Electric Boilers | No Gas, No Flue, 100% Efficient

Not sure which type of electric boiler you need? Browse by category:

Electric Combi Boilers — Instant hot water and heating in one unit, no cylinder required

Electric System Boilers — Heating circuit boiler for use with a separate hot water cylinder, sealed pressurised systems

Electric Heat Only Boilers — For open-vented gravity-fed systems, ideal for like-for-like replacement of older regular boilers

Electric boilers work in exactly the same way as gas boilers — heating water and distributing it around your central heating circuit — but use electricity as the heat source instead of burning gas or oil. There is no flue, no combustion, no annual gas safety check, and no standing charge for a gas connection. They are 100% efficient at point of use, completely silent, and compatible with solar PV systems, allowing you to heat your home using energy you generate yourself. They are an increasingly popular choice for off-grid properties, new builds, flats, and any home moving away from fossil fuel heating.

However, not all electric boilers are the same — and choosing the wrong type for your system is one of the most common and costly mistakes buyers make. The three types work in fundamentally different ways and are suited to different installations. Understanding the differences before you buy will save you significant time and expense.

Electric Combi Boilers — Heating and Instant Hot Water in One Unit

An electric combi boiler provides both central heating and domestic hot water from a single wall-mounted unit, with no need for a separate hot water cylinder, cold water tank, or loft pipework. When you open a hot tap, the boiler switches to domestic hot water mode and heats the water as it flows through — delivering it on demand at mains pressure.

Combi boilers are compact, simple to install, and ideal for flats, smaller homes, and properties where space is limited. The key limitation to understand is flow rate — the amount of hot water the boiler can deliver is directly determined by its kW output. A 7kW combi boiler produces approximately 2.9 litres per minute of hot water, which is unlikely to satisfy a standard shower. A 14kW model produces around 5.7 litres per minute, which is generally considered the practical minimum for comfortable single-shower use. If you need to run multiple hot outlets simultaneously, a combi boiler will struggle regardless of output — in that case a system boiler with a cylinder is a better fit.

At 14kW single phase, a combi boiler draws approximately 63 amps and requires a dedicated 10mm² circuit. Higher outputs require a three-phase supply.

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Electric System Boilers — For Sealed Pressurised Systems with a Hot Water Cylinder

An electric system boiler heats your central heating circuit and, when paired with an indirect unvented cylinder, also heats your stored domestic hot water via a coil. Unlike a combi boiler, it does not produce hot water on demand — it relies on a cylinder to store pre-heated water ready for use. This means it can supply multiple bathrooms and outlets simultaneously without any drop in performance, making it the better choice for family homes with higher hot water demand.

System boilers work on sealed, pressurised systems — there are no cold water tanks in the loft, and the system is filled to a set pressure (typically 1–1.5 bar) directly from the mains. If you currently have loft tanks feeding your heating, you either need to convert to a sealed system at the same time, or opt for a heat only boiler instead.

A separate hot water cylinder is always required with a system boiler. If you want the boiler to heat both the radiators and the hot water, you need an indirect unvented cylinder. If you prefer the cylinder to heat itself independently using its own immersion heater, a direct unvented cylinder is the alternative.

Single phase models run from 4kW to 14.4kW. Outputs of 16kW and above require a three-phase 400V supply.

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Electric Heat Only Boilers — For Open-Vented Gravity-Fed Systems

A heat only electric boiler — also called a regular or conventional boiler — is designed for open-vented systems that use a small feed and expansion tank in the loft to maintain water level and accommodate expansion. It provides central heating only, and hot water is handled separately by your existing cylinder and immersion heater.

This is the correct choice when you are replacing an older regular gas or oil boiler on an existing open-vented system and want a straightforward like-for-like swap without converting the pipework. Attempting to fit a system boiler onto an open-vented circuit without converting it first is a common and expensive mistake — the two types are not interchangeable.

If you are unsure which type of system you have, check the loft. Two small cold water tanks feeding your heating and hot water circuit means you have an open-vented system and need a heat only boiler. A pressure gauge and filling loop with no loft tanks means you have a sealed system suited to a system boiler.

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Which Type Is Right for You? — Quick Summary

If you're still unsure which type suits your property and existing pipework, contact our team — we're happy to help you spec the right solution before you order.