BTU SizerWhen will each unit need replacing?
Everything in the house has a date on which it stops being maintenance and starts being a purchase. Most people find out on the coldest night.
One comfort check a month
MonthlyOne thing a month worth measuring, cleaning or switching over before the weather turns — the maintenance side of sizing, in two sentences. No product pitches.
Free to use — Pro is for keeping it
This tool, like every other one here, is free and needs no account. A free account keeps three setups and three email alerts. Pro takes the ads off every site we run and lifts that to 200 setups and 50 alerts, adds a public page for any result and lets you embed the tool without our badge.
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How this works
How long equipment lasts
Typical service lives, which is what turns an install date into a planning date.
| Equipment | Typical life | Plan from |
|---|---|---|
| Air conditioner or heat pump | 12–17 years | Year 12 |
| Gas furnace | 15–25 years | Year 15 |
| Water heater, tank | 8–12 years | Year 8 |
| Mini split | 12–20 years | Year 12 |
| Ductwork | 20–30 years | When the system changes |
Replacing on a plan costs less than replacing in an emergency, because an emergency has no time to compare quotes.
Frequently asked questions
How long does an air conditioner last?
Twelve to seventeen years for a well-maintained residential system, less in coastal salt air and more in a mild climate. A furnace commonly reaches fifteen to twenty-five. Neither fails on a schedule, which is why the planning horizon matters more than the exact number.
Is it worth replacing before it fails?
Once a unit is past its expected life and needs a repair worth more than a few hundred, usually yes. Efficiency has improved enough that a fifteen-year-old system typically costs noticeably more to run than a current one, so the replacement is partly paid for by the bill.
How do I find the install date?
The serial number on the data plate usually encodes the manufacturing year, and most manufacturers publish the format. Failing that, a service sticker inside the cabinet or the house records.