Office Container Power Requirements

Office Container Guide

Office Container Power Requirements

Every Bolted Box office container arrives job-ready, but it needs a power source before the lights, outlets, and climate control will run. Both the 20' and 40' office container use 120/240V single phase power. There are two ways to supply it, plus a few different ways it physically connects depending on how your specific container is built. This guide walks through all of it and keeps it simple.

Bolted Box office containers ship with lighting, outlets, and climate control already installed, ready to connect to power on delivery.

Land Power or Generator

You have two ways to bring power to the container, and both deliver the same 120/240V single phase service the office needs. We recommend land power for its stability and reliability, while a generator works as a solid backup when permanent service is not available.

Power requirement (both sizes): 120/240V single phase

Recommended: Land power through a temporary power pole wired into the breaker panel

Backup option: Generator rated at 15,000 watts for the 20' office or 20,000 watts for the 40' office

Our Recommendation

Go with land power whenever the site allows it. It draws from utility service, so it runs steady all day with no fuel to haul, no engine noise, and no load limits to manage. A generator absolutely works, but treat it as the backup plan, not the first choice. If you can get a temporary pole set on site, that is the route we recommend every time.

Recommended: Land Power

Land power is the option we recommend for both the 20' and 40' office container, and it is worth setting up whenever the site can support it. A licensed electrician sets a temporary power pole on site, then wires it into the container's breaker panel. Because it draws from utility service, land power stays steady and reliable, so you avoid the fuel, noise, and load limits that come with running a generator all day.

The connection still delivers 120/240V single phase power, and the wiring into the breaker panel should always be handled by a qualified electrician who can verify voltage, grounding, and conductor sizing before the panel is energized.

Backup Option: Generator Power

When land power is not available, a generator will run the office container as long as it is sized correctly. A generator that is too small is the most common cause of problems, so match the output to the container size and keep the service at 120/240V single phase.

20' Office Container

Minimum Generator

15,000Watts

120/240V • Single Phase • 60 Hz

40' Office Container

Minimum Generator

20,000Watts

120/240V • Single Phase • 60 Hz

Treat those numbers as a floor, not a target. A generator below them is the single most common cause of the problems in the troubleshooting section, so if anything, size up rather than down.

How Power Connects to Your Container

Every batch of office containers is built a little differently, so the exact spot where power connects depends on your unit. Your container will match one of the three setups below. The requirement is the same for all of them, 120/240V single phase, and any hard-wiring into a breaker panel should be done by a qualified electrician. Not sure which setup you have? Send us a photo and we will tell you.

Setup 1

Exterior Breaker Panel

Bolted Box office container exterior with the breaker box circled in red

The breaker box mounted on the outside of the container, circled in red.

Many containers have the breaker box mounted on the outside. An electrician wires land power or generator power straight into it from outside, so no cable pass-through is needed.

Setup 2

Interior Breaker Panel

Office container interior showing the breaker panel and the cable pass-through

An interior breaker box (circled red) with the exterior cable pass-through (circled green) used to route the wires inside.

Some containers have the breaker box inside. An electrician feeds the wires through the exterior cable pass-through, a small port low on the container wall, then runs them up to the panel inside. It takes an extra step, but it powers the container the same way.

Setup 3

Direct Generator Hookup

Office container direct temporary power hookup, a 50 amp twist-lock generator inlet

A 50-amp generator inlet built into the exterior wall. Some containers have this, but not many.

A few units have a 50-amp inlet built right into the outside wall. If yours does, a properly sized generator connects with a compatible cord and no hard-wiring, which makes it the quickest generator setup. Land power still wires into the breaker panel.

Safety Warnings

Power connections carry real risk, so review these points before anyone touches the panel. Improper connection can cause electrical shock, equipment damage, HVAC failure, or fire.

Only qualified personnel should connect power to the container.
Never connect a generator directly to utility power.
Generators must be properly grounded per the manufacturer's requirements and local codes.
Do not operate a generator indoors or in any enclosed area, and maintain adequate ventilation at all times.

Generator Connection Procedure

Follow these steps in order any time you connect a generator to the office container.

Verify equipment is off. Confirm the generator, the main breaker, and all branch breakers are OFF before you begin.
Position the generator outdoors. Place it in a well-ventilated area at least 20 feet from entrances, windows, and HVAC intakes.
Connect the feeder conductors. A qualified electrician connects the conductors to the breaker panel per applicable codes, routing them through the exterior cable pass-through if the panel is inside, then verifies voltage, grounding, and conductor sizing before energizing.
Start the generator. Start the engine and allow it to fully stabilize.
Turn on the main breaker. Once the generator is running steady, switch the main breaker ON.
Energize the branch circuits. Turn the circuits on one at a time, and energize the HVAC last. Wait at least 30 seconds after startup before turning the HVAC on.

Shutdown Procedure

When it is time to power down, reverse the process in this order.

Turn the HVAC off.
Turn off all branch breakers.
Turn off the main breaker.
Shut down the generator.
Disconnect the generator conductors.

Troubleshooting

Most issues trace back to an undersized generator or too much load on the circuit. Use this table to match the symptom to a likely cause.

Problem	Possible Cause
HVAC will not start	Generator is undersized
Lights dim during startup	Generator capacity too small
Breaker trips	Circuit overload
HVAC cycles improperly	Low voltage condition
Generator stalls	Excessive load

Additional Equipment Notice: Generator sizing covers the standard equipment installed at the factory only. Customer-supplied items such as refrigerators, microwaves, coffee makers, space heaters, power tools, and battery chargers may require a larger generator. Verify the total electrical load before operation.

Liability Disclaimer

This guide is provided for informational purposes only and is intended to assist qualified personnel in supplying temporary power to Bolted Box office containers.

All installations, connections, grounding, conductor sizing, and operating procedures must comply with all applicable federal, state, local, and site-specific electrical codes. Power connection and operation must be performed only by qualified personnel familiar with electrical systems and generator equipment.

Bolted Box LLC assumes no responsibility for injuries, property damage, equipment damage, code violations, or other damages resulting from improper installation, improper sizing, improper operation, unauthorized modifications, or the use of customer-supplied electrical equipment. It is the responsibility of the owner, dealer, installer, and operator to verify the power source is properly sized for the intended application.