When you're choosing water heaters, start with the job, not the label: mains pressure or stored, electric or gas, and how much room you've actually got for the unit. Point of use models suit short runs and small draw-off points. Larger vented or unvented options make more sense where demand is steadier. The usual mistake is buying on output alone, then finding the footprint or supply arrangement doesn't suit the site.
Heatrae Sadia Hotflo 10 Unvented Water Heater - 10L 2.2kW
10 litre unvented electric water heater for up to two commercial basins
Tesla Copper Immersion Heater and Thermostat TIH525 - 685.8mm
3 kW copper immersion heater 685.8mm, with dual safety thermostat, for soft wate…
Hyco Speedflow Under Sink Unvented Water Heater - 2kW 15L
Unvented water heater, 15L, 2kW, splashproof IPX4
Ariston Andris Lux Oversink Electric Water Heater - 15L 2kW
Ariston Andris Lux oversink electric water heater, 15L, 2kW, compact and unvente…
Heatrae Sadia Multipoint Eco Vertical Unvented Water Heater - 50L
50 litre vertical unvented water heater with digital controls and stainless stee…
Ariston Andris Lux Undersink - 15L 2kW EP15
15 litre unvented water heater with titanium enamelled tank and 2kW power
Triton Instaflow Undersink Stored Water Heater - 2kW 15L
2kW 15-litre undersink electric water heater, max 75°C
Haier Under Sink Electric Water Heater - 15L
15 litre under-sink electric storage water heater
Tesla Immersion Heater and Thermostat Dual Safety - 457mm
457 mm immersion heater and thermostat, dual safety
Immersion Heater - 14" 3kW
3kW immersion heater, 14-inch length, for Gledhill cylinders.
Start with the space you’ve actually got and how the unit will be used, because that usually rules out half the options before you get into finishes or extras. If the layout is tight, a compact unit saves grief on the install. If demand is steady, look at output and recovery rather than just the cheapest box on the shelf. Electric water heaters suit jobs where the supply is straightforward. Gas water heaters make more sense where you’ve already got the fuel and the spec calls for it. Commercial water heaters are a different conversation again. It’s more about duty and demand than footprint.
You’re usually choosing water heaters by how the job is fed and how fast the hot water needs to be there. Electric water heaters are the straightforward pick where the supply is simple and you want less to sort on the fuel side. Gas water heaters make more sense where gas is already in place and the demand justifies it.
Instant water heaters and instantaneous water heaters suit jobs that need hot water on demand without waiting on stored volume. The trade-off is less buffer if several outlets are drawing at once.
Point of use water heaters work best when you want the heater right at the draw-off. That keeps the run direct and avoids overspecifying the whole Central Heating setup.
If space is tight, compact water heaters are the first place to look. You get a smaller footprint, but you give up stored capacity. That matters when the outlet needs to run for longer than expected.
For straightforward replacements, check what is already there before you commit. If the rest of the kit needs changing, sort that at the same time. If you are picking up the extras as well, Central Heating Accessories usually covers the bits that get missed. Where the installation needs the right termination and fittings, Flues & Boiler Accessories is the other one to line up before you start.
Once you’ve picked the water heaters, the next call is what sits around them and what the room still needs to finish properly. That covers the surrounding finishes, any storage or screening the job needs, and the details that stop you going back later to tidy up.
A lot of call-backs come from the last 10% - awkward access, a finish that doesn’t match, or no allowance for maintenance. Keep the main unit choice in mind, then look at the adjacent plumbing and finishing items from the same central heating range so you’re not mixing parts that don’t suit the rest of the install.












