5 
12 *The Angi rating for Energy Efficiency Auditing companies in O Fallon, IL is a rating based on verified reviews from our community of homeowners who have used these pros to meet their Energy Efficiency Auditing needs.
*The HomeAdvisor rating for Energy Efficiency Auditing companies in O Fallon, IL is a rating based on verified reviews from our community of homeowners who have used these pros to meet their Energy Efficiency Auditing needs.
Last update on July 30, 2026
Serving O Fallon, IL and surrounding areas
In business since 2001
Free estimates
Credit card accepted
"St. Louis Insulation did a great job. Zac and his team were great to work with and they cleaned up after their work was completed. We were very happy with the project results and highly recommend St. Louis Insulation."
+40
Serving O Fallon, IL and surrounding areas
In business since 1978
"Paul Peterson is a knowledgeable and friendly guy.? Arrived at my house 15 min. prior to apt time.? Paul reviewed the areas I thought were the worst, and showed me leaks in the house I would never have thought of.? I was not surprised at the outcome of the energy audit, but I was surprised by the price.? It was less than I thought it would've been."
Serving O Fallon, IL and surrounding areas
In business since 2022
Free estimates
Credit card accepted
"They are in the process of sending out an engineer"
+3
Serving O Fallon, IL and surrounding areas
In business since 1971
Emergency services offered
Credit card accepted
"My experience with the Spengler Company was great. Colby arrived at my house on time and then proceeded to perform the cleaning of my air conditioning unit. He found that our refrigerant was low so he filled that up. And he also changed our air filter for FREE! He then gave me six options to replace the water heater in our home. It was over 20 years old and had been leaking on the floor. We selected the second option and he called it in and our water heater was changed out the same day! WOW. What service! We couldn't be happier.
"
Serving O Fallon, IL and surrounding areas
In business since 2009
Free estimates
DelVon Hardaway is the professional you are looking for when a home or business energy analysis is required. More and more this is becoming a valuable tool across the country. Everyone needs a current energy audit, so do not hesitate to call DelVon Hardaway for your energy savings analysis.
Serving O Fallon, IL and surrounding areas
In business since 1990
Emergency services offered
Credit card accepted
"Excellent. Eddie Givens, the owner of the company, personally fixed our AC unit. All of his HVAC technicians were working today. Eddie offers a wealth of services. We plan to next use him for an electrical project and replacing our current HVAC contractor with twice annual check ups. We strongly recommend Eddie Givens"
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