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Temporary Site Trailer Electrical Load Calculator

Calculate the total connected electrical load and required amperage for a construction site office trailer's temporary power.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Required service amperage

29.17 A

Check your inputs

This is a simple connected-load sum with no demand factor applied — NEC Article 590 (Temporary Installations) governs the actual code requirements for temporary construction power, including conductor sizing, GFCI protection, and disconnect requirements, which this calculator does not address. Round up to the next standard breaker/service size and consult a licensed electrician for the actual installation.

Total connected load
7000 VA

With the figures above, the required service amperage comes to 29.2. Note that voltage (v) sits at the high end of the range this calculator was checked against, so treat the output as indicative rather than settled. The method behind this is well established, though site conditions and material batches will move it somewhat. This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

Add the equipment this sizes

This result is a specification — 29.167 A — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Total connected load (VA) = Lighting + HVAC + Receptacle Loads; Required amperage = Total VA ÷ Voltage — a straightforward connected-load sum with no demand factor applied (unlike a permanent dwelling service calculation), appropriate for a temporary construction trailer under NEC Article 590 (Temporary Installations), which governs the actual code requirements for temporary wiring.

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Frequently asked questions

Does this calculation apply a demand factor like a permanent dwelling load calculation?
No — it is a straightforward connected-load sum (lighting + HVAC + receptacle loads) with no demand factor applied, which is the appropriate approach for a temporary construction trailer under NEC Article 590 (Temporary Installations).
What amperage/breaker size should I actually install?
Round the calculated amperage up to the next standard breaker or service size, and always consult a licensed electrician — this calculator gives only the raw connected-load amperage and does not address conductor sizing, GFCI protection, or disconnect requirements, all of which NEC Article 590 governs for temporary installations.
Where do I get the VA values for lighting, HVAC, and receptacle loads?
Use the nameplate volt-amp (or watt) ratings on the trailer's lighting fixtures, air conditioner/heater, and any plugged-in equipment — sum each category separately before entering it here.