Quick Answer: Pick 60A for a single-occupant container lunchroom or basic jobsite shack with one mini-split and a few outlets. Choose 100A for a full container office with multi-zone HVAC, kitchenette appliances, a plotter, and EV charging headroom. CEC Section 8 demand factors drive the call in Ontario, not guesswork. Van Blanc has supplied containers across Ontario since 1995. Honest 4.9-star service, 1 to 3 day delivery from 4 Brantford yards.
In This Guide
- Should You Run 60A Or 100A To A Container Office In Ontario?
- How Does CEC Section 8 Size A Container Office Service In Ontario?
- The Load-Calc Worksheet We Walk Through With Every Buyer
- When 60A Is Honestly Enough: Three Real Container Setups
- When 100A Is The Right Call: Full Office, Multi-HVAC, Appliances
- What Wire Gauge And Conduit Size Does A Container Office Feed Need?
- How Much More Does 100A Cost Than 60A For A Container Office?
- Future-Proofing For EV Charging And Heat Pumps
- How The ESA Connection Authorization Flows With Either Service
- Christian On The Most Common Sizing Mistake
- Frequently Asked Questions
Reading Time: 14 minutes
Should You Run 60A Or 100A To A Container Office In Ontario?
The 60A versus 100A choice for a container office comes down to the calculated electrical load. A 60-amp feed handles a small shack with a single split-system, basic lighting, a coffee maker, and maybe a microwave. A 100-amp feed gives you room for a full office layout with multi-zone climate control, a small kitchenette, computer drops, a plotter, and headroom for future load. Size it from the actual load, not from the container length.
That single decision sets the wire gauge, the conduit size, the panel cost, the trench depth if you go underground, and what the Electrical Safety Authority inspector signs off on. It also sets your ceiling. A 60A service that runs out of headroom in year three is an expensive rework, because you are not just swapping a breaker. You are pulling new conductors, re-trenching, and resubmitting to ESA.
This sizing question sits downstream of the broader connection process. If you want the wider picture first, the way the Authorization process works in Ontario is covered in our guide to wiring a container to ESA standards. This page goes deeper on the math behind the service size itself, because almost every buyer who calls us with a container office question wants this answer in concrete numbers, not abstract advice.
Here is the short version a buyer can act on. A 60A service suits a single-occupant container with one mini-split, basic lighting, and a handful of receptacles, where the calculated load stays under roughly 45 amps. A 100A service is the right call once you add dual-zone HVAC, a real kitchenette, multiple workstations, or any plan for EV charging, because those loads push past what 60A can carry safely.
Paul LeBlanc, owner, Van Blanc: “Buyers ask me which container they need, and the honest answer is that the contractor sizing the service decides that, not me. In my 19 years in the container industry I have watched too many people pick the box first and the power second. Tell us the load your electrician calculated and we will tell you which bin fits it. That order saves a re-trench down the road.”
The Standard That Governs This Decision
Service sizing for any container office in Ontario falls under CSA C22.1, the Canadian Electrical Code, Section 8 (Circuit Loading and Demand Factors). Rule 8-210 covers load calculations for non-residential occupancies, including offices. Table 14 sets a basic load of 25 watts per square metre for general lighting and receptacles in office space, with demand factors applied above that baseline. Every ESA-licensed contractor calculates against this section before they tell you 60A or 100A.
How Does CEC Section 8 Size A Container Office Service In Ontario?
CEC Section 8 sizes a container office service by calculating the connected load, applying demand factors, and rounding up to the next standard panel. Section 8 of the Canadian Electrical Code is the basis for selecting conductor sizes for services, feeders, and branch circuits, and for setting breaker ratings. For office occupancies, three rules do most of the work.
Rule 8-210 tells you how to calculate loads for offices and other non-residential spaces. Table 14 assigns a basic load of 25 W per square metre for lighting and receptacles. Rule 8-104 requires that the service ampacity at least equal the calculated load, and that continuous loads (anything running three hours or more) be sized at 125 percent of nameplate.
Demand factors matter because not every load runs flat-out at the same moment. The Canadian Electrical Code lets you apply factors so a 22 m² container office full of office equipment is not sized as if every printer, every monitor, the kettle, and the mini-split all hit peak draw on the same second.
The Three Numbers You Need Before You Call An ESA Contractor
- Floor area in square metres. A 20ft container is about 13.7 m² of usable floor. A 40ft container is roughly 27.4 m². A 40ft High Cube is the same footprint with extra headroom.
