We all take electricity for granted nowadays, and in the UK we’re lucky to have a reliable and mostly uninterrupted service. But that reliability can be a double-edged sword, because when the power does go down, most of us are quite unprepared for it.
Every year, millions of us face power cuts, which can last anything from seconds to weeks, depending on the severity and the cause. According to Sunsave (which is, admittedly, a solar panel installer!), each home can expect 0.4 outages a year, or four every ten years. Whether you think that’s a lot or not many really comes down to your own expectations, and perhaps how vital it is that you have an uninterrupted supply of electricity.
Power outages certainly feel like they are becoming more frequent, and climate change, which is changing the patterns of wind and storms in the UK, is thought to be behind it. Every winter, heavy storms bring down power lines and leave thousands of households without power in this country. And to be fair, the power companies work incredibly hard, often in the eye of the storm, to restore them.
Of course, it’s not always due to the weather. Roadworks occasionally damage a power line, and there are sometimes technical failures and substation fires, like the one that closed down Heathrow Airport in March 2025. There are also planned outages, where power is cut off due to essential maintenance – but at least you’ll get prior warning of these.
On the home front, power outages can be inconvenient or dangerous, depending on the duration, the season, and what you use the power for. One thing that often goes forgotten when power outages are being discussed is our speciality – boilers.
Boilers have two main issues where power cuts are concerned: shutting down unexpectedly, and failing to restart once the power is restored. In this article, we’ll look at both issues and how to deal with them.
Why boilers cut out during a power cut
A boiler needs three ingredients to keep working – gas, water and electricity. The gas boils the water, and although the water that heats your radiators is a closed loop, fresh water needs to come into be heated up for the tap (in a combi boiler) or the cylinder (in a system or heat-only setup).
So what about the electricity? Boilers rely on power completely to operate. There are the functional parts, like pumps, fans and ignition systems, without which the boiler simply won’t work. Then there are things like thermostats, control panels, electronic control systems, gauges, switches, valves and safety trips, which all need electricity to keep you in control and safe.
So as soon as your boiler loses power, it will stop pretty much in the state it was in at that moment. If you’re running hot water through a combi boiler, it will probably just start running cold. Radiators will cool down, and no hot water will flow into your cylinder – and you can forget about your immersion heater kicking in!
Generally speaking, you won’t need to do anything specific to your boiler in the event of a power cut. Without electricity, it simply won’t operate, so you shouldn’t be wasting gas or causing a build-up – it’ll just be off. However, if you want to turn off the gas, you won’t harm the system. You might want to turn off the boiler at its switch, which could prevent damage if there’s a power surge when the electricity switches back on, but again, it’s unlikely that this will happen.
Why boilers don’t restart after power cuts
After the power is restored, your boiler will probably restart itself as normal, and you’re good to go. However, there’s a chance it will remain switched off. This is usually because some safety feature has been activated to prevent a build-up of pressure or temperature in the boiler. Sometimes the electronic control system will reset itself and will await a manual input to get going again. There are also timers to consider – they are often not saved, and need constant power. If they lose power, they’ll go back to factory settings. In older boilers, it’s possible that there could also be issues with the pilot light.
Initial safety checks
If the power goes out, as long as you have a relatively modern boiler, it is overwhelmingly likely that you’ll be completely safe. They are designed to be safe in exactly these circumstances, so apart from the inconvenience and cold, you shouldn’t worry too much about safety. To all intents and purposes, it should be more or less like switching the boiler off, minus the timers and control panels.
Still, it’s worth keeping an eye on everything, and being especially vigilant about gas. If you smell gas, call a Gas Safe engineer immediately, open windows and get out of the house. If you know where the main gas valve is, turn it off (it’s normally next to your meter).
What to do next
If your boiler doesn’t simply switch itself back on when the power re-starts, run through this checklist:
- Check the boiler display for error codes
- Make sure there’s power (if the display is on, power is on)
- Reset the boiler (check your boiler’s manual for instructions)
- Check and adjust the thermostat
- Reprogram the timer
- Check boiler pressure gauge if it’s low, fill it with the filling loop
- Bleed radiators to remove airlocks
- Check for frozen pipes (if it’s winter)
If all these steps fail to get the boiler working, it’s possible that the power cut has damaged something, perhaps the main circuit board, or blown a fuse. That’s when it’s time to call a professional plumber.
If you’re in the Milton Keynes area, Able Plumbing Solutions are always on call, and we’ll come and have a look at your boiler as soon as we can. We know most boilers inside out, and could have you up and running in no time.