DOMESTIC ENERGY OPTIMISATION AND THE MARKET DEVELOPMENTS FOR MICRO-CHP Simon Burton, FaberMaunsell Ltd.

1. INTRODUCTION In1998 a project was set up by Gasunie and GERG, the European Gas Research Group, to investigate and demonstrate the potential for optimisation of energy use in dwellings by the use of newly developed gas systems and appliances, in conjunction with renewable energy sources. The three year “Domestic Energy Optimisation” project (DEO) received grant funding from the European Commission and was completed at the end of 2002. It was coordinated by ECD Energy and Environment, now FaberMaunsell Ltd, and had as contracting partners Gasunie (Netherlands), Gas de France, Advantica (UK), Italgas and AGEC (Italy). The project consisted of test sites in UK (2), France (2), Netherlands (2) and Italy (2). Two “Whispergen” stirling engine microCHP systems were installed and monitored in France and the Netherlands. Other energy saving systems were also installed and monitored including solar heating systems in France, the Netherlands and UK, a ground sourced heat pump in the Netherlands, a Yamaha gas fired heat pump in Italy, efficient gas appliances in the Netherlands and hot-fill dishwashers in Italy. A parallel project MICROMAP in 2001/2, supported under the European Commission SAVE programme, examined the overall context for the development of microCHP throughout Europe, and the results of this work will also be discussed in this paper. The project was coordinated by FaberMaunsell Ltd with partners the European Association for the Promotion of Cogeneration (COGEN Europe), Energy for Sustainable Development Ltd (ESD) UK, EA Technology Ltd UK, European Gas Research Group (GERG), SIGMA Elektroteknisk AS Norway, and Enervac- Flutec Ltd Greece.

2. MICRO-CHP IN THE EUROPEAN CONTEXT There is considerable interest in Europe in microCHP from the European Commission, National Governments, the energy supply industry and the private sector. With the large number of individual houses in many European countries, the potential for home based electricity generation with use of the heat for space and water heating is enormous. Several stirling engine based systems are being developed and tested and a start is being made on fuel cell based systems. Deregulation of the electricity supply industry, and forthcoming legislation will enable homeowners to export electricity to their local grid and the development of suitable control systems is well advanced. The European Commission and National Governments are keen to encourage all initiatives which can contribute towards greater energy efficiency and thus various incentives are likely to be made available, if and when the technology has been demonstrated to be efficient and effective in reducing overall CO2 emissions. There is considerable variation in the heating demand of dwellings in Europe, both between north and south and between different types and ages of buildings. For energy efficient operation, any CHP system must be sized according to the heat demand and thus the variation in the European housing stock gives the opportunity to use many different types and sizes of microCHP. In warmer southern regions, it is theoretically possible to use heat driven chillers run from microCHP systems, to provide necessary cooling in summer, and thus extend the working time of the systems, though much more development in the chiller technology is necessary before this can be realised. There are currently many barriers to the widespread use of microCHP systems in European homes. The technologies are not adequately developed and tested; the legal and regulatory frameworks are not in place; and adequate finance, delivery, installation and maintenance systems are not available. These issues will be expanded upon later in this paper.

3. THE GAS HEAT PUMP DEMONSTRATIONS A Nefit diffusion absorption heat pump, 3.6 kW base load was install and tested in the Netherlands, in conjunction with the 24 kW peak load additional high efficiency boiler. The external heat source was a vertical ground heat exchanger comprising 40 m deep coaxial piping. The ground source was designed to produce about 1kW of the necessary heat. Together with the high efficiency boiler, a total efficiency increase of 20 % to 30 % was expected. Over an eight-month period in total 7.715 kWh of heat was produced from the heat pump central heating boiler combination with an efficiency of 82%. In total 5% of it was produced by the heat pump over the period it was in operation. The contribution from the heat pump is thus disappointing and was probably due partly to a faulty heat pump heat exchanger. The manufacturer Nefit-Buderus explained the disappointing results as due to a combination of poor control system, non-operation of the system at night and interference caused by the gas boiler coming in to provide higher temperatures. With a better managed system a 20% contribution over the year should be possible. The average soil temperature at one metre depth followed the outside temperature, while the temperature at 30 metres stayed at 10 ºC except for half the month August and almost the whole month September. So there was no influence on soil temperature at 10 m depth from the heat extraction of the heat pump and only a slight influence from the cooling. In Italy a gas heat pump system was tested, a Yamaha GHP 3 HP model made in Japan, for supplying both heating and cooling in the demonstration house. The machine is driven by a endothermic gas-engine and is designed as an external unit including the engine itself, the compressor and the condensing unit, plus internal units, an evaporator and the airtreatment block. The engine can run at variable-load, depending on the heating/cooling needs of the internal units. The external temperature operation range allowed is -10 °C to 43 °C. R22 is used as the refrigerant. The GHP showed good performance for the whole period, though in the two seasons considered there were no particularly extreme weather conditions. The energy consumption can be considered quite satisfactory as far as the good comfort level is considered 20°C indoor temperature in winter and 25°C in summer, all day long

