Is it worth it to add insulationYou’ll find lots of online calculators that estimate projected savings and the payback period based on information you provide about your home, current energy prices, and other variables. But these projections often vary dramatically from actual experience. Particularly avoid calculators or estimates provided by trade organizations.

One useful calculator comes from the Lawrence Berkeley National Laboratory (LBL). The Home Energy Saver audit tool provides a full assessment of your current energy use, possible cost-savings—including savings from adding insulation—and payback time for efficiency improvements. It also calculates energy and carbon emissions saved.

Actual energy savings from a given improvement vary according to the specifics of your home. If you use the LBL tool, or any other audit tool, the more information you put in, and the more specific it is, the more accurate the estimate of savings will be.

The table below shows the recommendations and cost-saving projections Home Energy Saver made for a hypothetical 1,800-square-foot two-story home in San Francisco.

Estimated Payback from Reducing
Leaks and Improving Insulation

Projected savings calculated by the Department of Energy’s Home Energy Saver website for an 1,800 sq. ft., 2-story home in San Francisco with a heat pump

Current Upgrade Projected one-year savings
Uninsulated, unfinished attic Insulate to R-38 $374
Unfinished attic with R-11 insulation Add R-27 of insulation to bring total to R-38 $106
Unfinished attic with R-11 insulation Add R-27 of insulation to bring total to R-38 and install weatherstripping $334

A caveat: These projections are rough guidelines based on average energy prices and other assumptions. But the projections clearly show that if you don’t have any attic insulation now, adding to the recommended level and sealing big leaks produces substantial savings that fairly quickly recoup the costs of the improvements.

You may be able to take advantage of rebates and incentives offered by your utility company to help pay for insulation improvements and air-sealing work. PG&E’s Energy Upgrade California Home Upgrade program offers rebates of $1,000 to $6,500 to homeowners who make energy-saving improvements—the more improvements, the bigger the rebate. The rebate amounts are calculated according to a point system, with more points awarded for tasks that have the greatest effects on efficiency. To get a rebate, you’ll have to complete several improvement projects—for example, if you pay for air sealing, attic insulation, and floor insulation, the rebate is $1,500; if you also install a new high-efficiency furnace, the rebate is $2,000.