By Boiler Quotes Editorial Team · Updated 20 July 2026
Why Efficiency Is No Longer the Deciding Factor
A decade ago, choosing between boilers meant comparing efficiency figures. That argument is largely settled. Regulations require new gas boilers sold in the UK to meet a high minimum efficiency, so mainstream condensing models now cluster in a narrow band of roughly 92 to 94 percent.
A difference of one percentage point between two boilers is worth very little on your annual bill. What separates brands in practice is what happens over the following ten years: whether the warranty holds up, whether parts are available quickly when something fails, and whether the hot water performance suits your household.
The Five Things Worth Comparing
1. Warranty Length and Conditions
Warranties on UK gas boilers commonly run from 2 to 12 years. The headline number is only half the story. Check what you must do to keep it valid, which almost always includes registering the boiler within a set period after installation and having it serviced annually by a qualified engineer. Some manufacturers only offer their longest warranties when the boiler is fitted by an installer on their accredited scheme.
2. Parts Availability
When a boiler fails in February, what matters is whether a local merchant has the part on the shelf. Widely fitted brands tend to have better parts coverage across the country, which shortens repair times and keeps repair costs competitive because more engineers are familiar with the appliance.
3. Hot Water Performance
For a combi, look at the flow rate in litres per minute at a given temperature rise, not just the kW figure. This is the number that decides whether your shower feels strong. Two boilers with the same kW rating can perform differently here.
4. Physical Size and Serviceability
A compact boiler that fits in a kitchen cupboard is genuinely useful, and clearance requirements around it affect where it can go. Ask how easy the appliance is to service, since awkward internal layouts add labour time to every future visit.
5. Controls and Compatibility
Most manufacturers now offer their own smart control. Check whether the boiler works with third-party controls you might prefer, and whether features such as weather compensation or load compensation are supported, since these genuinely reduce running costs.
Tiers Rather Than League Tables
Rather than ranking brands, it is more useful to think about tiers, because most manufacturers sell across several of them.
| Tier | Typical appliance price | What you generally get |
|---|---|---|
| Entry | £600 - £900 | Solid efficiency, shorter warranty, basic controls |
| Mid | £900 - £1,400 | Better hot water flow, 7 to 10 year warranty, smart control options |
| Premium | £1,400+ | Stainless steel heat exchangers, quieter running, longest warranties |
The Installer Matters More Than the Badge
This is the part most brand comparisons skip. A mid-range boiler correctly sized, fitted on a properly flushed system with a filter and commissioned carefully will outlast a premium boiler installed badly. Most boiler problems in the first few years trace back to installation and system condition rather than to the appliance.
So when you are comparing quotes, give real weight to how thorough the installer was at survey stage. Did they measure your mains flow? Did they ask about your hot water habits? Did they explain why they recommended that output? Those questions predict your experience better than the name on the front panel.
Questions to Ask Before You Choose
- What is the warranty length, and what exactly must I do to keep it valid?
- Is the longest warranty available through you, or does it require an accredited installer?
- What flow rate in litres per minute will I get at the shower?
- How available are parts for this model locally?
- What does an annual service cost, and do you offer one?
- Is this appliance compatible with the controls I want to use?
A Sensible Way to Decide
Shortlist on warranty and hot water performance, sanity-check parts availability, then choose between the remaining options on fitted price. Ask each of your installers what they would fit in their own home and why. Experienced engineers have strong, well-founded views based on what they repair most often, and that is information you cannot get from a brochure.
Want quotes with the appliance, output and warranty clearly stated? Compare free, no-obligation quotes from up to 3 Gas Safe registered installers using the form below.
