As the provider of heating and hot water throughout the year, a central heating boiler is a vital component of every home. Getting a new model, or replacing an old one, can be expensive, and the choice you make will have an effect on your home’s energy efficiency, and consequently its bills, throughout the life of the boiler. Here is an introduction to the various types of boiler available, the fuel options and the technologies involved. For advice on the amount you can expect to spend, read our guide on new boiler costs.
Types of Central Heating Boilers
There are a few types of central heating boilers on the market, although your choice may be limited depending on the size of your home, how much hot water you need and the kind of fuel you have access to. Most homes use gas supply boilers, and this type is generally considered the most cost-effective. If your home is not attached to the gas mains supply, there are other options available to you (see below).
If your existing boiler is very old, it is likely that it is not very energy efficient. Nearly all modern boilers, regardless of type, are ‘condensing’ models. This means that they work more efficiently by re-using heat that would otherwise have been wasted. These are the three main types of condensing boiler:
This is the standard type of boiler, and the most common amongst older models. It is a gas boiler that heats up water and supplies it to the radiators and a separate hot water cylinder, where the hot water is stored for later use in the kitchen and bathroom. The initial cold water is supplied from a cistern – usually in the loft. A condensing heat-only boiler is the most efficient type for producing hot water, but some heat loss occurs during storage. If you are getting a new heat-only boiler, remember you will need space to store the hot water cylinder as well. Generally, these boilers are better suited to larger properties.
The most popular type of modern boilers, ‘combi’ boilers are ideal for flats and smaller houses. They can provide heat and hot water simultaneously, and on demand. Water is heated only as it is needed: when you turn on a tap, the water is drawn from the mains and heated in the boiler. This means that there is no need for a cylinder to store the hot water. One downside of a combi boiler is that they can only provide hot water to one tap at a time. If you have a large home with lots of people, it may be better to use either a heat-only or system boiler.
These work well with large houses which have a high demand for hot water. Similar to a heat-only boiler, system boilers use a cylinder to store the hot water. The main difference between the two types is that system boilers do not need a feed and expansion tank in the loft. So if you were thinking about doing something else with your loft, this could be the ideal option. Remember, with both system and heat-only boilers, you need to keep the cylinder very well insulated so as minimise heat loss and not waste energy.
Types of fuel for Central Heating Boilers
Most homes use gas to fuel their boilers. Apart from wood-burning (biomass) boilers it is the most energy efficient type, with a new condensing gas boiler operating with an energy efficiency of 89%, providing an average annual saving of around £300.
These work in a similar way to gas boilers, and are a necessary option for the millions of UK homeowners who are not currently connected to the main gas supply. With an oil burning boiler, you will need to get the oil delivered and then store it in a tank. Overall, the costs involved can be as much as twice the amount for gas.
This is a relatively new type of boiler, which is a good alternative to oil for anyone not connected to the main gas supply. They work by using electricity to heat elements in the boiler which then heat the water. They are easy to install, and much cheaper to buy than an oil boiler. One thing to remember is that it will mean a significant increase to your electricity bill and in the event of a power cut you will not have any hot water.
This carbon-neutral means of heating a home and providing hot water uses pellets, or chips, which are usually wood. They can be fed automatically and, although expensive to install, as a renewable energy source, a grant from the government’s Renewable Heat Incentive scheme is available. Visit the Renewable Energy section for more information on biomass and other renewable energy technologies and financial incentives.