- Nameplate watts on every fixed appliance. The mini-split outdoor unit, the baseboard heaters if you use them, the water heater if you have one, the hand-dryer in the washroom. Nameplate is on a small metal sticker, usually inside the unit door.
- Continuous-vs-intermittent count. Lighting and HVAC are continuous. Coffee makers, microwaves, and printers are intermittent. The CEC treats them differently.
The Load-Calc Worksheet We Walk Through With Every Buyer
When a contractor calls us asking which service to spec, we run through a short worksheet on the phone before we even talk about which bin to send. The footprint matters because a 20ft gives you about 13.7 square metres to lay out and a 40ft roughly doubles that, and if you are still weighing the two, the trade-offs are broken down in our side-by-side look at the two most popular bin lengths. The numbers below are typical for an Ontario container office and reflect CEC Section 8 demand factors applied conservatively.
| Load Item | Typical Watts | Demand Factor | Calculated Watts |
|---|---|---|---|
| Basic lighting + receptacles (25 W/m² × 27.4 m² for 40ft) | 685 | 100% | 685 |
| Mini-split HVAC, 12,000 BTU, single zone | 1,800 | 100% (continuous) | 1,800 |
| Second mini-split or baseboard supplemental heat | 1,500 | 100% | 1,500 |
| Kettle, coffee maker, microwave (intermittent kitchenette) | 2,400 | 50% under Rule 8-210 | 1,200 |
| Computers, monitors, printers (office equipment) | 900 | 100% | 900 |
| Plotter or large-format printer (commercial) | 1,200 | 100% | 1,200 |
| Hot water tank, small point-of-use | 1,500 | 100% | 1,500 |
| Total calculated load | 10,000 | 88% effective | 8,785 W |
Convert that to amps at 240 V single-phase: 8,785 W ÷ 240 V = 36.6 A. Under Rule 8-104, the service has to be at least 100 percent of the calculated load, so 36.6 A is the floor. The next standard service size above the calculated load determines what you actually buy.
If the load lands under about 45 A, a 60A service still has reasonable headroom. If it lands between 50 and 75 A, you want 100A. Above 75 A, you are heading into 125A or 200A territory, which is rare for a single container office but real for double-stacked or paired-bin configurations.
The 25-Percent Buffer Rule Of Thumb
ESA-licensed contractors typically size at 125 percent of calculated load to leave room for growth and to keep continuous loads off the breaker’s trip threshold. On the worksheet above, 36.6 A × 1.25 = 45.7 A, which still fits inside 60A comfortably. But if the buyer mentions an EV charger or a heat pump coming in year two, that buffer evaporates and 100A becomes the honest call.
When 60A Is Honestly Enough: Three Real Container Setups
A 60A service is not undersized for every container office. For the right setup, it is correct, cheaper, and easier to permit. The three configurations below are where we see 60A working well in the field.
1. The Single-Occupant Jobsite Shack
One small mini-split, four duplex receptacles, two ceiling LED panels, a single laptop, a phone charger, and a coffee maker. Total calculated load lands around 4,500 to 5,500 watts, which is 19 to 23 amps at 240 V. A 60A service is more than enough and gives the contractor about 35 to 40 amps of headroom for occasional power tool use.
2. The Crew Lunchroom Container
Microwave, kettle, fridge, picnic-table lighting, two heating zones for January. The kitchenette appliances are intermittent and most crews are not running everything at once. Calculated load with demand factors typically sits around 30 to 40 amps. 60A handles it, with room to add a phone-bank charging strip down the road.
3. The Single-Zone HVAC Office With Two Workstations
Two computers, two monitors, a small printer, one 9,000-BTU mini-split, basic lighting, four receptacles. This is the most common small-office build we ship. Calculated load runs about 28 to 35 amps. 60A is correct, and stepping up to 100A here just spends money on copper you will not use.
Where 60A Stops Working
The moment any of the following enters the conversation, jump to 100A: a second HVAC zone for a stacked or longer container, electric baseboard heaters as a primary heat source, a hot water tank larger than point-of-use, a hand-dryer in the washroom, a commercial coffee machine drawing over 1,500 W, or any plan to add EV charging on the same service.
When 100A Is The Right Call: Full Office, Multi-HVAC, Appliances
A 100A service is the honest answer for most 40ft container office builds with two or more workstations, a kitchenette, and dual-zone climate control. The heavier the fitout, the stronger the case, and the conversions we see go furthest, like the office, cabin, and bar builds covered in our walkthrough of finished container conversions, almost always land at 100A or higher. Mobile office trailers in the industry typically run 220 V single-phase 100 A service, and the same logic applies to container offices that are essentially fixed mobile offices on a permanent footing.
