Home energy audits in St. Louis

What does a home energy audit cost in St. Louis?

Ours costs nothing, before or after: the assessment is free and the report is yours either way. If you want the work done, it is priced in one line-itemed proposal, and what moves that price is the work, not the visit: attic area, how far the R-value has to climb, how many leaks there are, access, and anything that must be fixed first.

The utilities' own assessments are free to those who qualify. Ameren Missouri offers one to every residential electric customer through Pay As You Save, and CommunitySavers adds no-cost assessments and upgrades for income-eligible households through December 31, 2026, as funds allow. Ameren Illinois offers a free assessment to income-qualified households; for other customers its discounts start with a Program Ally's assessment, and its insulation page lists no price for that visit. Missouri households within federal income guidelines can apply for weatherization, which Spire says includes professional energy audits; Illinois runs its own program through county agencies. And 25C, the federal credit, does not reach anything placed in service in 2026.

What happens during the free assessment?

About an hour, most of it in the attic and under the floor. We measure the depth and type of the insulation and work out its R-value, photograph its condition, and run an infrared scan of the ceiling to show where heat is getting through. We look at the top plates, chases, hatch and other openings into the attic, and at the rim joist in the basement or crawl space where there is one. Two findings stop work on the spot: vermiculite, which EPA says to leave undisturbed and which we refer out, and live knob-and-tube wiring.

DOE's consumer guide suggests having two things ready: a list of problems you have noticed, such as condensation or drafty, uncomfortable rooms, and copies or summaries of recent energy bills. A clear path to the attic hatch and the basement or crawl space door helps too.

What is in the written report?

Numbers and photographs, not a pitch. The report gives:

• The R-value you have now, measured, beside ENERGY STAR's figure for this climate zone: R-60 for an uninsulated attic, R-49 where 3 to 4 inches are down.
• Photographs of the insulation, the openings into the attic and anything that needs attention.
• Where air is getting through, and what to seal before any insulation goes in.
• Anything that has to be handled first: vermiculite, live knob-and-tube wiring, a roof leak, or a vent blowing into the attic.
• The utility program rules that apply at your address, with their conditions.
• On request, a line-itemed proposal, with the permit noted where the city requires one.

The report is yours whether you hire us or not. Take it to another contractor or to a utility program if you like; it is written to be compared.

Free assessment or full blower-door audit: what is the difference?

Scope and equipment. DOE describes a professional audit as a detailed, equipment-based look at the whole house, usually built on a blower door test and an infrared scan run together, and it may include a check of the heating and cooling system, a test for gas leaks and a look at ventilation. ENERGY STAR's outline of a full assessment adds a homeowner interview, a review of past energy bills, an inspection of the envelope and every mechanical system, diagnostic tests for leaks, moisture and ventilation, and a prioritized list of improvements. A duct blower can measure leakage in the ductwork too.

Our free assessment covers the attic, the openings into it, and the crawl space or basement, with the R-value measured and an infrared scan, but no whole-house leakage number. The blower door comes in where the job calls for one, before and after the work. A full audit earns its place when a program pays on measured leakage, when gas or oil appliances and heavy sealing call for a combustion safety check, or when a comfort problem has no visible cause.

What do Ameren Missouri and Ameren Illinois offer in 2026?

Both offer assessments, on different terms. This is what each publishes:

• Ameren Missouri, Pay As You Save: a free, no-obligation home energy assessment for every Ameren Missouri residential electric customer, with free energy-saving products. If the house qualifies, you get an energy plan, a program partner you select installs the upgrades, and the cost is repaid through a fixed monthly charge capped at 80 percent of the estimated monthly savings, which includes 3 percent interest and a small close-out fee. The charge stays with the meter if you move; renters need the owner's written consent.
• Ameren Missouri CommunitySavers: a no-cost assessment and upgrades, attic insulation among them, for households in subsidized housing, at or below 80 percent of area median income or 200 percent of the federal poverty level, or in an area Ameren designates as high need. Ameren says the assessment and first product installs usually take about two hours.
• Ameren Illinois: a free assessment by an Energy Advisor for income-qualified households in single-family homes heated with gas or electricity delivered by Ameren Illinois, or by propane for Ameren electric customers. Other customers start with a Program Ally's assessment; Ameren suggests contacting more than one, and a qualifying home may get a project application estimating the discount and the out-of-pocket cost.

