How a Home Energy Audit Can Save You Money

Updated: Mar. 20, 2024

A home energy audit can help you identify where you are losing energy and what you can do to stop it.

If high energy costs are causing you shock and frustration, take heart. There’s something you can do — call your local utility company and ask for an energy audit.

In this article, we’ll walk you through a professional energy audit and show you how it works. We teamed up with Erik Lindberg, a Minnesota state-certified energy auditor whose company, Enervision, has performed more than 12,000 audits.

What Is a Home Energy Audit?

During a home energy audit, an auditor will come to your home and conduct a series of tests to provide detailed information about your home’s energy usage and energy loss. It takes about two to three hours. The report will detail:

  • The condition and efficiency of your heating and cooling system;
  • The overall efficiency of your home, including the primary areas of air leakage in your walls and ceilings;
  • Low-cost ways you can improve energy efficiency and save energy;
  • Larger upgrades that will pay back their cost with energy savings within a relatively short period.

How Much Does a Home Energy Audit Cost?

Typically between $200 and $600. The actual cost may be higher or lower depending on the property size, complexity of the audit and the company doing it.

To find out the exact cost, contact your utility provider. Ask about tax credits or rebates. The Inflation Reduction Act (IRA) offers a tax credit of up to $150 for home energy audits. Scheduling an audit through your utility will likely be cheaper and easier than seeking one out on your own.

Can You Do Your Own Home Energy Audit?

Yes. While a professional energy audit is the best way to determine your home’s overall efficiency, an experienced DIYer who can locate drafts and replace light bulbs can identify and fix some straightforward problems.

Simple things you can do include improving attic insulation levels, closing gaps around electrical outlets on exterior walls, caulking windows and replacing light bulbs and fixtures with energy efficient alternatives. An energy audit will most likely include all these if your current home lacks them, greatly impacting your energy usage and the efficiency of your home.

What a Home Energy Audit Checks

Heating and hot water systems

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The audit starts with a furnace combustion efficiency test.

With the furnace running, Lindberg inserts a gas analyzer into its draft diverter. If there’s no draft diverter, he drills a small hole in the flue for the wand, then patches it later. The analyzer provides an immediate reading.

Our furnace had a 76.9 percent combustion efficiency — not bad considering furnaces at least 15 years old are usually 55 to 68 percent efficient, and this unit is 27 years old. (Typical lifespan is 15 to 20 years.)

This test also measures:

  • The amount of carbon monoxide in the flue gases;
  • Draft pressure in the flue to determine if gases could leak into the house.

These are safety issues. If waste gases aren’t going up the chimney, moisture, carbon monoxide and other pollutants could be flowing into your home (i.e. back-drafting). Common causes of vent problems are birds’ nests in the vent pipes, or vents that have come apart.

“If you have moisture on your windows,” Lindberg says, “the first thing to check for is back-drafting in the furnace and water heater flues.”

Lindberg tests for back-drafting in the water heater vent flue as well, by holding a flame or a smoke stick next to the draft diverter.

The check of the heating and hot water systems concludes with a visual inspection. Rust particles (called “scaling”) inside the furnace heat exchanger indicate corrosion, eventually leading to holes and combustion gas leakage. Scaling may also be visible on top of the water heater around the draft diverter.

Lindberg looks to see if the furnace filter is clean and installed correctly. “Clogged filters can cause a moderate increase in heating costs,” he says. “But more significantly, [it can] cause the heat exchanger to overheat and fail, and cause the fan motor to heat up, increase electric consumption and reduce the life of the motor.”

He also looks for combustibles stored near the furnace or water heater, because the flame could cause an explosion.

Other common problems Lindberg finds include disconnected flue pipes, leaky ductwork, clogged condensation pipes, dirty burners, and dirty fan blades.

“I’ve found many furnaces missing the cover for the filter slot, and major leaks in the return-air ductwork,” he says. “This causes depressurization in the furnace room and can draw dangerous exhaust gases out of the flue pipe and distribute these gases throughout the house.”

Air leakage

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Part Two of the audit entails a “blower door” test, which measures the home’s “tightness,” or air infiltration rate.

Lindberg first closes all doors and windows, then sets an adjustable panel with a variable-speed fan in a doorway, completely sealing it. He turns on the fan to blow air out of the house, which reduces the indoor air pressure, then measures airflow through the fan at predetermined pressure points. Outside air then enters through cracks and gaps in walls and ceilings.

