Space heating is the largest energy expense in most homes, accounting for two-thirds of annual energy bills in cold climates.
Heating is the largest energy expense in most homes, accounting for almost two-thirds of annual energy bills in colder areas of the country. Heating systems in the United States emit a billion tons of carbon dioxide (CO2) and about 12% of the sulfur dioxide and nitrogen oxides emitted by the nation. Reducing energy use for heating is the single most effective way to reduce your home's contribution to global environmental problems.
Conservation efforts and a new high-efficiency heating system can often cut your pollution output and fuel bills in half. Upgrading your furnace or boiler from an AFUE (annual fuel utilization efficiency) of 56% to 90% in an average cold-climate house will save 1.5 tons of CO2 emissions if you heat with gas or 2.5 tons if you heat with oil and will cut your heating bill by almost 40%.
If your furnace or boiler is old, worn out, inefficient, or significantly oversized, the simplest solution is to replace it with a modern high-efficiency model. Old coal burners that were switched over to oil or gas are prime candidates for replacement, as well as gas furnaces without electronic (pilotless) ignition.
A central furnace or boiler's efficiency is measured by annual fuel utilization efficiency (AFUE). AFUE is a measure of how efficient the appliance is in using fossil fuel (gas or oil) or electricity (for an electric furnace) over a typical year of use.
An all-electric furnace or boiler has no flue loss through a chimney. The AFUE rating for an all-electric furnace or boiler is between 95% and 100%. The lower values are for units installed outdoors because they have greater jacket heat loss.
The efficiency of manufactured furnaces is governed by the National Appliance Energy Conservation Act of 1987 and regulated by the U.S. Department of Energy. The minimum allowed AFUE rating for a noncondensing, fossil-fueled, warm-air furnace is 78%; the rating for a fossil-fueled boiler is 80%; and the rating for a gas-fueled steam boiler is 75%. A condensing furnace or boiler condenses the water vapor produced in the combustion process and captures the heat released from this condensation. The AFUE rating for a condensing unit can be much higher (by more than 10 percentage points) than a noncondensing furnace. Although a condensing unit costs more than a noncondensing unit, the condensing unit can save you money in fuel costs over the 15 to 20-year life of the unit.