If there’s a rule of thumb you can apply to maximizing comfort while minimizing your heating or cooling bills, it’s that being eco-friendly is a long-term investment that will pay off for both you and the value of your home.

Furnaces:  Operating costs should figure prominently in your decision to buy a furnace. In descending order, propane, electric and oil furnaces cost the most to operate, with natural gas being the most economical.

The energy efficiency of a furnace is measured using an AFUE (Annual Fuel Utilization Efficiency) rating. Older, conventional furnaces have an AFUE of 60 percent, which means that 40 percent of the heat provided escapes up the chimney. High efficiency furnaces operate at 90 percent efficiency or more.  Prices vary based on the unit, so it pays to shop around.

But how about a furnace that keeps you warm and produces electricity?  New “micro-combined-heat-and-power” units, or CHP, turn natural gas into hot water and generates up to $800 a year in electricity. At least five companies are building micro-CHP systems worldwide. In the United States, Marathon Engine Systems of East Troy, Wisconsin, offers a 4-kilowatt hot-water system.   With these furnaces, more than 90% of the energy that is produced as heat and electricity is utilized, with CO2 emissions at 65% below a coal fired power plant (source: www.marathonengines.com). The Micro-CHP units run from $13,000 to $20,000, including installation.

Heat pumps:  In essence, a heat pump is a device that moves heat. In the winter, a heat pump draws heat from the outdoor air (all air has some heat) or the ground (all ground has some heat) and circulates it through ducts into your home. During the summer, it reverses the process and draws heat from your interior air and releases it outdoors, either into the air or into the ground.  Heat pumps do not burn fuel directly, and cost less to run than an electric furnace.

They also come with additional features. For example, two-speed eco-friendly units can run on low-speed most of the time while using about 50 percent of the energy. Therefore, they offer fewer on/off cycles and produce fewer drafts, less obvious temperature swings and improved air circulation. Heat pumps can range from about $800 into many thousands of dollars depending on the size of your home and the features you want.

Air Conditioners:  Air conditioners come in many forms and sizes today, from the central house unit delivering cool air through your vents, to portable, room-specific ones that fit in windows. The alternative is to cool rooms independently, using closed circuit “roll-from-room-to-room” units that cost in the $500 to $800 range. Full housing units can range from about $1500 upward depending on the size of your house and the deal you can cut if installed during the “low business” season. Recently, ice air coolers and mini-eco-ice coolers have also debuted at a cost below $200.