How to Price a Side Job — Adding a Duct Run or Register

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.

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.

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 or SEER requirements? 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. We built an estimating tool at quickdrawinvoice.com.

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.

another real story. We were adding some duct in a guys basement and he was paying us per register. There were 8 of them. we did 7 in about 2 hours. The last one was kind of buried above a bulk head gyp head and reaching it with the snips for the spin in was impossible. I finally got it cut in with the uprights. Total time was 7 hours. We went away with a fair shake and the owner was happy with the results.

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.

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.

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.

Knowing where your line is does not make you less of a tradesman. It is
most of what makes you one. Build a relationship with a few and learn that side to. Then you do not have to rely on them or you can when you are swamped.

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.

Common Questions

How much should I charge to add a duct run?

About $200 – $250 per added diffuser on an open floor with nothing in the way,
and about $350 – $400 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 two runs I go higher per run. If they are extremely long, I go the higher number. If there are more than 4 runs, you will probably be okay at the lower number but 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.