Combi, System or Regular Boiler?

Choosing a new boiler, or even understanding the one you already have, can feel confusing if you’re not sure which type is installed in your home. The good news is that identifying your boiler type is actually very simple once you know what to look for. In this guide, we’ll break down the three main boiler types in the UK: combi, system, and regular, and show you exactly how to tell which one you have.

Combi boiler (Combination boiler)

A combi boiler is the most common type in modern UK homes. It provides heating and hot water directly from the boiler, without the need for any tanks or cylinders.

If you have a combi boiler then

Look for these signs:

• No hot‑water cylinder in the airing cupboard

• No cold‑water tank in the loft

• You get instant hot water when you turn on the tap

• The boiler is usually a single compact unit in the kitchen, cupboard or utility room

Who usually has one?

Flats, small to medium homes, and properties.

System boiler

A system boiler works with a hot‑water cylinder, but doesn’t need a loft tank. It heats water and stores it in the cylinder for later use.

If you have a system boiler then

Check for:

• A hot water cylinder (usually in an airing cupboard)

• No cold water tank in the loft

• The boiler itself is a single unit, but your hot water is stored, not instant

• You may run out of hot water if the cylinder empties

Who usually has one?

Medium to large homes, especially those with two or more bathrooms.

Regular boiler (Traditional boiler)

A regular boiler is the traditional setup found in older homes. It uses both a hot water cylinder and a cold water tank in the loft.

If you have a regular boiler then

Look for:

• A hot water cylinder in the airing cupboard

• A cold water storage tank in the loft

• Sometimes a second smaller feed and expansion tank

• The boiler is usually larger and part of a multi‑component system

Who usually has one?

Older properties, homes with gravity‑fed systems, or houses with low mains pressure.

Why it matters

Knowing your boiler type helps you:

• Choose the right replacement

• Understand installation costs

• Pick the correct size (kW)

• Avoid buying a boiler that won’t suit your home

If you’re planning a replacement, your current setup is usually the easiest and cheapest type to stick with — but upgrading is always possible.