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 Ecotec Plus 620 System Boiler - 20kW
20kW gas system boiler, LPG convertible, 5-year guarantee
Strom Single Phase Electric System Boiler - 14.4kW
Strom 14.4kW single phase electric system boiler, no flue required, white
Vaillant Ecotec Pro 28 28kW Combi Boiler with Vertical Flue Pack
ErP A rated 28kW combi boiler with vertical flue pack, up to 94% efficiency
Baxi 430 Combi 21 Boiler with Vertical Flue & Filter - 30kW
30kW Baxi 430 Combi boiler with vertical flue and filter
Glow-Worm Micracom Combi Boiler with Horizontal Flue - 28kW
Glow-worm's smallest 28kW combi boiler with horizontal flue
Navien NCB300 Combi Boiler & Horizontal Flue - 28kW
28kW gas condensing combi boiler with horizontal flue and LCD control panel
Vaillant Ecotec Commercial Boiler - 64 kW
64 kW commercial boiler with compact design and accessible panels
Vaillant EcoTec Plus 630 30kW System Boiler Only - Power
Vaillant 30kW system boiler with smart home connectivity
Vaillant Ecotec Plus 836 36kW Combi Boiler with Horizontal Flue & Boiler Protect…
Vaillant Ecotec Plus 836 combi boiler, 36kW, with horizontal flue and protection…
Ideal Heating Esprit Eco2 30kW Combi Boiler
Ideal Esprit Eco2 30kW combi, 5-year warranty
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.







