The short answer
$125–$300
The transformer is the small box that steps house power down to the 24 volts your thermostat and controls run on. The part is inexpensive. What matters is why it failed, because a short in the wiring burns out a new one too.
Typical industry ranges for Western Washington — not a quote. Your exact price comes upfront, before any work starts, and you approve it first.
What moves the price
Why it failed
Transformers usually burn out from a short: a thermostat wire touching metal, a chafed wire to the outdoor unit, or a failed coil on the 24-volt side. Finding the short is part of the job.
Fuse or transformer
Many control boards have a small fuse that blows before the transformer does. Sometimes the fix is the short plus a new fuse, not a transformer.
The right size
It has to match your furnace’s supply voltage and be sized for everything on the control circuit. An undersized one runs hot and fails early.
Where it is
Most sit inside the furnace or air handler. On some systems it is in the outdoor unit, and access changes the time.
Thermostat dead and nothing runs?
A blown fuse or transformer is one of the first things we check. Exact price upfront.
Get My Upfront Quote60 seconds online · or call (253) 766-4822
Typical ranges at a glance
Typical industry ranges for Western Washington — not a quote. Your exact price comes upfront, before any work starts, and you approve it first.
Been told you need a new transformer?
A dead transformer is easy to confirm with a meter: house voltage going in, about 24 volts coming out. If it reads right, it is not the problem. If it burned out, the real question is what burned it, and we find that before fitting a new one.
We test it and show you the result before anything is replaced. If it tests fine, we say so.
Book a Second LookHow it works
- 1
Book online or call. Tell us what it’s doing, or what you were quoted. We diagnose it ourselves either way.
- 2
We test it and show you what we found. If the part tests fine, it isn’t the problem, and we tell you so.
- 3
You approve the exact price first. Nothing is replaced until you say go.
Where we work
From our base in Covington.
King County
Covington, Kent, Renton, Maple Valley, Black Diamond, Auburn, Enumclaw, Federal Way, Des Moines, Pacific, Algona, Burien, SeaTac, Tukwila, Issaquah, Newcastle, Snoqualmie, North Bend, South Seattle
Pierce County
Tacoma, Puyallup, Lakewood, Sumner, Bonney Lake, Lake Tapps, Orting, Buckley, Graham, Spanaway
Not on the list? Book it anyway and a technician confirms within 1 business hour.
Why homeowners call us
- You approve the price first. Exact price upfront, before any work starts.
- We answer 24/7. A technician reaches out within 1 business hour.
- 500+ jobs done by 4.9★ rated technicians. Licensed & insured.
- Fixed right, guaranteed. If it’s not right, we make it right.
Quick answers
What does an HVAC transformer do?
It steps the 120 or 240 volts at your furnace or air handler down to 24 volts. That low voltage powers the thermostat and tells the furnace and AC when to run. With no 24 volts, nothing answers the thermostat.
What are the signs of a bad transformer?
A thermostat that went blank (on systems that power it), a furnace and AC that will not respond, a control board with no light, a buzzing or burnt smell from the furnace, or a board fuse that keeps blowing.
Why did my transformer burn out?
Usually a short on the 24-volt side: a bare thermostat wire touching metal, a wire chewed or rubbed through on its way outside, or a failed part on the control circuit. A power surge can do it too.
My thermostat went blank right after I installed a new one. Is it the transformer?
Possibly. A loose wire touching the wall plate or cabinet during the swap is the most common way a working system goes dead. It often blows the board fuse first, which is cheaper to fix.
Can I replace it myself?
It is wired to house voltage inside the furnace, so power has to be off first. And a new one fails right away if the short is still there. Finding the short is the part worth paying for.
How long does the repair take?
Swapping the transformer is quick. Tracing the short that killed it is what takes time, and it is what stops the new one from failing.
How do I get my exact price?
Book online or call. A technician reaches out within 1 business hour, tests the part, and gives you the exact price before any work starts. You approve it first.
Ranges are for websites. Quotes are for you.
Book in 60 seconds — a tech reaches out within 1 business hour and your exact price comes before any work.
Get My Upfront Quote60 seconds online · or call (253) 766-4822
More from our site
Thermostat screen blank? · AC not turning on? · Thermostat problems · Control board cost · Furnace repair cost