4. SOLAR HEATING DEMONSTRATIONS The results of the combined solar and gas water heating systems in the UK demonstrate the low levels of solar radiation in the average year. In a modern test house with three square metres of solar collectors on both east and west slopes of the roof, the gas consumption for domestic hot water was reduced by 26% and the overall gas consumption for space and water heating by 14%. Thus the solar energy contribution in an average year was estimated at 2420kWh. In a late 19th century terraced house with a single solar collector of four square metres on the south facing roof, solar heating supplied 25% of the water heating, 770kWh in a typical year. In France, close to Paris, an active solar water heating system, consisting of enclosed panels with a total surface area of 15 m2, was installed on the south-facing wall of the Test Pavilion. This was connected to a large hot water storage tank which can be supplied simultaneously by the solar water heating system and the conventional natural gas-fired boiler. Additionally, underfloor space heaters can be supplied by either system separately. Operation of these combined systems between March and October 2002, inclusively, reduced natural gas consumption by 3,564 kWh. The overall annual saving in space and domestic water saving was 21%. In the Netherlands, the solar panels, which were an integrated part of the heating systems, performed well bearing in mind the Dutch weather conditions. The four square metre South West facing system produced in total 1108 kWh over the period from and the two square metre South facing system, 860 kWh.

5. MICROCHP STIRLING ENGINE PERFORMANCE RESULTS The WhisperGen micro combined heat and power engine with an generator for 230 volt alternating current is built by Whispertech New Zealand. It is designed to provide both heat and power for an urban home, replacing the conventional central heating boiler and supplementing the grid supplied electricity. It is not designed to replace the electricity grid, but

rather to be used in conjunction with it. Future systems will incorporate the ability for off-grid running in emergency situations. Although using the same stirling engine system, Whispergen, the results at the two test sites were very different. In the Netherlands the performance was disappointing since it had incurable start up problems. The operation mode was set to a window of 7:00 o’clock in the morning until 11:00 at night. By stopping the engine at night complaints about noise by neighbours was prevented. During operation hours the engine actually worked for only a few hours a day. During the summer months when the engine worked well, there was not enough heat being used in the house to run for a longer time. A total of only 278 kWh of electricity was produced by the Stirling engine, while 4665 kWh of electricity was bought from the grid. Thus in total the Stirling engine produced less than 6% of the electricity used in the house. However, from earlier laboratory test it was established that under the given conditions the Stirling engine could have produced electricity and heat with an overall efficiency of 80 – 85 % (based on the upper calorific value) depending on the running time. In France, the operation of the microCHP system was much more successful, without significant operating difficulties. The natural gas-fired micro combined heat and power unit, with a rated electrical output of 0.75 kW and a rated thermal output of 5.00 to 6.00 kW provided all space and water heating, and electricity requirements in the Paris Test Apartment. Two configurations, with and without hot water storage, were tested. It was concluded that both configurations covered the heating needs of the apartment. Test results indicated an annual average global efficiency of 82% for the system, with thermal and electrical efficiencies of 75% and 7%, respectively. The annual savings compared with a conventional gas boiler system, show a delivered energy saving of 6% and a primary energy saving of 13%, overall.

