Smarter Living: Energy

In Step 2 of our series, we covered sealing and insulating the home to keep in the warm air. In Step 3, we look at how you heat the air in the first place. As daunting as it may seem to maintain your furnace, every homeowner should know how to change furnace filters and should also install a programmable thermostat. Below we outline how to do just that with our simple step-by-step guide.

With your home energy audit (see Step 1), you should have received detailed information about your furnaces performance and recommendations regarding upgrade. If you have not conducted an energy audit, here’s what you need to do.


1. Every furnace has an annual fuel utilization efficiency (AFUE) rating, which indicates how efficiently it burns heal oil, natural gas or propane. Essentially the rating is a breakdown of how much energy is converted into heat and how much escapes in the form of heat-trapping gases. An AFUE rating of 90 means 90 percent efficiency, with 10 percent being released into the environment.

2. If your furnace has an efficiency rating of at least 70 percent, it pays to invest in energy saving strategies. You can make the heating system more efficient, saving you money and releasing fewer greenhouse gasses into the atmosphere. Older furnaces with efficiency ratings under 70 percent can be retrofitted with new components or replaced entirely with models up to 97 percent efficient, and you'll save money in the long run. But the AFUE rating indicates the best case scenario, assuming the rest of the system is in optimum working order. To ensure this is the case requires regular maintenance. Additional savings can be made by changing and/or regimenting home heating habits and routines.

3. First, determine the kind of system heating your home: Boiler systems heat by circulating hot water through pipes or by steam circulated through radiators. Furnace systems heat by circulating hot air through ducts and vents. The air may be passive, rising through the ducting because it is warmer than the ambient temperature, or forced, dispersed by an electric fan. The most common fuel source for these different systems is usually oil (i.e. diesel), natural gas, propane, or electricity. Most electricity is generated by burning coal, so it is generally the least desirable. In much of the country, natural gas has the advantage of being cheaper than both diesel and propane.

4. Have your heating system checked by an expert (again, this is if you haven’t already conducted a home energy audit). Often contact information for the company that installed the furnace or boiler is posted on the appliance. They can give you a run down of ways to make the system run more efficiently.

Maintenance tasks to be conducted by a professional

Hot air systems:

  • Test for carbon monoxide.
  • Clean and lubricate the blower.
  • Check and repair duct connections.

Hot-water systems:

  • Test pressure relief valve.
  • Test high-limit control.
  • Verify pressure tank is filled with air not water.

Steam systems:

  • Periodically, have boiler drained to remove sediment.
  • Test low-water cutoff safety and high-limit safety controls.
  • Drain float chamber to remove sediment.
  • Augment boiler water to control deposits and corrosion.

Common maintenance tasks you can do yourself

  • With furnace systems switch to a 10-year permanent filter and clean it regularly (see p. 2 for how-to)
  • Swap out your old thermostat for a programmable one (see p. 2 for how-to)
  • With oil-run boilers and furnaces have the fuel filter replaced on a regular schedule.
  • With low- and mid-efficiency systems the heat exchanger requires periodic cleaning.
  • Inspect vent, vent pipe, and/or chimney. Look for cracks, bad joins, and old caulk.
  • Inspect heat exchanger for cracks and leaks. In boiler systems visible water may mean the heat exchanger need to be repaired.
  • Adjust oxygen/fuel mixture as necessary.
  • Remember, anything involving fuel lines should be handled by a certified technician.

While a professional should conduct these tests, here are two important upgrades you can do yourself:

Cleaning or replacing the filter

All forced air furnace systems have filters to preserve air quality. A dirty filter means greater air resistance, which, in turn, means more work for the blower. A clean filter can cut heating costs by as much as 5 percent. Beyond the savings, clean filters keep dust and mold spores out of your house, helping reduce allergy symptoms. They can also prevent more expensive maintenance work or even equipment failure. During periods of heavy use a disposable filter should be changed once a month. Maybe it's time for a cleanable, 10-year permanent filter.

Reusable furnace filter

1. Turn off power to the furnace, either at the circuit breaker or the furnace on/off switch.
2. Vacuum area around furnace.
3. Remove the filter. The filter's location varies between furnace models, but is often behind the front service panel. It is also common for the furnace to have how-to diagrams for basic procedures. No tools should be necessary, and the panel will either lift or slide out. In some cases you may need a screwdriver to remove it.
Noting how the filter is positioned, in particular the directional arrows on the filter frame, remove and inspect it for dust build-up.
4. Replace with reusable filter or clean existing reusable filter.
5. Before installing the new filter, inspect the interior of the furnace from the access area. Vacuum dust and cobwebs.
6. Install the new or newly cleaned filter, replace the access panel and turn the power back on.

Install a programmable thermostat

To save on heating and cooling bills, your quickest fix is to install Energy Star-rated programmable thermostat. With control of the temperatures at anytime of the day, you can remain comfortable while lowering heating and cooling costs by 20 to 30 percent.

3/16” drill bit
Masking tape
Small level

1. Turn off power to the thermostat, either the furnace for the breaker box. Familiarize yourself with the new product instructions.

2. Remove the cover of your old thermostat.

3. Unscrew the thermostat from the wall plate.

4. Before disconnecting the wires, label each with the letter of the screw to which it is attached.

5. Unscrew the wall plate.

6. Ensure that the wires do not slip back into the wall. If your old thermostat contains mercury (look on the back for a glass tube with the mercury inside), disposed of as hazardous household waste.

7. Using the level, place the new thermostat's wall plate over the existing hole, making sure that no wires are trapped behind it. Mark drill spots on the wall through the plate's screw holes.

9. Drill holes, then screw on the wall plate.

10. Attach the letter wires to their corresponding screws, following instructions from new thermostat.

11. Attach the new thermostat to the wall plate. Turn the power on at the circuit breaker or furnace, and program the thermostat according to the instructions.


For Federal tax incentives, the DOE provides up-to-date tax credit information, and the Tax Incentives Assistance Project offers information about the limits on energy efficient home improvements. Be sure to check out the DOE’s “5 Things You Should Know Before You Claim Your Energy Tax Credit." For a listing of state incentives, visit the Alliance to Save Energy. Energy Star provides a searchable database of current rebates and special offers on Energy Star qualified products. Searches are cross referenced by product and zip code and include boilers, furnaces, and thermostats.


For renters responsible for the cost of fuel, it may be difficult to motivate your landlord to take an interest in improving the existing heating system. Educating them about tax credits and incentives may be worth your while. And who knows, pointing out the environmental benefits might find a sympathetic ear. For houses and apartments with thermostats, switching to a programmable model will make a difference. Remember, any strategy that results in decreased fuel consumption, means a lower heating bill and fewer heat-trapping emissions. In this regard, new habits can be as significant as new technology. Getting used to a lower room temperature, turning the heat down or off when your away, and regular home energy audits are all measures that will impact the month-to-month bottom line.

last revised 4/15/2011

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