HVAC Change Orders: Don't Let This Eat Your Margin

Nobody sets out to work for free. But if you run HVAC, you probably do it a few times a year without noticing. The GC asks you to shift the air handler six feet because the plumber got there first. The homeowner decides they want a mini-split in the sunroom while your guys are already on site. The framer boxed in a chase that will not take your trunk line. You handle it, because that is what good mechanical contractors do. Then you invoice at the end of the job, and the payment that comes back is the original contract amount.

That is the whole problem with the HVAC change order. The work is real, the cost is real, but the paperwork never happened — so as far as the person holding the checkbook is concerned, it was included. This post walks through what that actually costs you, the specific mistakes that cause it, and two free ways to stop the bleeding.

What one unpapered HVAC change order really costs

HVAC changes are expensive out of proportion to how small they look. A relocated condenser is not just a condenser. It is a new line set, more refrigerant, a different pad, possibly a longer electrical run, and a return trip for a tech who was supposed to be on another job that afternoon. Call it a modest one: eight hours of labor and $900 in material.

Now run the math on eating it. If you work on a 12% net margin, absorbing $2,000 of unpaid work means you need roughly $16,000 of additional revenue just to get back to where you were before you helped somebody out. That is another job. Possibly a month of selling. All of it caused by a two-minute conversation in a driveway that nobody wrote down.

And the direct cost is only the first bill. The rest shows up later:

• The schedule slips and it is your fault on paper. Nothing documents why you were on site an extra day, so the delay reads as an HVAC delay.
• Your crew burns hours that were sold to another customer. The next job starts late, and that customer starts calling.
• Retainage gets harder to chase. A GC who disputes your final number has a reason to sit on the last 10%.
• The relationship sours. You feel used, they feel gouged, and neither of you has a document to point at.
• Your warranty exposure grows quietly. Equipment installed in a location you did not design for is equipment you will be back to service.

None of that is dramatic. That is exactly why it keeps happening. There is no single catastrophic day — just a slow leak in your margin that shows up at the end of the year as a number smaller than it should be.

Five HVAC change order mistakes that eat margin

1. Taking the change verbally because you are already on the roof

This is the big one. The super asks, you nod, your tech does it. Three weeks later the super has moved to another project and the office has no record of the request. Verbal agreements are not worthless, but they are worth exactly as much as the other party is willing to remember. When money is tight at closeout, memories get short.

Cost: the full value of the work, most of the time. If you cannot show what was asked and what was agreed, you are negotiating from zero.

2. Pricing equipment and forgetting everything around it

HVAC contractors are usually good at quoting a unit and bad at quoting the consequences of moving it. A change that adds two supply runs also adds balancing time, possibly a larger blower, extra insulation, more fasteners, and a second trip for the commissioning tech. Quote the unit, eat the rest.

Cost: typically 20–40% of the true change cost, invisible because it is buried in labor you never tracked separately.

3. Leaving markup and overhead off the change order entirely

Plenty of guys price a change at cost plus a token 10% because it feels awkward to charge full margin on a favor. But a change order carries more overhead per dollar than base contract work — it interrupts the schedule, it requires re-planning, and it usually comes with a rush. If your contract allows markup on changes, use it. If it does not say, that is a conversation to have before the job, not after.

4. Doing the work first and pricing it later

Once the ductwork is in the ceiling, your leverage is gone. Nobody negotiates hard for a price on work that is already finished and cannot be un-finished. Price before you cut metal, every time, even if it means a one-day pause.

5. Sending a change order and never getting it signed

An emailed PDF sitting unopened in a homeowner’s inbox is not an approval. It is a document you will wave around later while the other side says they never agreed to it. A change order only protects you when somebody put their name on it before the work started. If you want the full picture on that, we wrote about the risks of unsigned change orders separately.

The T&M trap on HVAC service changes

Service and retrofit work invites time-and-materials handling: “we will just track the hours.” That is fine when both sides agree in writing on the rate, the markup on parts, and a not-to-exceed number. It is a nightmare when they do not, because the customer’s idea of a reasonable number and your timesheet rarely match.

If you run a change as T&M, still issue a change order. Write the scope, write the hourly rate, write the material markup, write the cap, and get a signature before the first hour is logged. A signed T&M authorization is a change order — it just has a variable dollar figure instead of a fixed one.

The fix, two ways — and both are free

You do not need a $200-a-month platform to solve this. You need every change written down and signed before work starts. There are two ways to do that, and which one is right depends on how you like to work.

