(adapted from The Consumer’s Guide to Effective Environmental Choices by Michael Brower and Warren Leon, 1999)

First of all, if you have an old heating or hot water system, consider installing a new, efficient one. If the home you live in has a very old furnace of steam boiler (one installed more than 25 years ago), it is probably not very efficient and not only produces more pollution and carbon dioxide than it should but also adds unnecessarily to your heating bills. A new furnace or boiler could cost $2,500 or more (installed), but if it substantially improved the efficiency of your heating system, you might save $200 ore more annually on your heating bills, and you will certainly reduce your household’s environmental impact.

There are also less expensive tricks you can use to improve the efficiency of an older heating system without replacing the furnace or boiler, such as installing flue dampers to keep heat from escaping out of the house when the furnace or boiler switches off.

If you have the option to change the type of fuel your heating system uses, you should probably choose either natural gas or an electric heat pump. Gas burns more cleanly and efficiently than oil, and gas furnaces (which heat air, as opposed to boilers, which heat water) can be as much as 95% efficient, meaning that 95% of the energy from the gas gets transferred to the air and sent through the house.

Electric heat pumps work like refrigerators, pumping heat from the outside into the house or (during warm weather) from inside out, like air conditioners. Exceptionally good heat pumps can deliver more energy than they consume, even considering the large amount of energy lost in electricity generation. Heat pumps that transfer heat from the outside air are not efficient in very cold weather, though. Where winter temperatures frequently drop below freezing, you may want to consider a ground-source heat pump (which transfers heat to and from the ground, where the temperatures are steadier). They cost more but are even more efficient than standard heat pumps.

When it comes to hot water heating systems, some types–especially natural gas ones–are more efficient than some of the other types. In addition, you can also consider solar water heating. If your present water heater uses electricity, then adding a solar collector and an extralarge storage tank (to handle cloudy days) can reduce your electricity consumption for water heating (by 40 to 90%) and make economic sense. A typical solar water heating system costs $3,000, a hefty sum, but it can save $150 to $350 per year, depending upon the local climate. (In the Northeast, the savings are likely to be at the lower end of this range.) Solar systems can make especially good sense for including on a new house, since, if the price of the new system is added to the purchase price of the house, the monthly savings on the electricity bills will often be greater than the increase to mortgage payments.

Every situation will be different, however. To find out what options you may have for improving or replacing your current heating and hot water systems, you will have to consult an expert. Many electric utilities and gas companies offer free home energy audits, or you can pay a modest amount for one yourself.