A micro combined heat and power (chp) system is a very reliable and efficient replacement for domestic hot water. Micro CHP systems have been used widely in Japan and some parts of Western Europe. They add tremendous value for cold weather climate homes when heating a home and using the burn off heat (byproduct) generated to supply electrical power to the residence.

On a multi-family application we would look to use a micro chp system as a primary domestic hot water source. The reason is because that is where we can get the most use out of the system for our money. If the property was in a very cold climate where heating a unit was done for eight months of the year or more we could look to coupling it with our electric. A two unit micro system, master and slave with a buffer tank, can supply hot water for roughly 80 units. More units would require additional systems. For large properties a standard chp system can be considered, but drawbacks are space requirements, possible noise, and some exhaust. The benefits are that you would be producing more power to sell excess power back to your utility at favorable prices.

Looking at micro chp to supply hot water to 80 units the following numbers are typical. A master and slave set up produces a thermal output of 43,000 Btu’s/hr. Energy production would be 4.7 kWh/hr. or 6.6 megawatts per year. The production lifespan is 40,000 hours and maintenance needs to be done every 4,000 hours of use. One final point: a chp system is most effective when it is in constant use. The EPA has a new program dealing with chp systems. Go to http://www.epa.gov/chp/index.html to learn more about a 10% tax credit.