A power dip costs the time to recover plus whatever the interruption does to the surface. On a polished concrete job, a stalled grinder or a collector that drops out mid-pass can leave the crew stopping, restarting and checking the work. The cost is rarely the dip itself. It is the minutes or hours of work that follow, multiplied across a crew paid by the hour.
Dust control makes a dip more than an inconvenience. OSHA’s 1926.1153 silica standard calls for dust collection or water delivery when grinding concrete, so a collector that loses power can force the crew to stop grinding until it is running again. That turns a short fluctuation into a work stoppage.
What a dip does to the work
A dip can show up in several ways, and the effect depends on the equipment and the moment. A grinder may slow or stall, a collector may shut off, and a controller may reset. The crew then has to restart, and on a surface where consistent passes matter, they may need to inspect the area before continuing. Whether a given dip leaves a mark on the finish depends on the equipment and the stage, so the crew’s own judgment decides what needs rework.
Repeated dips cost more than a single one, because each carries its own restart and check. A generator that cannot hold voltage under the grinder’s startup load can produce a pattern of small interruptions across a shift. A crew often accepts those as normal until someone adds up the lost time.
Where the cost sits
The table below separates the cost of a dip into lines a crew lead or estimator can price from their own records. It carries no dollar figures, since labor rates, equipment and contract terms differ by job.
| Cost line | What drives it | Where to find your number |
|---|---|---|
| Lost crew time | Minutes to restart, inspect and resume, times crew size | Daily labor and time records |
| Rework | Area that must be re-passed or re-checked after an interruption | Foreman’s notes and job photos |
| Schedule slip | Added days that push the finish or the next trade | Project schedule |
| Equipment wear | Repeated stalls and restarts on motors | Maintenance records |
| Customer or GC impact | Missed handover or reputational cost | Contract and customer correspondence |
Pricing one bad day
A simple way to see the cost is to take a shift with several dips and add up the time. Count the minutes lost to each restart and check, multiply by the crew, and add any rework. Then compare the total with what it would cost to run a unit sized for the load with headroom. The comparison shows whether the problem is the generator or the plan.
If dips come from startup surges, the fix is often in the sizing, not in buying more capacity than you need. The construction generator sizing guide explains how to build a load list with startup headroom, and the rental pricing guide covers what drives cost on the other side. The page on common generator sizing mistakes for grinders covers startup draw and the dust collector load in more detail. Who is responsible for supplying the power in the first place is covered in who supplies power on a prep subcontract.
Ways to reduce the chance of a dip
The list below covers common approaches. Which ones fit depends on your equipment and your site, and each has its own cost.
- Size the generator for the simultaneous load plus the largest startup
- Stagger the startup of the grinder and the collector
- Keep cable runs short and use the right gauge for the distance
- Avoid sharing the generator with unrelated loads that cycle on and off
- Log dips and their causes, so repeated ones point to a fix
For a wider view of powering a grinding crew, see our page on concrete surface prep power.
Talking to Stag about a steady supply
Stag Power Rentals supplies diesel generators from 20 kW to 2000 kW out of its Dickinson, TX yard. Bring your equipment list, voltage and the symptoms you have seen, and the team can help check whether the issue is size, startup or layout. For the broader picture, see our construction power overview, and when you are ready, request a quote.
Frequently Asked Questions
Can a power dip damage a polished concrete floor?
It can affect the work if the equipment stalls or the pass is interrupted, though the effect depends on the equipment and the stage. The crew’s own inspection decides what needs rework. A steadier supply reduces how often the question comes up.
Why does a dip stop the job if only the collector loses power?
Grinding concrete generates dust, and OSHA 1926.1153 calls for dust collection or water delivery. If the collector stops, the crew may need to stop grinding until it runs again.
How do I know if dips come from the generator or something else?
Log when they happen and what was starting or running. Dips at startup often point to sizing or startup stacking. Dips after a long run may point to fuel, cabling or a separate fault.
Is a bigger generator always the fix?
Not always. A unit sized to the simultaneous load with startup headroom often solves the problem. A much larger unit costs more and may run lightly most of the time.
What should I send with a quote request?
Send the equipment list with voltage and amps, the symptoms and when they occur, run hours and cable distance. That lets the rental team size a unit that fits the load.