6. EFFICIENT GAS EQUIPMENT DEMONSTRATION In addition to the microCHP unit and the ground sourced heat pump, the following equipment was installed and tested in the Dutch houses: • Climate control and remote controlled thermostat system, Hometronic by Honeywell BV • Gas flow measuring equipment with electronic remote reading, Elster G6 type Euro trace. • Electricity meter with remote reading • Synthetic gas lines, flexible synthetic gas piping PE-X DN 20, including thermal safety valves Wirsbo KE 171, and flow restrictions metik maxitrol KW38 GS15AV1OJXX. • Quick snap gas connectors, manufacturer KZ. installed for the barbecue and the separate cook top • Gas ceramic cook top and oven, Oranier computer controlled gas oven cook top combination 2195HB. • Separate Gas cook top with quick connector, 2 burners 1.5 kW, installed in one house only connected to the quick snap gas connector as a demonstration of an easy and flexible gas appliance. • Gas tumble dryer, Miele Novotronic T478G • Hot fill dishwasher. • Hot fill washing machine, Miele washing machine W979 Allwater (Hydromatic), • High efficiency boiler combined with solar heat collector and storage, Daalderop Multi Solar 22kW. • Remote controlled thermostatic radiator valves, Honey well Hometronic system. • Gas hearth in living room, Faber type Silva Gas hearth modulating by remote control. max 5kW (ref 7). • Local gas heater in summerhouse, 3 kW local heater of Robur is installed to demonstrate the usefulness of local gas heating instead of local electric heating. • A gas-fired barbecue, with a connector for the quick connection sockets which are fitted in the garden. The off-the-shelf equipment like gas tumbler dryer, hot fill washing machine and dishwasher performed flawlessly. The ceramic cook top worked fine, apart from one electronic failure which was repaired within a few days in cooperation with the Dutch import office. The Hometronic heat control system of Honeywell did work, but was thought to have too many disadvantages to be very suitable for households, though may be of interest for

small offices. The control panel proved to be too complicated to be handled properly by the occupants and backup and support in case of changing the built-in program is limited and expensive. The gas tumble dryers were a great success mainly because of the speed of drying cloth. Unfortunately they have been too expensive so far to be a success on the market. The ceramic cook top and gas oven were considered to work well. In Italy, tests were run on six different dishwashers to examine the use of gas heated hot water to replace the normal electric heating. Different types and lengths of connection pipes were tested, and different water temperatures. The tests showed that using gas preheated water for dishwashers is more efficient than using internal heating only when the water supply pipe from the boiler was no more than about 6 metres. A significant advantage however was that wash times were reduced by up to 40%. The cleaning quality was not affected by the use of hot water fill.

7. MICRO-CHP ASSESSMENT AND DEVELOPMENT PLAN 7.1 Study methodology The MICROMAP study, which ran from April 2001 to April 2002, had the objectives: to evaluate the technologies, markets and players; to assess grid connection and electricity payment issues; to estimate the possible system take-up in different countries up to 2020; to assess potential energy, CO2 emission reductions and cost savings; and to propose possible routes by which the new technology could be exploited. The project team brought together experts from the cogeneration, electricity, gas, housing, renewable energies and small generation industries, as well as experience in the coordination, planning and forecasting functions. The study covered the 15 EU countries plus Norway, with 11 Central and Eastern European (CEE) countries treated as a block in less detail. Existing sources of information were analysed to assess the current products availability, the potential in the existing and future housing stock, the current status of deregulation in the European energy markets and grid access for small generators, and possible delivery routes. The likely methods of market development and the possible rates of take up and consequent impact on European energy savings and CO2 emission reductions, were finally assessed. 7.2 Product development and availability Technologies most likely to be successful are Stirling engines within the next 2-3 years, followed by fuel cells within a 10 year timeframe. Quite apart from the prime mover technology, the status and market approach of the product developers is of key significance; the following summarises the key players active in Europe and relevant features of their products. There are three Stirling engine developers producing 1kWe units aimed at the individual homes market. WhisperTech of New Zealand utilise a novel “wobble-yoke” kinematic engine with relatively low electrical conversion efficiency (12%), but with heat to power ratio and other physical characteristics making it suitable for typical family homes as a floor-mounted unit. Both BG Group and ENATEC have produced wall-mounted units with a combi-boiler function based on linear free piston technology with low vibration and higher efficiency generators (16%). However, it is believed that their relative sophistication may require a longer time to market than the WhisperTech unit which is planned for commercial availability in 2003. Sigma were developing a 3kWe engine, with high electrical efficiency (>25%) but development is currently stopped.

