HVAC Installation in O'Fallon, MO
A new system here will heat from October through April and cool from May through September every year. Tell us about the house, and a licensed contractor who covers St. Charles County will get in touch.
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A system that works almost every month here
O'Fallon needs heat from October through April and cooling from May through September. That's 12 months of the year with the furnace or the air conditioner running, and only a short stretch in between when neither one has to. Winter nights average 25°F, so a new furnace needs to hold up to months of hard, repeated cycling. Summer afternoons average 87°F, so the air conditioner is doing real work most days from May through September too.
Most homes here heat with gas, and whatever you install has to meet the federal efficiency minimum for this region. St. Charles County has also seen 9 winter storms and 84 damaging wind events over the past ten years, and close to a fifth of Missouri households lost power for at least 24 hours in 2024. That's worth knowing when you're deciding what to install and how it should be set up.
- 7 months
- October through April, your system heats
- 5 months
- May through September, it cools
- 25°F
- the average winter night it heats against
- 87°F
- the average summer afternoon it cools against
NOAA nClimDiv, 1991–2020 normals
- When should I replace my HVAC system?
- Replace it when repairs start costing more and coming more often, or when a contractor finds something like a cracked heat exchanger or a refrigerant leak that costs more to fix than the unit is worth. Age matters too. Homes here need heat from October through April and cooling from May through September, so the system runs nearly all year with little downtime to rest. If yours is getting old and needs a repair, ask the contractor whether that money is better spent on a new system.
- Should I replace my furnace and air conditioner at the same time?
- If both are old, replacing them together usually makes sense, but it depends on the condition of each one. A furnace and air conditioner installed at the same time are matched to work together, and pairing a new unit with a much older one can mean the older piece drags down the performance of the new one. They also share the same ductwork and, in many systems, the same coil cabinet, so a contractor can size both correctly when installing at once. If only one has actually failed, a contractor can tell you whether it is worth waiting on the other.
- What happens during an HVAC installation?
- A contractor first sizes the equipment to the house, since a furnace or air conditioner that is too big or too small will not heat or cool evenly. On install day, the old equipment comes out and the new furnace, air conditioner, or both go in, along with any duct or electrical work the new system needs. The refrigerant lines get connected and checked for leaks, the gas or electrical connections are tied in, and the system gets tested through a full heating and cooling cycle before the contractor walks you through it. Homes here need heat or cooling every month of the year, so getting this right the first time matters.