Boilers usually come down to what’s already in the property, how much hot water demand you’re dealing with, and whether you’re replacing like for like or changing the setup. Combi boilers suit tighter installs where you don’t want a cylinder taking space. System and regular boilers make more sense where stored hot water or existing pipework already points that way. Gas boilers are still the common call on many jobs, but electric boilers or oil boilers come into play when the fuel and supply situation rules the choice.
Vaillant Ecofit Pure 615 System Boiler - 15kW
15kW gas system boiler, compact and Quiet Mark-approved, ideal for small homes
Main ERP Compact Combi Eco Boiler - 25kW
Main Compact Combi Eco Boiler, 25kW output, ErP A rated
Worcester Bosch Greenstar 8000+ Combi Boiler - 32kW
32kW combi boiler with longest guarantee and easy installation features.
Vaillant Ecofit Pure 425H Boiler & Flue
Vaillant Ecofit Pure 425H boiler with flue
Vaillant Ecotec Pro 28kW ERP Combi Boiler Natural Gas
28kW natural gas combi boiler, tested with hydrogen blend, 2-year guarantee
Ideal Heating Esprit Eco2 Combi Boiler - 35kW
35 kW gas combi boiler with built-in timer and digital display, made in UK
Glow-Worm Energy7 18S System Boiler
High-efficiency gas system boiler with compact design and 7-year guarantee.
Glow-Worm Compact LPG Combi Boiler - 28kW
Compact 28kW LPG combi boiler, cupboard fit
Glow-Worm Energy 18R 18kW Heat Only Boiler with Horizontal Flue Pack
18kW heat only boiler with horizontal flue pack and aluminium heat exchanger
Vaillant Ecotec Plus 400 Heat Only Boiler - 24kW
24kW gas heat only boiler, high efficiency, 7-year guarantee
Start with the space you’ve actually got and how the job needs to work, then the rest of the choice gets a lot clearer. On a tight swap, a compact combi is often the cleanest answer. If the property already relies on stored hot water, a system or regular setup usually keeps the spec closer to what’s there. Fuel and site conditions still matter - gas, electric and oil boilers each change the call. Layout comes first, because that’s where the wrong choice usually causes grief at install.
Combi boilers are the usual pick when you want one unit doing the lot and you are not building around a cylinder. They are quick to place, but they rely more on the incoming supply, so they are not the answer everywhere.
System boilers make more sense when the cylinder is staying in the job and hot water demand is steadier. Regular boilers still fit where the existing setup is already built around stored water and older pipework.
Electric boilers suit sites where gas is not an option, but running cost and electrical capacity usually decide that one quickly.
Most of the choice comes down to this. Keep the existing layout, or change it and take on the extra work. For the wider Central Heating range, that is the first split that matters.
You’re usually choosing boilers on three things: what’s already in the property, what fuel you’re tied to, and how much room you’ve got for the rest of the kit. A combi keeps the setup lean where you do not want cylinders or tanks in the way. System and regular boilers make more sense when the existing layout already depends on stored hot water.
Electric boilers can suit sites without a gas or oil supply, but they are not the answer where demand is high. If you are pricing the job properly, do not forget the extras - Central Heating Accessories and Flues & Boiler Accessories are often what decides whether the swap is straightforward or turns into a return visit.
Once the boiler’s chosen, the next decisions are the parts around it that keep the job moving. Check the flue run first, then sort the controls and any boiler accessories before you leave the counter. That’s where delays usually start.
If you’re tidying the install at the same time, central heating accessories and finish items matter more than they look. On replacement boilers, check what’s already on site first. That shows what needs changing and what can stay.







