Why it is a real question
The outdoor unit has failed, the indoor equipment seems fine, and replacing half costs less than replacing all of it. That is a reasonable instinct and sometimes the right answer.
Why it is not always that simple
The outdoor condenser and the indoor coil are engineered and rated as a matched pair. Put a new outdoor unit with an old indoor coil and you frequently get neither the capacity nor the efficiency the new unit is rated for, having spent most of what a proper job costs.
When it works
- The indoor coil is relatively recent and in good condition.
- The refrigerant matches, so the equipment is genuinely compatible.
- The failure is clearly confined to the outdoor unit.
- There is no history of indoor coil leaks.
When it does not
- The indoor coil is old or has already leaked.
- The system uses an older refrigerant that current equipment is not designed for.
- The indoor equipment would need replacing soon anyway, meaning two jobs and two labour bills.
The refrigerant question
This is where most equipment-only plans come unstuck. Systems are designed for a specific refrigerant and they are not interchangeable. If your existing system runs an older refrigerant, matching new equipment to it is often not possible.
What we will tell you
Which situation you are actually in, including when the cheaper route is the right one.
Common questions
Can I replace only the outdoor AC unit?
Sometimes. It depends on whether the indoor coil is compatible and in good condition and whether the refrigerants match.
What happens if the units are mismatched?
You usually do not get the capacity or efficiency the new unit is rated for, and you have spent most of the cost of doing it properly.
Why does refrigerant type matter?
Equipment is designed for a specific refrigerant and they are not interchangeable. Older systems often cannot be matched to current equipment.
Is replacing half ever the right answer?
Yes, when the indoor coil is recent, compatible and in good condition, and the failure is clearly confined to the outdoor unit.
Reviewed and updated September 2026. Prices shown are owner supplied typical ranges, confirmed after an assessment. If anything here looks out of date, call (615) 400-4993 and tell us.