Temporary service pole at a construction site

Temporary Power for Construction: Design and Ontario Approvals

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Temporary power for a construction site in Ontario is normally delivered as a utility-connected temporary service, designed to the Ontario Electrical Safety Code (OESC), installed by a licensed electrical contractor, authorized by the Electrical Safety Authority (ESA) and connected by the local distributor. A generator is the alternative where the grid cannot reach the site in time. The schedule risk lies in the sequence of approvals and in load calculations done too late, not in the hardware.

This article sets out the options, the approval path, the code points that most often fail inspection, and the stage at which engineered design pays for itself. It is written for developers, general contractors, property managers and architects who must energize a site on schedule.

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TL;DR

  • Utility-connected temporary service is the most common arrangement for Ontario construction sites. Generators are used where the grid is unavailable or the timeline does not allow a connection.
  • Start the service request early: the utility needs site plans, electrical drawings, building permits and load calculations at the initial request stage.
  • Plans do not have to be submitted to ESA Plan Review for temporary installations at not more than 750 V phase-to-phase and 1000 A, but larger installations require submission before work starts.
  • Temporary wiring is held to the OESC like any other wiring: GFCI protection, no cable splices and equipment suited to the environment are routine inspection points.
  • A temporary service is typically approved for 12 months or less by Toronto Hydro, and ESA may re-inspect it after 6 months of use.

Table of Contents

What counts as temporary power on a construction project

Temporary power supplies tools, site offices, hoists, lighting, dewatering pumps and trailers during construction, renovation or a special event, and it is removed or replaced by the permanent service when the work ends. Two broad arrangements exist.

Utility-connected temporary service. A temporary service pole, cabinet or panel is connected to the distributor’s network. This is the arrangement most contractors expect on urban and suburban sites, and it provides stable capacity at a lower running cost than fuel-based generation.

Generator-based supply. Towable or skid-mounted generators serve remote sites, sites awaiting utility work, or short-duration loads. They are also used as a bridge while the utility connection is processed. Fuel logistics, noise limits, emissions and load-step performance must be assessed during design.

A third case is often overlooked: the permanent service, once energized, can feed the site before the building is complete. Whether that is possible depends on the stage of the permanent installation and on the approvals held, which is why the choice should be made during design rather than at mobilization.

What counts as temporary power on a construction project — overview diagram

The approval path for a utility-connected temporary service

The procedure differs slightly between distributors, but Ontario utilities follow the same logic. Toronto Hydro’s guide for temporary services on construction sites, special events and major renovations describes a structured process of ten steps. In summary:

  1. Submit a service request to the utility.
  2. Review the project details with the utility.
  3. Sign the job quote or offer and pay the fees.
  4. Complete the site construction.
  5. Obtain the ESA connection authorization.
  6. Pass the utility’s final site inspection before the grid connection.

The same guide states that connection for services of 750 V or less typically takes place within five business days once the ESA authorization has been received. That window should not be mistaken for the total lead time: the steps before authorization, particularly civil work, quotation and payment, usually determine the energization date.

Documents the utility asks for at the start

Customers submit site plans, electrical drawings, building permits and load calculations at the initial request stage, according to the same Toronto Hydro guide. A request submitted without a defensible demand estimate is the usual cause of an iterative exchange that costs weeks. Other distributors in Ontario publish their own requirements, and the point of supply should be confirmed with the distributor serving the site.

Site preparation before the utility arrives

Toronto Hydro’s guide requires that civil and electrical construction on the customer’s property be complete and safe before the utility crew attends. Clear, unobstructed access to the meter location is also required, and it is a frequent and avoidable cause of a failed visit. Where a structure houses or supports utility-owned equipment, the utility may require a stamped and signed structural analysis by a professional engineer, which can lengthen the schedule if it is requested late.

Clear access to a construction site meter cabinet

Why early consultation matters

The utility’s guidance emphasizes early consultation. Engaging the distributor late in site preparation, or determining the point of supply late, is a recognized cause of downtime. Early coordination with an engineering firm, so that load calculations and electrical designs are accurate, also reduces the risk of redesign and permit delay.

Plan review: when ESA submission is required

Rule 2-010 of the OESC governs the submission of plans to the ESA Plan Review Department. According to ESA’s bulletin on plans and specifications, plans and specifications need not be submitted for temporary installations operating at not more than 750 V phase-to-phase and not more than 1000 A. Larger and more complex installations must be submitted before electrical work begins.

