Work out what your heating really costs, what a new boiler would save you, what it costs to cook a meal, and where the rest of your bills go. Everything runs in your browser — nothing is sent anywhere.
Heating is usually more than half of a household's energy bill. This works out what yours costs, and what you'd get back by replacing an old boiler.
Work out how much heat a room actually needs. Undersize a radiator and the room never warms up; oversize it and you pay for heat you don't use.
A guide, not a design. Radiator makers quote output at a 50°C temperature difference (delta T50); if your system runs cooler — which it should, for a condensing boiler — you need a larger radiator than the headline figure suggests. Worth a conversation before you buy.
What the code on your boiler display actually means, what you can safely check yourself, and when it needs an engineer.
Never remove the boiler casing or touch anything inside it. Only a Gas Safe registered engineer may work on a gas appliance — it is against the law for anyone else, and it is the part that kills people. Everything suggested below is outside the boiler.
If you smell gas: don't touch any switch. Open the windows, turn the gas off at the meter if you can reach it safely, get everyone out, and ring the National Gas Emergency Service on 0800 111 999 from outside.
Something's gone wrong and you're not sure how bad it is. Start here.
The same applies if a carbon monoxide alarm sounds, or if anyone has headaches, dizziness or nausea that improves when they leave the house.
Find your stopcock and turn it clockwise. It's usually under the kitchen sink, sometimes in a downstairs loo or utility. If you've never found it, go and look now while nothing is wrong — it takes two minutes and saves a ceiling.
If water is anywhere near electrics, turn the power off at the consumer unit before you go near it.
Every cold snap, thousands of boilers shut down for exactly this reason, and it's the easiest fix there is. If your boiler stopped overnight in freezing weather, and there's a gurgling from it, this is very likely why.
The condensate pipe is the white plastic pipe, usually 22mm, running from the boiler out through an external wall. When it freezes, the boiler can't drain and locks itself out as a safety measure.
If it keeps happening, the pipe is probably too narrow, too long, or badly routed. That's a permanent fix worth doing rather than thawing it every winter.
Ring straight away if: there's a baby, an elderly or unwell person in the house, temperatures are near freezing, or you also have a leak.
Worth checking first: is the boiler pressure between 1 and 1.5 bar on the gauge? Is the timer set correctly? Has anything tripped in the consumer unit? Is the gas on to other appliances? Has the condensate frozen, if it's cold out?
Those four cover a fair share of winter call-outs, and none of them require opening anything.
Pressure should sit between 1 and 1.5 bar when the heating is off. Losing pressure over days or weeks means water is escaping somewhere — a radiator valve, a joint, or the pressure relief pipe outside.
Topping it up occasionally is fine. Topping it up every week is not — you're masking a leak that's slowly damaging something.
The two dates worth never missing: your annual service, and your landlord gas certificates. Add them to your calendar here — nothing is sent anywhere, it just makes a calendar file your phone or computer opens.
Miss the annual service and most manufacturer warranties stop covering you. Set the reminder for a year after your last one.
A CP12 certificate lasts twelve months. Letting one lapse is a criminal offence, and it invalidates most landlord insurance. Add your properties and this will tell you what's coming due. Saved in this browser only.
What it actually costs to cook, wash and boil. Handy when deciding whether the air fryer really is cheaper than the oven — it usually is.
| Appliance | Typical use | Cost each time | If used daily, per year |
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Based on typical power ratings. Your own appliances will differ. Gas hobs and gas ovens are charged at your gas rate; everything else at your electricity rate.
Put every monthly bill in one place and see the annual total. Most people are surprised. Nothing here leaves your browser.
Honest ones. No "wear a jumper" nonsense — these are the things that actually move the number, in rough order of how much they save.
Most combi boilers leave the factory set at 70–80°C. Drop the heating flow to around 60°C and a condensing boiler starts actually condensing, which is where its efficiency comes from. Free, takes a minute, and your house still gets warm.
An unserviced boiler drifts out of tune and burns more gas for the same heat. It also invalidates most manufacturer warranties — so a £400 part becomes your problem instead of theirs.
Cold at the top, warm at the bottom means air in the system. You're paying to heat water that never reaches the room. Five minutes with a radiator key.
Heating the spare room to the same temperature as the lounge is money burnt. TRVs let each room settle at its own temperature.
Radiators cold in the middle usually means sludge in the system. A power flush restores circulation, and the boiler stops working harder to compensate.
A hot tap dripping once a second wastes a few hundred litres a month — and if it's the hot one, you paid to heat every drop.
Uninsulated pipework in a cold loft or garage sheds heat the whole time your heating runs. Pipe lagging is inexpensive and lasts decades.
Heating a home steadily to the temperature you want costs less than letting it go cold and firing everything at maximum to catch up.
We'll tell you what your boiler is costing you and whether replacing it is worth it — straight answer, no sales pitch. Established 1982, rated 10/10 across 303 Checkatrade reviews.