What Is a Home Energy Audit?

A home energy audit is a systematic evaluation of how your home uses energy — and where it loses it. Unlike a simple utility bill review, a thorough audit uses diagnostic tools to find the actual sources of inefficiency in your home's envelope, equipment, and systems.

The connection to solar is direct: your current utility bill reflects your current efficiency level. If that efficiency level is lower than it could be, a solar system sized around your current bill will be larger and more expensive than necessary. The audit tells you how much smaller your bill could be — and therefore how much smaller your solar system can be.

What a Thorough Energy Audit Includes

Blower Door Test

A blower door is a calibrated fan mounted in an exterior doorway. It depressurizes the home — temporarily pulling air out — which makes gaps, cracks, and leaks in the building envelope visible as incoming air. The test measures your home's air changes per hour (ACH), which quantifies how leaky your home is.

Air leakage is often the single largest source of heating and cooling loss in older Illinois homes. A poorly sealed home can lose a significant amount of conditioned air through gaps around windows, doors, penetrations, and the attic floor — all of it replaced by outdoor air your HVAC system has to re-condition.

Thermal Imaging

Infrared cameras detect temperature differences in walls, ceilings, and floors. On a cold day, areas with missing or inadequate insulation show up as cold spots on the camera. This makes insulation gaps, thermal bridges, and air leaks visible in a way that's impossible to see with the naked eye.

HVAC Assessment

The auditor will evaluate your heating and cooling equipment — age, capacity, efficiency rating, and current operating condition. Systems running significantly below their rated efficiency, or systems that are over- or under-sized for your home, can contribute meaningfully to high bills.

Utility Bill Analysis

A 12-month bill review identifies usage patterns and baselines. Unusually high consumption in heating or cooling months, compared to the home's size and age, can point to specific equipment or envelope issues.

Written Report With Prioritized Recommendations

A quality audit concludes with a written report that prioritizes findings by impact. The best auditors give you estimated energy savings and rough costs for each recommended improvement — so you can evaluate each one on its own merits before deciding what to do.

How Audit Findings Flow Into Solar Sizing

Here's the connection most solar companies skip: once you know which efficiency improvements you're going to make, you can estimate your post-upgrade energy consumption before designing the solar system.

If your audit finds that new windows and improved attic insulation will reduce your heating season consumption by a meaningful amount, the solar proposal should be built around that lower number — not your current, pre-upgrade usage.

This changes the solar system size. Fewer panels are needed. The system costs less. The payback period is shorter. And the system is sized for your home as it will actually perform over the next 25 years — not for the home you're leaving behind.

What to Look for in a Home Energy Auditor

  • Certification — Look for auditors certified by BPI (Building Performance Institute) or RESNET. These certifications indicate a standardized approach and training in diagnostic testing.
  • Diagnostic tools — A real audit uses a blower door and infrared camera, not just a visual walkthrough. If the auditor doesn't use these tools, the findings will be incomplete.
  • Written report — The deliverable should be a written document with specific findings and prioritized recommendations, not a verbal summary at the kitchen table.
  • No conflict of interest — Ideally, the auditor isn't also selling you the improvements. If they are, make sure the recommendations are prioritized by impact, not by what they sell.

The Audit and Your Solar Proposal

When SPM evaluates a home for solar, the process starts with the home's energy picture — not just the roof. We review your utility bills and evaluate the building for the most common efficiency gaps. If significant improvements are identified, we help you understand the cost and impact of each one before sizing any solar system.

The goal is a solar proposal built around your home's actual, post-efficiency performance — not a system padded to account for inefficiencies you're about to address.

Before Your SPM Assessment

It helps to gather your last 12 months of electric bills before your consultation. If you heat with gas, having those bills as well gives us a complete picture of your home's energy profile — including what a heat pump or geothermal system might change.

Frequently Asked Questions

Does SPM perform home energy audits?

SPM conducts a thorough energy assessment as part of the solar and home energy consultation process. We review your bills, evaluate your building, and identify efficiency opportunities before building any system recommendations. If a formal third-party audit is warranted for your situation, we'll say so.

How long does a home energy audit take?

A thorough audit with a blower door test and thermal imaging typically takes 2–4 hours, depending on the size and complexity of the home.

What does a home energy audit cost?

Costs vary. Some utility programs — including programs that have been available through ComEd — offer subsidized or free audits to qualifying customers. The availability and scope of these programs changes, so it's worth verifying directly with your utility what's currently available before paying out of pocket. Contact SPMor visit your utility's website for current program details.

Can I do a DIY energy audit?

You can do a basic self-assessment — checking for visible gaps around windows and doors, reviewing your utility bills for seasonal patterns, and noting areas that feel drafty or uncomfortable. But a DIY assessment won't find hidden insulation gaps or quantify your home's air leakage rate. For solar sizing purposes, the more accurate the efficiency data, the better the solar proposal will be.

Should I get an audit before or after getting solar quotes?

Ideally before — or at least simultaneously. If you get a solar quote based on your current usage and then make major efficiency improvements afterward, you may end up with a system larger than you need. SPM builds the efficiency evaluation into the solar consultation process so you don't have to sequence them separately.

Ready to see what your home's energy picture looks like? Start with a free assessment— we'll look at the full picture before recommending anything.