The two leading fuel cell developers are Vaillant, using the PlugPower stack as the basis of a modulating 5kWe unit suitable for multi-residential applications, and Sulzer Hexis, using a SOFC (Solid Oxide Fuel Cell) to produce 1kWe with the facility to add 35kWt to enhance thermal performance. Both companies are involved in field trials in collaboration with energy companies, but do not expect to have truly commercial units for at least 5 years. Fuel cell systems are expected to have electrical generation efficiencies of 30-60% with overall efficiencies of 70-90%. The only commercially available IC engine based unit is produced by Senertec in Germany with an electrical output of 5.5kWe and 10kWt thermal. However, at this scale it is a multi-residential unit with relatively high noise level making it suitable only for plant room applications. The need for catalytic emissions control, acoustic attenuation and extended service intervals impose severe cost and size constraints on the unit. It is understood that Honda are developing a 1kWe unit suitable for individual homes, but the limited reports in the public domain indicate that acceptable performance has yet to be demonstrated. Issues such as integration with the electricity distribution network and the home energy system are in the process of being addressed in Europe. In particular, network connection standards are being developed at European level (CEN Workshop Agreement) and in the UK (by the Electricity Association) to facilitate the simple, safe and cost effective connection of microCHP units. 7.3 Legal and institutional frameworks The external factors affecting the development of microCHP in Europe vary from country to country, but in general they fall into three categories: • Energy markets: in terms of the regulatory framework of energy markets, the important market actors, the degree of competition and the regulatory framework; • Electricity and fuel prices: including tax regimes, incentives and exemptions; and • Institutional factors: the policy context for CHP either enabling or restricting its deployment. Gas and electricity markets are in the process of transition to full competition across the EU and, to a certain extent, in the Eastern European countries awaiting entry to the EU. However there is great variation even within the EU: the UK has full competition for electricity and gas supply to the domestic sector, whereas in other countries the process is just beginning. Others, such as the Netherlands and Germany, have embraced competition in electricity and gas supply but this has yet to have an impact in the residential sector. In others, such as France, Italy and Greece, control of electricity and gas supply is still largely in the hands of state-owned monopolies. However even with open energy markets (and maybe because) access to small generators may not be easy or profitable. The high transaction costs of third party access to the electricity distribution network, which allows independent power producers to export selfgenerated electricity, is likely to prove a barrier to small scale CHP. Also, for example in the UK, electricity exported from a residential CHP unit, which is neither firm nor predictable but simply ‘spilled’ to the distribution network when the household cannot make use of it, typically achieves a very poor price per kWh. Energy prices vary widely across Europe, although the difference between electricity prices between countries is less dramatic than the difference in gas prices. Similarly the ratio between household electricity and gas prices varies widely between countries. For example, the ratio appears to be relatively high in the Netherlands and the UK; conversely, expensive imported gas in Italy creates a ratio less favourable to CHP. Over the long-term it appears that gas prices are set to increase at a faster rate than electricity prices, worsening the financial case for gas-fired CHP. However, microCHP may be able to benefit from the timevarying value of electricity exports (during the day, and during the year) and other embedded generation benefits such as avoided transmission costs, or the provision of ancillary services. In such a volatile area it is nearly impossible to draw firm conclusions for the future. In 2002, none of the countries examined had a coherent regulatory framework that specifically supported microCHP, or even CHP generally. For example, there is commonly a lack of grid connection procedures and simple market mechanisms to enable electricity generated from CHP to be sold, either to local electricity supply companies or to third parties. However, the underlying conditions for microCHP are improving, in particular through the continued liberalisation of European energy markets and the strengthening of climate change

policy, and while most national CHP policy is aimed at large and medium scale applications, special provisions for microCHP and other embedded generators are beginning to emerge. In Germany, for example, subsidies are offered for CHP installations of less than 2 MWe capacity and CHP below 100 kWe benefits from special metering rules. In the UK, policy work is underway to create standardised network connection procedures for domestic CHP. In the Eastern European Countries waiting to join the EU, conditions for the development of microCHP markets are currently poor, though this situation could improve radidly as the accession states link their policies and energy markets to those of the EU. 7.4 Market size modelling in the EU An econometric model was developed to estimate the potential size of the microCHP market in Europe under various scenarios for the period between 2001 and 2020. Three scenarios were modelled:- ‘business as usual’; the “medium effort” scenario - efforts made with regard to legislation, policy and financial incentives; and the “maximum effort” scenario strong action taken to promote microCHP technology. The results provide indicative figures for total number of unit sales in both the EU countries (and Norway) and the Eastern European countries. The results were used to calculate the environmental benefits in terms of CO2 emissions that could be saved by using microCHP technology. Three microCHP systems were used in the modelling, “a small (1kWe) Stirling engine”, “a large (3kWe) Stirling engine” and “a small (1kWe) efficient fuel cell”. For each system, an economic model was developed and interrogated to provide feedback on the parameters affecting the economic viability of that particular system. Calculations took into consideration the marginal cost of the systems over that of a new traditional boiler, the export value of electricity, the operation and maintenance implications of microCHP, the leasing arrangements of the system to the householder, overall cost to the customer and overall profit to the suppliers, amalgamated into a “service provider” or an Energy Service Company (ESCo). Information obtained from this model was then used to calculate the overall payback periods, and thus apportion market share to each of the three systems. Scenario modelling was based on variations in the buy-back price of the exported electricity, which was used as an indicator of the results of changes in legislation, policy and financial incentives, and as the most likely method to be used to subsidise the microCHP market. The model also calculated the penetration rate of each of the three systems in each scenario to illustrate the diffusion of microCHP into the market. A classic S-curve formula was used to estimate the rate of adoption of the microCHP technology based on implicit assumptions on a slow initial growth, subsequent rapid growth followed by declining growth as estimated saturation levels are achieved. Housing data collected in the project were used to estimate the maximum potential for microCHP in each country, based on the number of dwellings with central heating, heat demand characteristics and boiler replacement rates. Modelling was carried out for the 15 EU countries (and Norway) and separately for the Eastern European countries. The modelling showed that of the three systems, it is the small Stirling engine system that is likely to have the highest quantity of sales. This is due to the fact that this system has the lowest marginal costs, shortest payback period and can be utilised efficiently in the most dwellings, varying from apartments to large houses. For the EU as a whole, the modelling indicated that in the optimum scenario 12.5 million microCHP units could be sold, equating to annual CO2 emissions saving of 7.8 million tons of CO2, by 2020. Two countries stand out as having the greatest market potential in 2002 under scenario three, the United Kingdom and Germany. Other countries that have a high market potential are the Netherlands, Spain and Austria, while Norway and Sweden are unlikely to adopt microCHP due to the absence of significant gas distribution networks. For Eastern European countries, the modelling indicated that by 2020, around 670,000 microCHP units could be sold, with an equivalent saving of 1 million tons of CO2 per year. 7.5 Development of the Market The method by which microCHP could enter the domestic market is likely to be as a direct replacement for gas boilers in central heating systems. The study considered the alternative routes to this market and how these might influence the potential market. First, the direct sale route via the internet for example to enthusiasts, was considered, and thought likely to lead to installation and operational problems due to amateur involvement, giving the

product a bad name. Second, the conventional supply chain via established boiler distributors and installers, with the advantage of an immediate route but the fear that the additional cost of microCHP compared with a boiler could make it difficult to sell in a competitive market place. Third, the specifier route for large scale housing projects where microCHP could be installed in a whole area or building stock, which was seen as viable though limited in scale. And finally the “Service provider” or ESCo route, where the supply, financing and servicing of the microCHP unit, is provided to the householder, in conjunction with the electricity (and gas) supplier. This has the disadvantage of requiring new organisations and operating systems for which there are currently few precedents, but appeared to overcome most of the problems identified previously, such as higher capital cost, more complex installation and maintenance and product image. The project concluded that this was the most likely route, theoretically offering considerable benefits to all key players from manufacturer through to energy supplier and householder. The Service provider route, operated by a consortium of interested parties such as manufacturers, power companies, finance houses, installers and service organisations etc., could facilitate market entry of microCHP, maximising overall profit and minimising the negative impact of regulatory and other current market barriers. This is primarily because the range of additional revenue and profit streams accruing to the service provider, will be the motivating factor. Calculations show that the house holder of a large house can save 6-7% of their total fuel bill compared with an old boiler system, with zero expenditure, and this could provide an adequate profit for the ESCo, taking into account fuel supply, leasing, maintenance and the true time-related value of electricity generated.

8. CONCLUSIONS 8.1 Energy efficiency with gas in the home. There are many development in the use of gas for heating, cooling and domestic appliances in housing which have the potential to reduce primary energy consumption significantly. The integration of renewable energy sources, particularly solar water heating and ground sourcing of heat and coolth, linked with gas back-up is becoming an important and reliable addition. Solar water heating can supply more than 25% of annual domestic hot water requirements in northern European climates, with much greater levels in southern Europe. Gas driven heat pumps are now available, either ground or air sourced, and can provide both heating and cooling efficiently and effectively in Europe. Ground sourcing is still expensive and absorption heat pumps still require some development work for reliable applications. Domestic appliances are responsible for a large part of the total energy demand of modern housing in Europe and the use of gas as the principle fuel can provide large savings. The cooking and washing appliances demonstrated in the DEO project are readily available on the market and have been proven to perform well. The newest area of development is the generation of electricity in the home as part of a combined heat and power system, using gas as the fuel. This development has vast potential for replacing imported electricity from the grid by local generation using natural gas, as discussed below. 8.2 The European potential for microCHP The MICROMAP study has shown that between 5 million and 12.5 million microCHP systems could be installed and operating commercially in European Union Countries by the year 2020. This would result in CO2 emissions savings of between 3.3 and 7.8 million tonnes per year. The number installed will depend on many factors and these are discussed briefly below. In addition, there is the potential to install 700 000 units in Central and Eastern European countries, assuming that they accede to the EU to the anticipated timetable. The small Stirling engine microCHP systems producing around 1kWe are likely to take the largest market share, due to their widespread application, current advanced state of development and anticipated lower cost, compared with the alternatives. However, there are a number of barriers to the widespread adoption of microCHP as discussed below, including institutional, regulatory and financial barriers, the need for new private sector organisations and skills, the need to develop the technology to a reliable level

and to demonstrate this, and the need to convince the householder of the advantages of microCHP. Some progress is being made but much more is needed. Institutional, regulatory and financial issues will play a dominant role in the development of miniCHP in the different countries, though if current progress is maintained and deadlines for complete liberalisation of the European energy markets are met, there is no blockage to development of microCHP in most countries after 2010. However regulatory frameworks need to be developed and agreed in several areas, including for the microCHP systems themselves and for connection to the local distribution network. Due to the additional capital costs of installing microCHP compared with conventional boiler systems, financial incentives to stimulate the market are proposed by the study team. Commercial development of microCHP systems and ownership and management arrangements, are starting to take place and these are likely to be very different from the conventional boiler equivalents. Further technological developments are required in the component products to improve efficiency, reliability and generally to provide a suitable replacement to the conventional domestic boiler. Stirling engine systems are likely to be the first to be ready for the mass market, with fuel cell systems maybe coming into the market around 2010. Mass production facilities need to be developed and marketing, sales, installation and maintenance teams need to be trained to adapt to the new and relatively complex microCHP systems. Whilst microCHP systems could be sold via the conventional boiler manufacturing and installation chain, the study concluded that if microCHP is to be a significant replacement for the conventional domestic boiler a mass market is essential and other routes to market are necessary. The favoured route is via “service providers” or ESCo, comprising consortia of organisations including manufacturers, financiers, installers and energy supply companies. This route is seen as the way to minimise the installed cost of microCHP systems by reducing the costs associated with conventional supply chain “middlemen” and optimising the financial flows of the energy suppliers and the householder, whilst ensuring a reliable service for the householder. However it was recognised that few successful service providers of this type exist and that concerted private sector action will be required if this route is to be developed. A negative aspect of this route to market was seen as the possible backlash from existing boiler manufacturers and all those involved in the conventional supply chain, who could see a reducing market for their services over time. Initial markets for the new microCHP systems are thought to be the UK, the Netherlands and Germany due principally to the liberalisation of the energy markets in these countries but also to other factors such as high house heating demands, existing gas supply networks and social factors. In these countries there are opportunities for “specifier sales”, where owners or developers of housing areas or groups of housing, such as local authorities and private house builders of new estates, to negotiate directly with microCHP supplying consortia for mass installation and maintenance in one area. In Germany, it was also thought possible that there could be an early demand from individual house owners for microCHP systems. The householder will need to be convinced that changing his or her boiler for a microCHP system brings benefits which outweigh any disadvantages. The main benefits should be in reduced fuel costs, though if the system is installed through an ESCo, the whole package of finance, maintenance and gas and electricity costs will be what convinces the householder to change. It will thus be important that early installations work efficiently and reliably and are seen to do so. Marketing of systems and the benefits to householders is likely to form an important part of all early attempt to start the market for microCHP.