With the fan running, you can feel air come in with your hand, especially around leaky windows and doors. Gauges connected to the fan measure the airflow rate needed to maintain a constant pressure. This allows the auditor to calculate the leakage rate.

Newer homes are built tighter under the most recent Minnesota building code. (Most other state codes have tighter rules too.) It even requires special ventilation fans to ensure adequate fresh air. Still, their leakage rate is often equivalent to a 6- by 6-in. hole in a wall.

Older homes weren’t built nearly as tightly. They often have a leakage rate equivalent to a 19- by 19-in. hole, which is like having a window wide open all the time! The house we tested had leaks totaling .77 square feet (about an 11- by 11-in. hole). Lindberg estimates that sealing air leaks alone will save 10 to 20 percent on this home’s annual heating bills.

Lindberg pointed out several signs of air leaks: stains around bath fans and dirt on insulation. A batt of insulation between joists in the basement was dirty, meaning the insulation served as a filter for air leaking in through the foundation.

“You can’t fix these leaks with insulation because it won’t stop the airflow,” he says. “You have to seal them with caulk, expanding foam, or some other sealant.”

In Lindberg’s opinion, there’s no limit to how tight you can make the ceiling.

“The less air that goes out the ceiling, the less that will come in around doors, windows, and other leaky areas,” he says. “When you’re carrying water in a bucket, it doesn’t matter if the top leaks because no water is going to get out. What matters is the bottom. Think of your house like an upside down bucket holding heat.”

Sources of energy loss

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While the blower door test measures the overall leakiness of the house, infrared scanning (technically called “thermography”) graphically identifies the precise locations of those leaks. Lindberg keeps the blower door fan running to draw in outside air. Then, using an infrared camera, he scans the walls and ceilings, photographing surface areas that show up as cooler.

Cold areas show up as blue, and warm areas as yellow. On a chilly day in March, the framing members showed up as blue, since they were cooler than the insulated portion of the walls. The opposite would be true on a hot day with an air-conditioner running indoors.

Air leaks in the ceiling typically cause the greatest energy losses. Openings made for light fixtures, plumbing vents, exhaust fans, attic access and smoke alarms will leak if the builder doesn’t efficiently seal them.

In this house, the area around the attic access panel and the exhaust fan in the upstairs bathroom showed extensive leaking. A ceiling light fixture, which must have been sealed better, leaked very little.

Electrical outlets and light switches on outside walls also usually leak, unless the builder took extra pains to seal them. The infrared scan showed four in the north kitchen wall leaked profusely. The homeowner confirmed this, noting that she often felt cold drafts when standing by this wall.

While some of these problems are easy to fix — insulating attic doors, spray foam or caulk around the exhaust fans, and foam seals under the outlet and switch cover plates — others are difficult to seal and may not be practical to fix. Leaks around exterior wall top plates and inadequate insulation in some wall cavities are common but hard to access, therefore expensive to remedy.

Expect some air leakage around windows, sliding patio doors and exterior doors. “All doors will leak,” Lindberg says. “Especially since people step on the threshold as they enter and leave the house, wearing a gap between the door and sill. The only doors that don’t leak are the ones on submarines.”

Final Report — What You Can Save

Once the testing is complete, the auditor prepares a comprehensive report detailing the amount of leakage, ways to improve efficiency, the cost of specific improvements, and the time frame for recouping those investments. The report lists specific low-cost steps for reducing energy consumption you can usually do yourself.

For this house, they included insulating the attic access panel, weatherstripping it with closed-cell foam tape, sealing ceiling penetrations at electrical fixtures, insulating kitchen soffits, adding attic insulation, insulating the rim joists, and caulking around windows, doors and base trim.

Lindberg estimated these upgrades will cut annual energy bills by 15 to 20 percent. Adding insulation to exterior walls isn’t worth the cost.

The furnace, installed when the house was built, had an annual fuel utilization efficiency (AFUE) of about 68 percent. That’s well below the current minimum standard specified by the building code and far below the efficiencies currently available. (Energy Star furnaces must be at least 90 percent AFUE.)

Lindberg recommends upgrading any furnace in Minnesota’s cold climate that’s not at least 80 percent efficient, since newer models use less energy and eventually pay for themselves (in nine years in this case). Your energy auditor will make these calculations and recommendations based on your local climate. Furnaces that are at least 95 percent efficient may qualify for a federal tax credit.

Installing a programmable thermostat in this home will pay for itself in just two to three years. A new high-efficiency air conditioner isn’t a priority, but it’s likely to be in warmer climates. You want to recoup your investment through predicted energy savings within seven to 10 years.