A day without site power rarely costs one day. It stops the trades that need electricity that day, and it also pushes the trades waiting behind them, which is how a short outage turns into a schedule problem. The loss shows up as idle crews, rescheduled inspections and re-sequenced deliveries, none of which appear on an invoice labeled "outage." This page walks through what stops, what compounds, and how to put a number on it using your own figures.
Lighting is the first thing to go and one of the first things that halts work. OSHA’s 1926.56 illumination standard requires construction areas, corridors and other work spaces to be lit to minimum levels, so a crew cannot simply carry on in the dark. Interior work, in particular, tends to stop when lighting fails.
What stops first, and what stops next
Not every task halts at once, which is why the first hour of an outage can look manageable. Tools that plug into the grid stop immediately, and anything needing light stops with them. Work that does not need power, such as hauling material, may continue for a while. The trouble starts when those tasks run out of things to do and the crew has no alternative.
The second-order effects come from dependency. A trade that cannot finish its work leaves the next trade without a clear area, and that trade’s start moves with it. Two or three trades can stack up behind one stalled task. By the time power returns, the site has a queue instead of a single missed day.
Where the cost sits
The cost of a stoppage spreads across several budget lines, which is why it is easy to undercount. The table below separates the lines so each can be priced from your own records. It deliberately holds no dollar figures, since labor rates, general conditions and contract terms differ on every commercial job.
| Cost line | What drives it | Where to find your number |
|---|---|---|
| Idle labor | Crew size and hours paid while work is stopped | Daily labor report |
| Rescheduled trades | Fees or re-mobilization when a sub must return | Subcontract terms |
| Extended general conditions | Each added day of site overhead | General conditions budget |
| Inspection and delivery slots | Rebooking after a missed window | Inspector and supplier calendars |
| Schedule exposure | Liquidated damages or a delayed handover | Prime contract |
Pricing a day yourself
A simple worksheet turns that table into one figure for a day of stoppage. Add the idle labor, any re-mobilization, the daily general conditions and any contract exposure per day of delay. Then compare the total with the rental cost of a standby or primary generator for the same period. The comparison is the useful part, because it shows whether temporary power is a cost or a hedge on this particular job.
The pricing guide explains what drives generator rental cost, and the sizing guide helps you list the loads you would need to cover. Neither gives you a stoppage figure, since that comes from your own contract and crew data. Use them for the other side of the comparison. For the bid side of the same question, see how a temporary power line item is written into a commercial bid.
Ways to reduce the exposure
The list below covers common ways to limit how much a power failure can cost. Not every one fits every project, and each carries its own cost. Pick the ones that match your schedule risk. Matching the unit to each project phase is another option, and our page on how temporary power changes from slab to punch list shows how the load shifts along the way.
- Keep a generator staged for the loads that cannot stop, such as lighting and critical tools
- Separate the loads that must run from those that can wait, so a smaller unit covers the first group
- Confirm refueling arrangements before an extended run, not during one
- Agree in advance who authorizes a rental when power fails, so the decision does not wait on a phone tree
- Review the schedule for the points where one stalled trade blocks the most others
For options on holding fuel on site, see our page on rental fuel tanks. A larger tank reduces how often a truck must reach the unit, which matters on a site with tight access.
Talking to a rental team about standby
Stag Power Rentals supplies diesel generators from 20 kW to 2000 kW out of its Dickinson, TX yard. If you are weighing a standby unit against the cost of a stoppage, bring your load list, voltage and the schedule points you are most worried about. For how we support commercial and other construction work, see our construction power overview, and when you have your numbers, request a quote.
Frequently Asked Questions
What does a day without power cost a commercial project?
The figure depends on your crew size, subcontract terms, general conditions and contract exposure, so no single number applies. Price it from your own records using the cost lines above. The comparison with generator rental cost then shows whether coverage is worth carrying.
Why does a short outage delay more than one day?
Trades depend on each other. When one cannot finish, the next cannot start, and several can stack up behind the first. The delay then outlasts the outage itself.
Does lighting alone stop work during an outage?
Often, yes. OSHA 1926.56 sets minimum lighting levels for construction areas, so interior work generally cannot continue in the dark. Outdoor work in daylight may carry on longer, depending on what it needs.
Should I rent a generator before an outage or after one?
That depends on how costly a stoppage would be on your schedule. If a single lost day sets back a handover or triggers contract exposure, having a unit ready may make sense. If the schedule has float, waiting may be acceptable.
What should I send with a quote request for standby power?
Send the loads you need to protect, voltage, expected run time and site access details. If you have a schedule, point out the activities that would hurt most if they stopped. That lets the rental team size and stage the right unit.