How to replace your furnace

Calculate your energy savings payback

Knowing how much a new furnace will reduce your gas bills can help you decide how much extra to spend (or not) on a more efficient model. The higher your fuel bill and the greater the increase in efficiency, the shorter the payback period.

According to the Washington, D.C.-based American Council for an Energy-Efficient Economy (ACEEE), if your old furnace has a pilot light, it’s probably 65% efficient. In this scenario, upgrading to an 80% efficient unit would reduce your gas bill by $19 per $100.

If your annual gas bill from heating is $1,000, you’ll save $190 per year. Assuming the new furnace costs $3,000 installed, you’ll recoup 6% annually ($190/$3,000). It would take 16 years to recoup your investment.

That's too long.

Use ACEEE’s chart to calculate your energy savings from upgrading.

Furnace usage also affects your electric bill. The furnace’s blower fan, which circulates hot air, runs on electricity. Electricity use varies significantly among furnaces.

A variable-speed blower can reduce electricity bills but can also increase the furnace’s price.