The most important thing most people can do to cut their electric and natural gas bills is reduce the amount of energy they use for heating, ventilation and air conditioning (HVAC). This is because most – up to two-thirds – of money spent on energy in a home is for climate control. The rest is split between lighting, water heating, cooking, refrigeration, electronics like TV and computers and a variety of specialized devices.

The HVAC system itself is probably the most important part of the HVAC portion of a residential energy bill. Replacing an old HVAC system with a modern heat pump will include air conditioning. If you haven’t had air conditioning before, it is still likely to produce energy savings: The heat pump may save more energy during the heating season than it will consume during the Pacific Northwest’s short cooling season. Ducted furnaces can be replaced with ducted heat pumps. Strip heaters and wall unit air conditioners can be replaced with ductless heat pumps.

Insulation is probably the second most important factor in the HVAC portion of the energy bill and the most important if the building is poorly insulated. Old building codes may have required little or no insulation. Adding insulation to a previously uninsulated building can cut total energy use by almost half. Even in newer buildings, which were insulated originally, an insulation retrofit may reduce total home energy bills by 20% or more.

Total HVAC energy use can be significantly reduced by lesser-known technologies, too. For instance, radiant barriers – essentially, reinforced aluminum foil – can be hung under roof rafters to reflect heat back into the home in winter and to reflect heat back out through the roof in summer. Radiant barriers require some space above and below them to allow heat reflection. If they are too close to the roof, they just transfer heat through the metal foil. If space is available, they are usually inexpensive to buy and install and can reduce HVAC energy use by as much as another 20%.

Modern two- or three-pane windows with reflective coatings should be used to replace older single-pane, damaged two-pane, or uncoated two-pane windows. Replace thermally conductive aluminum frames with vinyl or wood frames. Aluminum window frames don’t provide much resistance to building heat transfers. Full-house replacement of uncoated single-pane windows in aluminum frames, with coated three-pane vinyl-framed windows, can reduce HVAC energy use by still another 10–20%.

Our average winter electric bill, in a single-family home in Shelter Bay, was $750/month when we moved in. The house had a 25-year old electric furnace, damaged aluminum-frame two-pane windows and 40+ year old insulation. After installing new windows and a new heat pump and upgrading the insulation, our winter electric bill averages $300/month.

Even with that great result, we can do more. We haven’t installed radiant barriers yet. The new heat pump came with a programmable thermostat, which we haven’t programmed. Setting the thermostat at lower temperatures when Jenelle and I are out, while getting it back to comfortable temperatures before we get home, could reduce our HVAC energy use by another 10–20%.