» Central heat strips turn on, off, on, off ...
even when the hallway thermostat is set to OFF. With everything in the house off or unplugged and the water heater switched off at the breaker panel, the meter races, stops, races, stops. Because of a thermostat, control wiring or other wiring problem, the central electric heating strips (10,000 to 20,000 watts) are coming on even though the distribution fan is off and all is silent. Without the fan running, heat from the strips is not distributed. Heat builds up around the strips until a high-temperature safety switch is activated, turning them off. They cool. They come on again.........and so on. Another rare problem like above, but costly when it happens.

» The resident is equipped with a so-called "combination appliance" that uses a gas water heater to heat the water as well as the house (or apartment)...
and in summer it keeps on sending heat to the house! Rare, but it happens as a result of failed electronic controls or system valves. Electric and gas costs both increase. The electric cooling cost typically doubles. For the energy auditor, higher than expected summer gas cost is often the telling clue.

» The fireplace damper is open, or there's no damper at all...
admitting outdoor air or losing indoor air. Costs rise in either case, especially if there are HVAC duct leaks, and there usually are. One of our energy auditors took an informal survey of his customers last spring, asking those with fireplaces whether their dampers are closed. Among those who thought it was closed, about 50% were wrong: It's open.

» With a fireplace going, keep doors to other rooms closed - or keep the furnace off until you need it.

» If the thermostat faces a frequently used fireplace, or is close by, move it to the far end of an inside wall or to another room with no alternate heat source.