Here's why you need an annual boiler service and what to ask your engineer
We've had our first taste of winter this week, with snow in some parts of the UK. If you've not yet had your boiler serviced, now could be a good time to book one in.
Leaving it until the depths of December means you're more at risk of an emergency breakdown leaving you freezing or without hot water right when you most need it.
Good heating engineers' diaries tend to fill up over winter as people start to think about their heating again and emergencies arise.
It's really worth getting your boiler serviced while it's still working, rather than waiting for a potential breakdown that could leave you waiting in the cold.
Here are our top tips when it comes to boiler servicing.
Do I really need to service my boiler every year?
Getting an annual boiler check means your engineer will be able to detect any problems with your boiler before it escalates into a costly repair or replacement. It's also essential for your gas safety at home. And, a well-maintained boiler will operate more efficiently, helping to reduce the amount you pay for energy each month.
If you haven't had your boiler serviced in more than a year, you should contact a boiler engineer and arrange a service. Even if your boiler seems to be working fine on the face of it, it's a great way to make sure your heating is as efficient (read: cheap to run) as possible going into winter.
Plus, it'll flag any faults early, which means cheaper and less urgent repairs. The last thing you want is for your boiler to break down in the depths of winter, just when you need it most and when engineers are likely to be at their busiest.
If your boiler is still within its warranty period, check the terms. Not keeping up with annual servicing can invalidate any warranty you may have on your boiler.
To get the best out of your boiler service, you need to make sure you're hiring the right person for the job, and that you're asking the right questions on the day.
Here are our top boiler servicing tips:
1. Choose a reputable, Gas Safe-registered boiler engineer
The law states that anyone working on a gas boiler must be on the Gas Safe Register. That's for both your safety and theirs.
You can check your engineer's credentials against the online register, call 0800 408 5500 or ask them to show you their Gas Safe Register ID card.
All the heating engineers we list through Which? Trusted Traders are Gas Safe Registered, and go through a rigorous vetting process to ensure we're happy to endorse them.
You can use the search tool below to find your nearest Which? recommended boiler engineer:
2. Find out how much your boiler service will cost
A boiler service will cost you around £80 on average, though some can be up to £120 depending on where you are. If an engineer is quoting a lot more than you expect, you should query why it is, or gather several different quotes before deciding.
The initial price doesn't include any follow-up work that your boiler might need. You'll need to pay for any repairs your engineer needs to make. Common faults, for example, might be that the hot water pump or ignition requires repair, which would cost approximately £280 and £135 respectively.
If your boiler is in good condition, you shouldn't expect there to necessarily be a fault each time but, much like having your car MOT-ed, it's worth going into the appointment knowing that something might crop up that would increase the price.
Paying for boiler cover tends to be more expensive than paying as you go. Find out why, and see our tips if you do decide to buy it, in our guide to boiler cover.
3. Ask what's included in your boiler service
Your Gas Safe-registered engineer will follow a specific checklist when carrying out your boiler service, but it's worth discussing with them what they will be doing and why for your own understanding.
They should verify that all controls are working as they should, test whether the system has the correct degree of pressure, examine the boiler for any indications of corrosion, clean any dirty components and, crucially, confirm that there are no other safety concerns, including gas or carbon monoxide leaks.
If you have a gas boiler then you should also own a carbon monoxide detector. But past Which? research has found that a concerning number of the CO detectors sold online don't work as they should.
Check our carbon monoxide alarm reviews to make sure you buy one that will detect a deadly leak.
4. Ask your engineer to improve your boiler's efficiency
Even if the engineer finds your boiler is in perfect working condition, you should seize the opportunity to get help optimising it for maximum energy efficiency. This will lower your carbon emissions and make your heating cheaper to run over winter.
Ask your engineer about:
- Removing soot from your boiler – soot can build up in your boiler tubes, making your boiler work with a lower heat transfer rate meaning it needs more fuel
- Decreasing the stack temperature – lowering how much operating pressure your boiler has when unused at night or on less cold days
- Using an economiser – this works by using the wasted hot flue gas to heat water that will feed into the boiler, helping to reduce fuel use and preventing the negative impact of your boiler being fed with cold water
- Using a Variable Frequency Drive to reduce your running costs – this allows your system to control its airflow with a fan, resulting in electricity savings
- Setting the right flow temperature for you - more on this below.
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5. Find out how to change your boiler settings yourself to save money and energy
You'd be forgiven for leaving your boiler sitting in a cupboard from one year to the next without having a look at its controls.
But if energy efficiency is on your mind, it's important to understand what you can do to adjust your boiler settings yourself, so ask your engineer about this.
One thing you can do, for example, is adjust your boiler flow temperature. It's easy to do yourself, but your heating engineer will be able to show you how and explain when to make changes.
Your boiler flow temperature regulates the temperature of water your system sends around your home to warm your radiators.
If your home has a condensing combi boiler, you can probably heat your system with a flow temperature of 60-65ºC. A lower flow temperature will use less gas, reducing your energy bill. The temperature should be as low as it can be while still heating your radiators enough to achieve the air temperature set by your thermostat - which of course will trigger your heating to switch off.
The idea is to warm your home with as little energy as possible, not to have your home be cold. So if you find the air temperature is staying low when the heat is on, you'll need to bump the flow temperature back up a little.
There's no one right flow temperature - a variety of factors will determine what works for you, such as your insulation, your radiator size and design, and your desired air temperature.
Your engineer should expect you to care about energy and running costs in the current climate, but they won't necessarily set your boiler up for maximum efficiency unless you explain that this is what you're after. So it's worth emphasising this to them and asking what adjustments you can make yourself over the winter.
Find out more about lowering your boiler's flow temperature to save money.
Do bear in mind that this is only true of combi boilers. Heat-only or system boilers which store hot water in a tank or cylinder need to be hot to reduce the risk of Legionella bacteria propagating and causing Legionnaire's disease. But your engineer may well be able to suggest other ways to improve your running costs - so ask them for their advice.
We surveyed more than 10,000 homeowners to find out about their experiences of getting a boiler service. For a complete rundown of everything you need to think about to keep your boiler working as it should, read our guide to getting the best boiler service.