If you want a spreadsheet: use the free Excel change order template. It is a proper HVAC-friendly change order form — line items for equipment, material and labor, automatic markup and tax, and a revised contract value that calculates itself so you never send a number that does not add up. It also includes a change order log so you can see every change on the job on one tab. Fill it in at the truck, print or PDF it, get it signed on site. No account, no subscription, no catch.

If you would rather not touch a spreadsheet: the free digital change order tool does the same job from your phone. Type the change, hit send, and your GC or homeowner signs it on their screen in about thirty seconds — while they are still standing in the mechanical room and still agree the change is necessary. Every change order is stored, timestamped, and attached to the project, and the contract total updates itself as approvals come in. Same price as the spreadsheet: free.

Two different habits, same outcome: nothing gets installed until somebody has agreed in writing what it costs. If you are wondering how a tool like this can cost nothing, we explain it on the pricing page.

The 60-second HVAC change order checklist

Run this before your crew touches anything that was not on the approved drawings:

1. Name the trigger. Who asked, when, and why — owner request, plan conflict, field condition, or code inspector.
2. Describe the scope in mechanical terms. “Relocate 3-ton condenser 14 ft north, add 16 ft line set, new pad, extend disconnect” — not “move outdoor unit.”
3. Price all four buckets. Equipment, material, labor hours, and subcontracted work (crane, electrical, patching).
4. Add markup and tax at your contract rate.
5. State the schedule impact. “Adds 1.5 days to mechanical rough-in” protects you later far more than the dollar figure does.
6. Show the revised contract total, not just the change amount. It kills the closeout argument before it starts.
7. Get a signature before work begins. On paper, on a phone, either way — but before.

The whole thing takes about a minute with a template in front of you. Compare that to a minute against $2,000 of unpaid work, and it is the best-paying minute of your day.

Residential vs. commercial HVAC changes

On residential work, the pressure is emotional. The homeowner is standing right there, they are excited about the sunroom, and saying “let me price that first” feels like being difficult. It is not. It is the single kindest thing you can do, because the alternative is an argument at final invoice with somebody who genuinely believed it was included.

On commercial work, the pressure is procedural. There is a change order clause in your subcontract, there is a submission deadline, and if you miss it you may have waived the claim regardless of how obviously the work was extra. Read your contract before the job starts and find out how many days you have and who has authority to approve. A super who says “go ahead” is often not that person — on most projects only the GC’s project manager or the owner can bind the change.

This is general information, not legal advice. Contract terms and state requirements vary and change — confirm the rules that apply to you with your state’s licensing board or a licensed attorney before relying on them.

Start with the next change, not the whole system

You do not have to fix your whole process this week. Pick the next change that comes up — the next duct conflict, the next “while you are here” request — and write it down before you do it. One job of doing that consistently and you will see exactly how much you have been giving away.

Grab the free change order spreadsheet if you like paper and formulas, or create a change order online if you would rather send it from the van. More on the trade side of this in our change order blog, including the plumbing version of this same problem.

Frequently asked questions

What should an HVAC change order include?

At minimum: the project and change order number, the date, who requested the change and why, a scope description in mechanical terms (equipment, duct, refrigerant line, electrical), a priced breakdown of equipment, material, labor and subcontracted work, your markup and tax, the schedule impact in days, the revised contract total, and signature lines for both parties. The free Excel change order template already lays all of that out and calculates the totals for you.

Can I charge markup on an HVAC change order?

Usually yes, but it depends on your contract. Many subcontracts and residential agreements specify an allowable markup percentage on changes, and some cap it. Check that language before the job starts. If your contract is silent, agree a markup rate with the GC or homeowner up front rather than arguing about it at closeout, because change work carries more overhead per dollar than base contract work.

Is a verbal approval from the site super enough?

It is a risk. Two things can go wrong: the super may not have authority to bind the change, and memories of a driveway conversation get very short when money is tight at the end of a job. Treat a verbal go-ahead as permission to price the change, not permission to install it. Send a written change order the same day and get it signed before your crew starts.

Is the free Excel change order template really free?

Yes. Download it, use it on every project, edit it however you like — there is no account required and no cost. If you would rather not open a spreadsheet on site, the digital version is free too and lets your client sign from their phone.

Daisy Porter

Co-Founder, ChangeOrdersPro

Daisy writes about the unglamorous side of running a build — the paperwork, the change orders, and the conversations that keep a job profitable. ChangeOrdersPro is the free tool her team built so contractors can send a professional change order and get it signed from a phone in about 30 seconds.