The same bulletin lists the plan review triggers for permanent installations:

Installation Plans required
Three-phase consumer service 400 A or more
Single-phase consumer service 600 A or more
Feeders Above 1000 A

These thresholds matter on large projects. A mid-rise or a campus-style development may need temporary services above the exemption, and the permanent service for the same building will almost certainly require plan review. Coordinating both under one design avoids rework. Our guide to ESA plan review in Ontario covers the submission process in detail.

Connection authorization, duration and re-inspection

The ESA connection authorization is the document the utility needs before it energizes. The Ontario Amendments to the Canadian Electrical Code, Part 1 allow a connection authorization to be granted for a stated length of time and under specific conditions for a temporary installation, and to be renewed from time to time.

In practice, two durations apply on a Toronto Hydro service, according to its Conditions of Service, effective 1 January 2026:

  • Temporary connections for construction typically last 12 months or less. Extensions are reviewed case by case, and the service must be disconnected and removed once the period ends.
  • A connection authorization is valid for up to six months. If the connection is not completed, it may expire and a new authorization is needed. Temporary services may also be re-inspected by ESA once use exceeds six months.

For a project of 18 to 30 months, the consequence is that the temporary service needs a planned transition. Either an extension is requested well before the 12-month point, or the permanent service is energized in time to take over. Other distributors set their own terms, so the figures above should be read as the Toronto Hydro position and checked against the local utility.

Code requirements that decide inspection outcomes

Temporary wiring is not exempt from the OESC. It is exposed to moisture, vehicle traffic, impact and repeated relocation, so its failure modes are more severe than those of permanent wiring. The points below recur in ESA findings and in site audits.

Ground fault protection

ESA’s Flash 22-19-FL on extension cord safety is a useful reference for cord-related hazards. As summarized in our research, outdoor receptacles within 2.5 metres of grade require Class A GFCI protection. Specify GFCI protection at the distribution point or at the receptacle, and verify it by test, not by assumption.

Cable management

Splicing as a means of connecting cables is prohibited and is a frequent failure point. Cable runs should use listed connectors and appropriately rated flexible cord, supported clear of water and traffic. Temporary wiring should never be left in place as a permanent solution, because it is designed for limited duty.

Bonding, grounding and equipment suitability

Temporary distribution equipment must be rated for the enclosure type, ambient conditions and available fault current. Grounding electrodes and bonding must be verified after any relocation. These are design inputs, not field improvisations, and they are easier to correct on a drawing than at an inspection.

Worker safety obligations

Electrical safety on construction projects also falls under Ontario’s Occupational Health and Safety Act. O. Reg. 213/91, Construction Projects, contains the electrical provisions, and the Ministry of Labour’s page on achieving compliance on construction sites: electrical hazards notes that compliance with sections 181 and 183, which include isolating and de-energizing the system, would be considered reasonable precautions. The constructor and site supervisors carry the primary burden for site electrical safety, and the temporary system should be designed so that isolation points are accessible and labelled.

Sizing the temporary supply

Undersizing is the most common design error. Contractors tally the tools present on day one and forget the loads that arrive with later trades: tower crane or hoist motors, temporary heating and dehumidification, welding equipment, site trailers, lighting and, increasingly, EV charging for site vehicles and equipment.

A defensible sizing process proceeds as follows:

  1. Build a load schedule by construction phase, not for the whole project.
  2. Apply demand factors consistent with the OESC and identify the peak phase.
  3. Check motor starting currents, since hoists and large pumps govern voltage drop and breaker selection.
  4. Select the service voltage and size, and confirm that the choice stays within the exemption from plan submission, or plan for submission if it does not.
  5. Calculate voltage drop on the longest feeder to the work face and adjust conductor size or panel location accordingly.
  6. Document the results, because the utility will request the load calculations.

Where phased construction means the load grows over time, one option is to design the service for the peak and stage the distribution equipment. Another is to request a smaller initial service and apply for an upgrade. Our article on electrical service upgrades in Ontario explains the utility process for the second route.

