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This assumes you are licensed and insured for the work you are taking on. If you are not, that is the first thing to fix, and it is not what this article is about.
I worked the trade for about four years and I have not taken a side job in fifteen. I manage projects for a general contractor in Salt Lake now, so I see real bid numbers. Market numbers fluctuate from bid to bid, so these are mid-range for the work.
These figures are a good baseline for residential work. Commercial cannot be valued here. You need real quotes from supply houses and a firm grasp of what hours it is going to take to do a job. Additionally, you may need insulated duct. I am not sure you can get that off any shelf.
The numbers are Salt Lake in 2026. The arithmetic works anywhere — swap your own supply house prices and your own rate into it.
What do you charge to add a duct run on a side job?
On an open floor with no drywall in the way, about $200 to $300 per added diffuser. If it is all gypsum board and everything has to run through the attic, about $350 to $500 per run. Price by the register, not by the hour, until you know what an hour actually costs you.
Those are 2026 numbers where I work in Utah. Adjust for your market.
First, figure out what they are actually asking for
“Fix a run of duct” is usually the wrong description. Most of the time what somebody wants is a run added, because a room is not getting enough heat or enough cooling.
So before any number, understand what is actually wrong.
And ask the question nobody asks: is the furnace or the air conditioner equipped to handle the extra CFM? You can add all the duct you want. If the equipment cannot move the air, you have taken money to make somebody unhappy.
Look at the job before you say a number
I agreed to a side job once without going to see it.
When I got there, key details had been left out. Instructions I had given about outside air had not been followed. That job ended a friendship — I have not spoken to the guy in nine years.
Go look at it. Every time. There is no version of a side job where walking the space first makes things worse.
What actually goes into the price
At a minimum: labor, material, equipment. Unit rates or hourly rates.
I would suggest unit rates until you know what an hour costs you. Per-register pricing is forgiving while you are learning, because you are not exposed on the clock every time a job takes longer than you thought.
Here is what that looks like when it works. We were adding duct in a guy’s basement, paid per register. There were eight of them. We did seven in about two hours.
The last one was buried above a bulkhead and reaching it with the snips for the spin-in was impossible. I finally got it cut in with the uprights. Total time on the job was seven hours.
We went away with a fair shake and the owner was happy with the results. On an hourly bid, one of us was going to lose that day.
And do not forget the back end. I have been on the management side for about thirteen years and this is the part that everybody underprices — the time you spend estimating, ordering, driving, invoicing. You can capture it in a minimum hour fee, or you can bake it into the rate, but you have to capture it somewhere.
After everybody else is paid, you also need to get paid.
Once you have your number, you still have to hand it to somebody. I built a free estimate tool for tradespeople — no signup, no subscription: quickdrawinvoice.com
The costs that eat you
It is not the material. It is the inefficient time.
The third trip to the supply house. Taking a phone call at the top of a ladder and having to climb down. Not checking that you have every part and piece before you start.
None of that shows up on an invoice. All of it comes out of your day. Show up with the right tools and you cut most of it out before you start.
Where the line is on equipment
Adding duct is one thing. A new furnace or condenser is another.
Licensing rules for installing heating and cooling equipment vary by state, and that is worth knowing before you take the job, not after.
Refrigerant has its own rule on top of that. You need EPA Section 608 certification to buy and handle it, which means even if you set the equipment, you are not charging that system yourself. That is a wet-side job.
Find a company you trust and build a relationship. A partner you can call is worth more than the one job you turned down. Build relationships with a few of them and learn that side too. Then you do not have to rely on them — or you can, when you are swamped.
Knowing where your line is does not make you less of a tradesman. It is most of what makes you one.
Ask for money up front
I ask for material money before I start. On a furnace, fifty percent down. On added diffusers, twenty-five percent.
Say it factually and without embarrassment. It is going to cost money to get the material. That is not an awkward conversation unless you make it one.
“The last guy said he would do it for less”
Alright. Go with the last guy.
You have no idea what the other arrangement actually was, or what got left out of it, and you are not going to find out by bidding against a number somebody repeated to you.
I have been on the other side of this at my own house. I ask contractors for their best number. Then I call the high one back and tell him thanks, but I am going with somebody else — and he offers me a discount right there on the phone.
Which tells me one of two things. Either he did not price it fairly the first time, or he needs the work badly. Neither one earns a second look.
Price it right the first time and let the number stand.
When to walk away
Quitting is hard. There is probably a psychology class about why it eats at you.
Three reasons a job and I go separate ways.
The costs cannot be reconciled with the estimate.
Payment for work already in place has not come in a reasonable time. Put a payment clause in your estimate so this is a term and not an argument.
The personalities do not align. In my experience this almost always comes back to a misunderstanding about the terms of the agreement — which is another argument for getting it in writing.
Honestly, personality is the only one that has ever made me turn a job down.
What I learned underbidding my first one
My first side job, I bid it hourly. The owner bought the materials. I told him it should take about four hours at forty dollars an hour. This was years ago.
It took me ten.
I asked for four hundred dollars. We settled at one hundred sixty.
Here is what that taught me: when you give somebody an hourly estimate, they hear a price. Four hours at forty dollars is not an estimate to the customer, it is a hundred and sixty dollar job, and everything past that is your problem.
A different one went the other way. I cut in three ceiling diffusers in a neighbor’s basement and told him I would not charge him anything — we were neighbors. He felt like he should pay something, so he bought me two batteries for my drills. I came out ahead and he got a good deal.
Set a rate and stay firm. That is the whole lesson from both of them.
Work’s done? Here is how to bill.
Common Questions
How much should I charge to add a duct run?
About $200 to $300 per added diffuser on an open floor with nothing in the way, and about $350 to $500 per run when it is all gypsum board and the work is in the attic. 2026 numbers, my market. Use them as a starting point, not a price list.
If there are only two runs I go higher per run. If they are extremely long, I go higher. If there are more than four runs you will probably be fine at the lower number. Every job is different and every run is different.
Should I charge by the hour or by the job?
By the job, until you know what an hour costs you. Per-register pricing protects you while you are still learning how long things take. Hourly pricing on a side job turns your estimate into a cap.
Should I ask for money up front?
Yes, at least for material. Fifty percent on a furnace, twenty-five percent on added diffusers. Ask plainly. Material costs money before you ever pick up a tool.
What if the customer says someone else quoted less?
Tell him to go with the other guy. You do not know what was in that number and you are not going to find out. Price it right and let it stand.
Do I need a license to do HVAC side work?
That depends on your state and on what the work is, and it is worth finding out before you take the job. Equipment installation is a different question than adding duct, and refrigerant is its own question again — that one needs EPA 608 certification.