simple changes today can mean lower bills tomorrow and a warmer, stress-free winter.”
The advice follows after one individual on Reddit revealed their strategies to slash electricity bills after claiming they previously received astronomical bills during summer.
Their recommendations to reduce your summer electricity costs included conducting an electricity audit, inspecting for air leaks, changing the air filter, monitoring phantom energy and setting your thermostat properly.
