Mini Split 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.
Tell us about the job
It takes about a minute.
A mini-split here works most of the year
O'Fallon needs heat or cooling every month of the year, seven months of heat and five of cooling. On winter nights that average 25°F, a mini-split's heat pump has to keep working instead of handing off to a furnace, and on summer afternoons that average 87°F it runs the other direction. That's the load a new unit has to carry, in both directions, for the full year.
Any mini-split installed new has to meet the federal minimum for a split-system heat pump, 14.3 SEER2 for cooling and 7.5 HSPF2 for heating. That's the floor, not a special ductless rule. St. Charles County also sees its share of winter storms and damaging wind, and with close to a fifth of Missouri households losing power for a day or more last year, it's worth asking any contractor how the system you choose holds up when the power drops on a 25°F night.
- 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
- Is a mini split worth it?
- For the right room or space, yes. A mini split heats and cools without ducts, so it works well for an addition, a garage, or a room that never feels right on the main system. O'Fallon homes need heat from October through April and cooling from May through September, so the unit runs most of the year rather than sitting idle. Whether it makes sense for your house depends on what you're trying to fix, and a contractor can look at the space and tell you if it's the right call.
- How many rooms can a mini split cover?
- A single outdoor unit can run one indoor head or several, depending on the system. Each indoor head is sized for the room it serves, so the number of rooms it can cover comes down to matching the right head size to each space and keeping the total within what the outdoor unit can support. A contractor can work out how many zones your home needs and where each head should go.
- Can a mini split heat a whole house?
- It can, if the system is sized and laid out for the whole house rather than for one or two rooms. That means an outdoor unit paired with enough indoor heads to reach every room, sized for winter nights that average 25°F here. A mini split heat pump also has to meet the federal minimum of 7.5 HSPF2 for heating, so a modern unit is built to handle real cold. Whether it can carry your house through the winter without backup heat is something a contractor needs to size for your specific home.