AC Installation in O'Fallon, MO
A new air conditioner in O'Fallon will run from May through September every year. Tell us about the house, and a licensed contractor who covers St. Charles County will get in touch.
Tell us about the job
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Five months of real heat in O'Fallon
From May through September your air conditioner runs against afternoons that average 87°F. That is five months of steady work, not a few hot weeks here and there. A new system needs to hold up to that whole stretch, year after year.
O'Fallon has also seen 39 hail events and 84 damaging wind events over the past ten years, with hail as large as 4 inches. The outdoor unit sits through all of that, so it has to be installed and set in a spot that can take some weather along with the heat. Any new central air conditioner installed today also has to meet the federal minimum of 13.4 SEER2, so whatever goes in will meet that standard at least.
- 5 months
- May through September, your air conditioner is on duty
- 87°F
- the average summer afternoon it cools against
- 39 hail events
- in ten years, and hail bends the fins on outdoor coils
- 13.4 SEER2
- the federal minimum any new unit must meet
NOAA nClimDiv, 1991–2020 normals
A higher-efficiency unit would save about $40 a year to run in St. Charles County compared with a new unit at the federal minimum.
Estimates for a typical St. Charles County home, from EIA household energy data, Missouri fuel prices and NOAA climate normals. Your home will differ.
- What size air conditioner does my house need?
- The right size comes from a load calculation, not a chart based on square footage alone. A contractor looks at your insulation, your windows, your duct layout, and how much shade your house gets before landing on a number. An oversized unit cools the air fast but shuts off before it pulls the moisture out, so the house feels damp even at the right temperature. With summer afternoons here averaging 87°F for five months of the year, getting that size right matters more than it would somewhere cooler, since the system runs hard and often.
- Should I replace the whole system or just the outdoor unit?
- If your indoor coil and outdoor unit were matched when installed, replacing only the outdoor unit can throw off that match and hurt both efficiency and how well the system removes humidity. Refrigerant type is the other issue. Older systems use refrigerants that newer outdoor units are not built for, so a mismatch can mean the new unit cannot even connect to the old coil. A contractor can check what refrigerant your current system uses and whether the coil and unit still pair correctly before deciding which way to go.
- Do HVAC contractors in O'Fallon need a state license to work on my home?
- Yes, HVAC contractors doing this work need a state license. Ask to see the license number before any work starts, and check that it is current. A licensed contractor has also met requirements for handling refrigerant, which matters for anyone working on your air conditioner.