Not sure whether your boiler is condensing or not? You’re not alone.
Since April 2005, virtually every new gas boiler installed in the UK has had to be condensing by law (oil boilers since 2007).
But if your boiler predates those rules - or you simply don’t know when it was fitted - it can be tricky to tell.
This guide explains what a condensing boiler is, how to identify one, and why upgrading from an older non-condensing unit is almost always a smart move.
Let’s dive in!
PS - we fit new combi boilers with gas safe installation nationwide. Simply answer these questions, get your fixed price and you could get it installed as quick as tomorrow.
What is a Condensing Boiler?
A condensing boiler recycles the hot gases created when it burns fuel.
Instead of letting that heat escape through the flue, it captures and reuses it to pre-warm the cold water coming in.
That clever trick means:
Higher efficiency – usually 90%+ (compared with 60–70% for old non-condensing models).
Lower carbon emissions – good for your wallet and the planet.
Lower bills – less fuel wasted, more heat for your money.
Condensing boilers can run on either gas or oil and are now by far the standard in UK homes.
How Can I Tell If I Have a Condensing Boiler?
[1] Check the installation date
Gas boilers installed after April 2005 (or oil boilers after April 2007) are, by law, condensing.
If yours was fitted earlier, it might still be condensing (some were available pre-2005), but non-condensing is more likely.
[2] Look for a condensate pipe
Condensing boilers produce condensation as a by-product.
You’ll usually see a white plastic pipe leading from the boiler to a household drain. If you’ve got one, it’s almost certainly condensing.
[3] Inspect the flue
A condensing boiler flue often has visible steam coming out in cold weather.
If the flue is an old single-skin metal pipe, that points towards non-condensing.
[4] Check the manual or model number
The quickest way to be sure is to check your boiler’s paperwork.
If you don’t have it, note the make/model and call the manufacturer - they’ll tell you whether it’s condensing.
[5] Ask a professional
Still unsure? A Gas Safe engineer can confirm in minutes.
Why Upgrade to a Condensing Boiler?
If you discover your boiler is non-condensing, it’s likely 15–20 years old. At that age, even if it’s still working, it’s:
Far less efficient – wasting up to a third of the fuel you’re paying for.
Less safe – older appliances don’t have today’s built-in safety features.
Unreliable – breakdowns become more common (and costly).
💡 Replacing a non-condensing boiler with a modern A-rated condensing model could save you around £300+ a year on bills, according to Energy Saving Trust.
Bottom Line
If your boiler was fitted after 2005, relax - it’s almost certainly condensing. If it’s older, look for a condensate pipe, check for steam at the flue, or confirm with a pro.
Either way, if you’re still running a non-condensing boiler, now’s the time to upgrade. It’ll save you money, cut your carbon footprint, and keep your home safer and warmer.
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If you’re aiming to get the best deal on a new boiler, consider getting a quote from us, here’s why:
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