Flat rate works best for jobs you do often and can scope before you start: tune-ups, drain cleaning, part swaps, fixture replacements. Time and materials works best when you can't know the job until you open it up: hidden leaks, intermittent faults, older buildings, most commercial work. Most profitable shops run both, and decide job by job.
The argument over which one is "better" misses the point. The real question is who carries the risk of a job running long, and whether that risk is priced in.
The difference in one sentence each
Flat rate: the customer approves a fixed price for a defined job before you start. If it takes longer, you absorb it. If it goes faster, you keep the difference.
Time and materials (T&M): the customer pays for the hours worked plus parts. If it takes longer, they pay more. If it goes faster, they pay less.
Why customers lean toward flat rate
Homeowners want to know the number before the work starts. In a 2024 survey reported by ACHR News, 70% of homeowners said they were more likely to call an HVAC contractor who is transparent on pricing. A fixed price answers "how much is this going to cost me?" before the tech opens the toolbox.
It also takes the clock out of the room. On T&M, a homeowner watching a tech work is also watching the meter, and every trip to the truck feels like money.
Why some shops still prefer time and materials
The case for T&M is real, and it's worth hearing. Some plumbing companies argue that flat rate overcharges on easy jobs, because the price has to cover the hard version of the job too. They're not wrong. When a job goes smoothly, a T&M customer pays less.
T&M also protects you on jobs where the scope is a guess. Price a slab leak at a flat rate and you're betting your margin on what's under the concrete.
So the honest answer isn't "flat rate always". It's "flat rate when you can scope it".
Job by job: which model fits
| Job | Usually | Why |
|---|---|---|
| AC or furnace tune-up | Flat rate | Same checklist every time |
| Capacitor, contactor or igniter swap | Flat rate | Predictable time and part |
| Drain cleaning, secondary line | Flat rate | Predictable, with a note on access |
| Main line drain cleaning | Flat rate, "from $X" | The floor is predictable; length and access vary |
| Toilet rebuild, faucet swap | Flat rate | Repeatable |
| Water heater replacement | Flat-rate quote after a look | Scope is clear once you've seen the install |
| System replacement | Quote with options | Big ticket, and the customer's choice matters |
| No-cool or no-heat diagnosis | Flat diagnostic fee, then flat rate or a quote | You don't know the problem until you look |
| Leak behind a wall or under a slab | Diagnostic, then T&M or a quote | Scope unknown until opened |
| Intermittent electrical fault | T&M | Could be 20 minutes or a day |
| Commercial service call on contract | Often T&M | Contracts are usually written that way |
| Multi-stage project work | Estimate | Staged scope, staged billing |
Two patterns show up. First, the diagnostic fee is the bridge: it turns an unknown into a known, and the repair that follows can be flat rate. Second, the bigger and less predictable the job, the more it moves from a flat price to a quote. For staged project work, that means a proper estimate. On Enterprise, that's what work order estimates are for.
How to switch without betting the business
If you're 100% T&M today, don't flip everything at once.
- Pick your top 10 repeatable jobs. The ones you'd do in your sleep.
- Price them properly. Loaded labor cost, parts at cost, priced to a margin. Here's the step-by-step.
- Run them for a month and track actual time. If a job keeps running long, the price is wrong, not the tech.
- Keep T&M for everything else. Expand the flat-rate list as the data comes in.
- Say how you bill travel. Flat rate or not, customers hate a surprise trip charge. How to charge for travel time compares the options.
What flat rate changes for your techs
Owners usually think about flat rate as a pricing decision. Techs feel it as a change to their day, and it's worth thinking through before you switch.
On T&M, a slow job costs the customer. On flat rate, it costs you. That changes what "a good day" means. A tech who's quick and careful now makes the shop more money on every call, and a tech who takes the long way around a job shows up in your numbers faster. If you pay any kind of commission or bonus, make sure it rewards finishing the job right the first time, not rushing it. A callback on a flat-rate job is pure cost.
It also changes the conversation at the door. Instead of "it depends how long it takes", your tech can say "that's $X, and it includes this". Most techs find that easier, not harder. There's no meter running and no arguing over time. But they need the price in front of them. If they're reading it off a sheet from two years ago, or guessing, you're back to every tech charging their own number.
Give them the list, tell them what's included in each job, and let them quote from it.
What makes flat rate fail
Stale prices. A flat rate set two years ago on last year's part costs quietly loses money on every ticket. Put a review date on the calendar.
Two techs, two prices. If the price lives in each tech's head or on a laminated sheet, it isn't flat rate. It's whatever that tech charges. The price has to come from one list.
No scope line. "Water heater replacement: $X" invites an argument when the flue needs replacing too. One line on what's included heads it off.
Flat-rating the unknowable. If you can't scope it, don't fix the price. Charge for the diagnosis and quote from there.
Keeping both models in one place
Running a mix is normal. What causes trouble is running it from four lists. When flat-rate services and hourly labor sit side by side in one price list, the office can quote a flat-rate repair and add hourly labor for the extra work on the same quote, without anyone inventing a number.
The FSM Navigator pricebook holds both: services at a fixed price, labor by the hour, and materials with a part number and unit. Your quotes and your online booking page read from it, and a service can bring the materials it always uses along with it. It's part of the one app you run the work in, from booking request to invoice, and it's included in Pro, which you can try free for 14 days.
FAQ
Is flat rate or hourly better for plumbers?
Both, depending on the job. Flat rate suits repeatable work like drain cleaning and fixture swaps. Hourly or diagnostic-first suits hidden leaks and older systems where the scope is unknown.
Can I use flat rate and time and materials on the same job?
Usually yes. A flat-rate repair plus extra hourly labor for something you found on site is common. Say so on the quote first.
Does flat rate mean I charge more?
Not necessarily. It means you charge the same for the same job. Whether that's more depends on how you priced it.
What about diagnostic fees?
A flat diagnostic fee is the most common bridge between the two models. Many shops credit it toward the repair if the customer goes ahead.