The ecopower™ microCHP works with propane to produce both heat and electricity-and long-term value for your homeowner.

As builders look for new ways to make their homes energy smart, an in-home power generator offers a unique tool for cutting carbon emissions-and utility bills. Marathon Engine Systems in East Troy, Mich., makes a small engine that works with propane or natural gas to heat a home while simultaneously producing electricity that can be consumed on site or sold to a local utility company. An example of a residential (or “micro”) combined heat and power (CHP) system, Marathon’s ecopower™ unit offers construction pros an innovative solution for off-grid performance building.

“If someone puts a pound of propane through a water heater, maybe 90 percent is used to heat the water and 10 percent goes up the chimney,” explains Marathon general manager Michael Schildt. “That same propane being put into an ecopower microCHP will generate the heat needed to make the hot water, and at the same time produce electricity as a byproduct of making the heat.”

The ecopower unit is compact and runs as quietly as a refrigerator, the company says. Here’s how it works: The propane internal combustion engine generates heat, which is routed through a heat exchanger to capture the energy leftover by the combustion process; that energy is stored in a 250-gallon buffer tank in the form of hot water. Running along with the heating cycle is an electricity generator whose power is tied into a standard junction box. The electricity is either used on site or sent to the utility.

These cogeneration units, as CHPs are also called, can pay for themselves fairly quickly, whether they’re used in cold climates, where there’s a long heating cycle, or in warm ones, where backup generators often are used to supply power to a home during grid outages. Schildt installed two ecopower units at his father’s new 5,000-square-foot Wisconsin home. The units make electricity all winter as well as supplying hot water to the home’s hydronic heating system.

“He receives checks quarterly from the utility, because the power [the units] produce while heating the house is so much greater than what he consumes,” Schildt says. “One winter he ended up getting $800 back.” That’s above and beyond the energy he created and consumed himself. Through such savings, Schildt expects his father to recoup his investment within five years, assuming the utility’s current payment rate of 10.7 cents per kilowatt hour.

Each ecopower unit generates about 4.5 kilowatts of electricity. Running at full power over a 24-hour period, it produces more than 1 million Btu of heat, and over 30 days of operating it can make 3 megawatts of electricity.

Marathon says its microCHPs also work with forced-air furnaces via a fan coil in the air handler, as well as geothermal systems. “Any system that requires thermal energy, we can work with,” says Marathon’s sales and marketing manager Michael Monohan.

For the truly green-conscious construction professional, a microCHP offers the added benefit of being a more eco-friendly source of electricity than energy purchased from the grid. Because the electricity is created on site, there isn’t the waste associated with transmission of energy over long distances, which helps reduce the greenhouse gas emissions that are a byproduct of power generation.