Electric System Boilers | Heating Only — Requires a Separate Hot Water Cylinder

About

An electric system boilers heats water and circulates it around your central heating circuit — radiators, underfloor heating, or both. Unlike a combi boiler, it does not produce domestic hot water directly from the tap. It works in conjunction with a separate hot water cylinder (either a direct unvented cylinder with its own immersion heater, or an indirect unvented cylinder heated by the boiler itself via a coil). This is an important distinction that catches many buyers out — if you want instant hot water from a single unit with no cylinder, you want an electric combi boiler instead. System Boiler vs Combi Boiler — Which Do You Need? The right choice depends on your hot water demand and available space. A combi boiler heats water on demand as it flows through the unit, making it compact and simple — but the flow rate is limited by the boiler's kW output, and it struggles to supply multiple outlets simultaneously. A system boiler with a cylinder stores a larger volume of pre-heated water, meaning you can run multiple showers, baths, and taps at the same time without a drop in performance. For family homes with two or more bathrooms, or any property with higher hot water demand, a system boiler and cylinder combination is almost always the better choice. What Does a System Boiler Actually Do? The system boiler's job is to heat the central heating circuit and, if paired with an indirect cylinder, to also heat the stored hot water via a coil inside the cylinder. The boiler itself contains a pump, an expansion vessel, and the heating element — meaning the installation is relatively clean, with fewer components needed in the airing cupboard or plant room compared to an older open-vented system. All of the boilers in this range are sealed system (pressurised) units, which means they work with modern unvented cylinders at mains pressure. ⚠️ You Will Need a Cylinder — This Is Not Optional A system boiler cannot store or deliver domestic hot water on its own. Every installa