A heating expert has warned that making a few simple mistakes during the warmer months could silently drive up your energy bills and set you up for costly problems when winter returns
With summer at its peak across Britain, the last thing on most people’s minds is their boiler. However, a heating expert cautions that neglecting your boiler during the warmer months could quietly inflate your energy bills and leave you facing expensive issues when winter arrives.
Stephen Day, Heating Engineer at iHeat, reveals that typical behaviours, such as leaving your boiler running unnecessarily, utilising inefficient hot water configurations, or avoiding seasonal servicing, might be squandering 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 explains. “Far too often, households are unknowingly paying for hot water they’re not using efficiently, or running outdated systems that quietly waste gas even when radiators are off.”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 finances and the July 2025 energy price cap setting gas at 6.33p per kWh and electricity at 25.73p per kWh, even small inefficiencies can result in surprisingly steep bills over time.
With many of us inadvertently squandering energy through our boilers during the milder months, Day reveals the primary ways this might be occurring and what you can do to prevent it:.
Keeping the boiler operational when it’s not required
Numerous British households maintain their boilers running through routine, even when they’re not actively utilising heating or hot water. “Some boilers remain on standby and continuously monitor for demand, using energy even when nothing’s being used,” explains Day.
“Others persistently heat water to high temperatures, leading to gas consumption you’re still paying for, even in July.”
To minimise waste, it’s worth investigating whether your boiler has a summer mode or eco setting. If you possess a hot water tank, consider adjusting the thermostat to approximately 55°C, which is sufficiently warm for domestic use, without being excessively high.
Inefficient water heating setting
“Many homeowners keep their boilers on ‘winter mode’ throughout the year,” Day points out. “This means they’re heating water to higher-than-necessary temperatures or circulating heat through systems that aren’t in use.”
If your water feels too hot or you’re only utilising hot water a few times daily, it’s time to re-evaluate. Day suggests that switching to timed hot water schedules or lowering your target temperature can help reduce wasted energy.
“A straightforward way to achieve this is by using a programmable thermostat or smart controller to schedule hot water only when required, be it in the morning or evening. It’s a simple adjustment that can decrease your gas usage by several kilowatt hours a day.”
Not doing summer maintenance checks
Just because your boiler isn’t warming up the house doesn’t imply it’s trouble-free.
“Summer is the best time to check your boiler’s health when it’s not under pressure,” Day suggests. “Things like limescale buildup, low pressure, or worn-out parts can all worsen without use. Then suddenly, when winter hits, you’ve got no heating and a big repair bill.”
Arranging a summer boiler inspection can spot issues early on, potentially saving you a fortune in emergency callouts down the line. Certain problems, such as sediment in hot water tanks or jammed diverter valves, are typical in ageing systems but can be easily remedied if detected promptly.
Your boiler might still be active even when you think it’s switched 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.”
Therefore, if you notice your boiler making noises during the day without any need, it’s time to look into it.
Keeping an eye on your energy consumption is beneficial. If your gas usage stays high even though you’re not heating the home, your boiler could be the culprit.
In this scenario, an engineer can help by tweaking settings or suggesting system upgrades.
Even small amounts of wasted kilowatt-hours can become significant over time. For instance, a household with a 30kW boiler that operates inefficiently for just an extra hour daily across three months could squander upwards of 170 kWh of gas, which equates to shelling out more than £10 for no reason at all.
“If you combine that with poor settings and no maintenance, you could easily be wasting £30 or more every summer,” warns Day. “That’s money better spent elsewhere.”
Day emphasises the importance of boiler efficiency, especially when looking to cut costs. “As we all look for ways to save, the boiler is a great place to start,” he advises.
“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.”
This advice follows a Reddit user’s revelation of their strategies for slashing summer electricity bills after previously receiving exorbitant charges during the warmer months.
Their suggestions for reducing summer electricity expenses include conducting an energy audit, inspecting for air leaks, changing the air filter, monitoring phantom energy, and setting up your thermostat properly.