None of these is the assessment we offer, and ours does not stand in for one where a program requires its own.

Can you do a home energy audit yourself?

A rough one, yes, and DOE's consumer guide lays out how. Walk the house and look where different materials meet, such as brick and siding, foundation and walls, or chimney and siding, and around outlets, switch plates, window and door frames, baseboards, attic hatches, window air conditioners, and the points where wiring, gas lines and cable come in. On a cool, windy day, close the windows, doors and fireplace flue, turn off gas furnaces and water heaters, run the bath and kitchen exhaust fans, and pass a lit incense stick along likely leaks; wherever the smoke is drawn in or blown away, air is moving. A door or window that lets a sheet of paper slide out when closed on it leaks too.

Two more free checks: ENERGY STAR's Home Energy Yardstick scores a home's annual energy use from 1 to 100 against similar homes, with 50 as average, and its attic rule of thumb says insulation level with or below the tops of the joists probably needs adding to.

Why are the bills so high in an older St. Louis house?

Start with what sits above the top-floor ceiling and below the first floor. EPA's sealing guide places the most significant leaks in most homes in the attic and basement, ENERGY STAR says most U.S. homes lack enough insulation, and EPA's ENERGY STAR modeling for climate zone 4 puts the saving from sealing and insulating a typical home at about 12 percent of the total energy bill. In the Census Bureau's 2020–2024 survey the median St. Louis city home was built in 1939 or earlier and the median St. Louis County home in 1969, and 59 percent of the eight-county metro's homes predate 1980.

An audit in an older house also looks for what age brings: knob-and-tube wiring, which ENERGY STAR dates to before 1930, and vermiculite, most of it sold from a single asbestos-contaminated mine in Libby, Montana between 1919 and 1990, according to EPA.

Does an energy audit involve a permit or inspection?

The assessment itself is a look, not construction; it is the work afterward that may need a permit. Of the 45 jurisdictions we cover, only three publish a rule that reaches an attic top-up, and all three say no permit: unincorporated St. Louis County and Wildwood under the county's no-permit list, and Washington under its remodel exemption. That county list does require a permit to insulate, fur and drywall the room side of an exterior wall or the inside of a basement wall. In Illinois, state law applies the energy code to the part of a house being altered, and Edwardsville prints insulation minimums for remodels. We pull permits as part of the job where they are required.

Some Missouri codes reach existing homes too. St. Charles keeps the existing-buildings chapter of the 2015 IECC in force, and Arnold adopts the 2021 IECC without amendment, chapter included. Each town page states its own edition.

What should a St. Louis energy audit account for?

Three local facts change what an audit recommends. First, the heating fuel. In Franklin County 68 percent of occupied homes heat with electricity, in Jefferson County 58 percent, in the city of St. Louis 31 percent and in St. Louis County 23 percent, by the Census Bureau's 2020–2024 estimates, and Ameren Missouri counts only electric savings toward a PAYS copay. Second, the utility. Kirkwood runs its own electric utility, whose efficiency page mentions energy audits but publishes no insulation rebate, and parts of St. Charles County are on Cuivre River Electric Cooperative rather than Ameren. Third, the state line: the Missouri program is repaid on the electric bill, while Illinois takes its discount off a Program Ally's price.

The climate sets the stakes in both seasons: Lambert's NOAA normals for 1991–2020 count 1,713 cooling degree days on top of 4,433 for heating. Income-qualified households can also apply to their county's weatherization agency, such as the Urban League of Metropolitan St. Louis in the city or the Community Action Agency of St. Louis County, and on the Illinois side the agencies serving Madison, St. Clair and Monroe counties.

Common questions about home energy audits in St. Louis

Where we work

Home energy audits across greater St. Louis, from the city and St. Louis County out to St. Charles, Jefferson and Franklin Counties and across the river into the Metro East. Each city has its own page with the permit rule and code edition that apply there: