Domestic micro-CHP unit finally comes to market

The first combined heat and power unit suitable for domestic properties will be commercially available in April.

Boiler maker Baxi will launch the UK’s first domestic combined heat and power (CHP) unit in April, after a decade of development.

Micro-CHP units are similar in size to conventional boilers, but generate electricity along with heat so they have the potential to substantially reduce a home’s carbon emissions. Most units are based on Stirling engines powered by natural gas.

Companies including Baxi and New Zealand-based WhisperGen have been developing units for over a decade. Units were expected to be commercially available by 2002 (ENDS Report 301, p 27). However, launch dates have repeatedly been put back (ENDS Reports 330, pp 33-34).

In 2007, BG Group closed its micro-CHP arm, Microgen, because it could not reduce production costs to a viable level (ENDS Report 386, p 13).

Baxi’s Ecogen unit is manufactured in Preston and it will be available direct from the company and through British Gas.

The unit is capable of providing 1.1 kilowatts electrical output and 24kW heat, according to Sarah Brook, the company’s marketing director. She says it is suitable for homes with a heat load above 20,000 kilowatt hours a year: properties with at least three bedrooms and older homes that cannot be easily insulated. This category includes a third to a half of the UK’s housing stock, according to the Carbon Trust.

The company expects most units to be sold to housing associations or housing developers looking to improve their energy efficiency ratings.

Baxi says the units have 23% lower carbon emissions than condensing boilers. This is much higher than the 7.5% savings achieved in Carbon Trust trials of micro-CHP units (ENDS Report 395, p 14). However, the Carbon Trust has not tested Baxi units.

Ms Brook would not say how much units will cost, saying it depends on installation. But Baxi is calling for 15p per kWh support under the government’s "clean energy cashback" scheme (ENDS Report 414, pp 42-43). This starts in April and establishes a series of feed-in tariffs for microrenewables up to 5MW size and gas-fired micro-CHP units up to 50kW.

However, the energy and climate department (DECC) has yet to reveal the support level for micro-CHP.

In January, the MicroPower Council, Combined Heat and Power Association and Heating and Hot Water Industry Council wrote to energy minister Lord Hunt urging him to announce the level for micro-CHP. Indecision was "threatening the future of 20,000 UK jobs and an industry with a potential value to the UK economy of £1.5bn," they said.

Baxi says that in its trials individual homes generated 1,800 kWh per year on average and exported at least 270kWh to the grid. A 15p/kWh payment would mean homeowners would receive £270 a year plus a 5p bonus for every kilowatt hour of electricity exported. If the unit cost £1,500 more than a condensing boiler, the pay back time would be about five years.

Other micro-CHP developers are pushing ahead with their own plans. WhisperGen has formed a joint venture with Spanish energy company Mondragon, which is called Efficient Home Energy. In August it began "low-level" manufacturing 3,000-5,000 units of its device per year in Spain. Eon is trialling the unit in the UK.

Ceres Power is also pushing ahead with a 1kW fuel cell unit due to launch by the end of 2011. In December it started to manufacture fuel cells in Horsham, West Sussex, which will be fitted into boilers made by Dutch firm Daalderop BV.

British Gas has made a commitment to buying 37,500 units over four years subject to successful trials.

Ceramic Fuel cells is developing a 2kW model focusing on electricity production and only providing heat for hot water. It says these are suitable for new build homes with lower space-heating needs. This will launch by 2011.