Domestic CHP

Even though combined Heat and Power Boilers (CHP) have been in use for many years in larger scale units such as hospitals and schools, within a domestic setting they provide a fairly new option. Like other boilers, they provide efficient gas central heating and hot water, but they are also able to generate electricity which can be used throughout the home.

In turn, this allows for the reduction in fuel bills in addition to payments sourced through the Feed In Tariff scheme. They are therefore not only a more environmentally friendly option than old traditional boilers, but a more economic one too.

How Do CHP Boilers Work?

CHP boilers work to provide central heating and hot water the same as any other gas boilers, but a CHP boiler also contains a combustion engine. The first CHP boilers to go on sale in 2010 contained Stirling engines and were manufactured by Ecogen.

The combustion engine is heated by the burning gas when the boiler is started and this causes the helium within the engine to expand, which in turn forces a piston up and down between a copper coil, generating up to 1KW of electricity in the process.

Because the Stirling engine is in a sealed unit, it can use helium gas to move the piston instead of air. Helium has better heat transfer properties, making it a good choice and because these boilers have a sealed for life guarantee, required maintenance is minimal. However, the engine must be well engineered and manufactured to ensure its reliability.

The Ecogen boiler contains a built in energy meter allowing the user to see the amount of electricity which is being produced and has many controls to allow homeowners to regulate the temperature of rooms and hot water, which means more cost efficient heating.

Unfortunately, the main limitation with these boilers is that they only produce a small amount of electricity relative to the amount of heat they produce and so are mainly designed to be used when heat is required. Therefore, electricity will only be generated on days when the central heating is on.

Micro-CHP Boilers Currently Available

The most common type of micro-CHP boiler is the internal combustion engine model. Interestingly, these are often lorry diesel engines which have been adapted to run on mains gas and are connected to an electricity generator. This type of boiler has the highest ratio of heat to electricity production of all micro-CHP units. However, due to their large size and the fact they are quite noisy, they are not normally sold to domestic properties.

The Stirling engine micro-CHP is the most common type model that can be installed into domestic households. The units are smaller and quieter than the internal combustion models but produce less electricity.

Fuel cell CHP boilers are the newest kind of model on the market and are only just being introduced to the United Kingdom. These boilers take the energy from fuels at the chemical stage rather than through the process of burning it. As it is such a new technology, it is not yet available to UK homeowners although it is hoped it will come onto the market within the new few years.

Best Buys

Baxi Boilers

The highly praised Baxi, as well as being in business since 1866, claim to be at the forefront of CHP boiler systems, supplying not only to homes but also to small commercial businesses. The Baxi Ecogen is an MCS accredited model which won the 2010 Green Innovation Award. Price will be dependent on requirements, however British Gas currently have an incredible spring sale up and running, though you'd better be quick as it does end on 30th June 2012.

You can claim up to £400 scrappage discount on your old boiler when purchasing a Baxi boiler and they even give you a one year subscription to HomeCare 200 - boiler cover worth £204.

Vital Energi

Vital Energi are one of the leading innovators within the energy efficiency sector. They provide a full service from start to finish; offering advice, making recommendations and design ideas, installing your boiler and providing maintenance and advice on payment/meter schemes if required.

Their CHP boiler design can be incorporated into a tri-generation scheme which can also provide a cooling system by cooling the excess heat to produce chilled water - effective even within a large air conditioning system.

There are numerous suppliers and various systems that fall into the CHP category. However, it is difficult to gain an idea of price until your home is actually assessed for requirements. They don't exactly come cheap - but they are a wonderful investment.

Be sure to find out if you are entitled to any money from the government. You will be looking to pay somewhere between £3,000 and £8,000 for a good domestic system, depending on the size of your home. Make sure you compare all suppliers to secure the best deal.

What Are The Costs and Benefits of CHP Boilers?

CHP boilers are not a cheap option. Costing around £5000, they are roughly double the price of a traditional combination boiler, although this depends on the size of the home. (Obviously, larger homes need larger boilers.) They can, however, save up to £500 annually on fuel bills which means that the extra cost of a CHP boiler compared to an ordinary boiler would be paid off in five years.

Any unused electricity can also be sold back to the energy supplier via the Feed in Tariff scheme, where the homeowner is paid a certain amount per kW of electricity fed to the National Grid.

They also benefit the environment because the electricity generated is used on-site rather than being produced in a power station. They are therefore more energy efficient and less carbon dioxide is created. Over its lifetime, a CHP boiler will produce 0.8 tonnes less carbon dioxide that the most energy efficient combination boilers.

In Brief

Domestic micro-CHP boilers are a new technology which aims to produce both heat and electricity which can be used around the home. They are seen as more environmentally friendly because they produce two different types of energy off one source. Currently these boilers run off mains gas but they should be able to run off biofuels in the future which will reduce their carbon footprint even further.

There are 3 different types of micro-CHP boiler in production but the Stirling engine is the only real current option for domestic households. Such boilers can earn their owner £500 a year in Feed In Tariff payments as well as around £60 a year in electricity bills.