Utility service or generator: a comparison

Criterion Utility-connected service Generator supply
Lead time Governed by utility quotation, ESA authorization and site readiness Short once equipment is available
Running cost Lower, metered energy Higher, fuel and servicing
Noise and emissions Negligible on site Present, may be restricted by municipal rules and site neighbours
Capacity Matches the service size requested Limited by unit size and paralleling
Best use Projects of several months or more Remote sites, bridging, short-duration loads

Many projects combine both: a generator bridges the weeks before the utility energizes, and then the service takes over. The design should show how the changeover is made safely, including the transfer arrangement if the generator remains as a backup. For standby and life-safety loads in the permanent building, see our emergency power design service.

Monitoring and maintenance during the project

Commissioning is not the end of responsibility. Technical Safety BC, the regulator in British Columbia, states in its temporary construction power permit guidance that the permit holder must appoint a competent person to monitor the site electrical system until decommissioning. That is a British Columbia rule, not an Ontario requirement, but it reflects a sound practice that Ontario constructors can adopt: name one person who inspects the system on a schedule, records findings and removes damaged cords and equipment from service.

A written inspection routine should cover GFCI test results, cord condition, enclosure integrity, grounding continuity and any changes to the load. Digital tools for tracking equipment condition, such as the approach described in this practical guide to condition monitoring, can help keep those records consistent across a large site.

Our perspective: design the temporary service as part of the project

In our experience across new builds and renovations in Ontario, temporary power is treated as a procurement item when it should be treated as a design item. The contractor orders a pole and a panel, the utility asks for load calculations and drawings that do not exist, and the energization date moves.

We approach it from the permanent design backward. The permanent electrical service, the construction phasing and the temporary service are one problem, because the point of supply, the meter location and the service size are set once. Where those decisions are made together, the temporary service often becomes the first stage of the permanent one, and the structural, civil and access requirements are met a single time.

We also recommend a short design package even where ESA plan review is not required. A load schedule by phase, a single-line diagram, a site layout showing the point of supply and distribution locations, and a transition plan to the permanent service are inexpensive compared with a lost week of site labour. Where a temporary service or its extension might exceed the exemption thresholds, the package should be ready for ESA submission from the start.

— Sanjay

Engineering support for temporary power

FutureGen Consulting Inc. provides temporary power design in Ontario for residential and commercial projects, including load calculations, distribution layouts and engineer-stamped drawings for utility and ESA submissions. The work links with our power distribution design, electrical construction cost estimation and construction review services, so that the temporary and permanent systems are coordinated. Our full list of services is on the services page. If your schedule depends on an energization date, contact us before the service request is filed.

Common mistakes to avoid

  • Requesting the service late. The utility process and civil work come before the five-business-day connection window, so start at design stage.
  • Submitting incomplete documentation. Site plans, drawings, permits and load calculations are required at the first request.
  • Ignoring the six-month and 12-month marks. Authorizations expire and extensions are reviewed individually.
  • Blocking meter access. The utility needs unobstructed access to the meter location.
  • Using splices and unprotected receptacles. Both are known inspection failures.
  • Leaving temporary wiring in service after the permanent supply is ready. It is not a permanent solution.

For wider background on the code framework, see our overview of the Ontario Electrical Safety Code.

FAQ

How long can temporary power stay in service on a construction site?

On Toronto Hydro’s system, temporary connections for construction typically last 12 months or less, and longer periods are reviewed case by case. The ESA connection authorization is valid for up to six months, and temporary services may be re-inspected after six months of use. Other utilities set their own limits, so confirm the term with the distributor serving the site.

Do temporary installations need ESA plan review?

Not when they operate at not more than 750 V phase-to-phase and not more than 1000 A, according to ESA’s plans and specifications bulletin. Above those limits, plans must be submitted to ESA Plan Review before electrical work starts. A licensed electrical contractor still files the notification of work and the installation is inspected.

What protection do outdoor receptacles on a construction site need?

Outdoor receptacles within 2.5 metres of grade require Class A GFCI protection. Cable splices are prohibited, and temporary wiring must be suited to the environment. Confirm the current rule text in the OESC and its Ontario amendments for your project.

Who is responsible for the temporary electrical system once it is energized?

In Ontario, the constructor and site supervisors carry the primary responsibility for electrical safety on the project under the Occupational Health and Safety Act and O. Reg. 213/91. Assigning a competent person to inspect the system on a schedule is good practice. Technical Safety BC makes this an explicit permit obligation in British Columbia.

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