Multi-Zone HVAC
A 40ft container divided into a meeting room plus open work area usually wants two mini-splits. Two 12,000-BTU outdoor units run about 3,600 W continuous, plus the air handlers inside. That alone is 15 amps of continuous draw before you turn on a single laptop. Stack that with the rest of an office load and 60A starts feeling cramped.
Kitchenette With Real Appliances
A small fridge, a microwave over the counter, a coffee maker, a kettle, a toaster oven, and a dishwasher in a fitout aimed at long-term occupancy. The kitchenette circuit alone might be calculated at 4,000 to 6,000 watts. The dishwasher is the giveaway: at that point you have a commercial-grade kitchenette and 100A becomes the right service.
Commercial Equipment Loads
A site office for a survey firm or engineering office runs a large-format plotter, multiple workstations with dual monitors, a server cabinet with a small UPS, and laser printers. The combined office-equipment load can climb past 3,000 watts continuous. Add HVAC and a kitchenette and the math points to 100A every time.
Future-Proofing Headroom
The 100A service is also the entry point for adding a future EV charger or a heat pump retrofit without redoing the service. A Level 2 EV charger at 32 A continuous (the most common size for a single-port site office unit) eats most of a 60A panel’s available capacity on its own.
Why Container Offices Sometimes Sit Between Standard Service Sizes
Standard panel sizes in Canada are 60, 100, 125, 200, and 400 amps. A calculated load of 78 amps does not have a 75A panel to live in, so the next standard size up is 100A. This is normal. The Canadian Electrical Code requires the service ampacity to at least equal the calculated load, but you cannot under-size to “split the difference.” You round up to the next standard size, and that is the panel you install.
What Wire Gauge And Conduit Size Does A Container Office Feed Need?
Wire gauge and conduit size for a container office feed are set by the service rating. Service size drives conductor selection. The numbers below assume copper conductors at 75°C insulation rating (THWN or RW90), which is the typical container-office spec.
| Service Size | Copper Conductor (Phase) | Aluminum Equivalent | Minimum Conduit (PVC, 3-wire + ground) |
|---|---|---|---|
| 60A | #6 AWG copper | #4 AWG aluminum | 1 inch |
| 100A | #3 AWG copper | #1 AWG aluminum | 1.25 inch |
| 125A | #1 AWG copper | #1/0 AWG aluminum | 1.5 inch |
| 200A | #2/0 AWG copper | #4/0 AWG aluminum | 2 inch |
For runs over about 30 metres from the main panel to the container, voltage drop becomes a factor and one or two sizes larger is typical. Rule 8-102 of the CEC limits voltage drop to 5 percent total (3 percent on the feeder, 2 percent on the branch). On long runs across a yard or back-lot, the contractor will size up rather than fight the math.
Copper costs more per foot but installs cleaner, terminates more reliably, and avoids the antioxidant-paste-and-torque-spec hassle that comes with aluminum. For a service that small, the copper premium is honestly worth it. Aluminum saves real money on 200A and bigger runs; on 60A and 100A container feeds, the savings barely register.
The Conduit Size That Surprises Buyers
Buyers often picture a small flexible cable running into the container. The reality is rigid PVC conduit, glued and supported at code-required intervals, with a sweep into the building wall. 1-inch PVC on 60A, 1.25-inch on 100A, and the bigger sizes for higher amperages. If the run is exposed to vehicle traffic or heavy equipment, EMT or galvanized rigid metal conduit replaces PVC in those sections.
How Much More Does 100A Cost Than 60A For A Container Office?
The cost gap between 60A and 100A on a container office service is smaller than most buyers expect, which is why the contractor will often nudge you toward the larger size when there is any chance of growth.
For a 25 metre underground run from an existing main panel to the container, with trench, PVC conduit, copper conductors, a sub-panel inside the container, and ESA Authorization fees, you are typically looking at:
| Cost Driver | How It Moves The Quote | Bigger On 60A or 100A? |
|---|---|---|
| Conductor gauge and metal (copper vs aluminum) | Heavier conductors for 100A cost more per metre, and copper costs more than aluminum at any size | Larger on 100A |
| Trench length and routing | Every extra metre of underground run adds conduit, wire, and excavation, and rock or paving raises it further | Roughly equal, scales with distance |
| Conduit diameter (1 inch vs 1.25 inch PVC) | The larger service needs wider conduit and slightly more labour to pull the heavier conductors | Larger on 100A |
| Sub-panel and breaker rating | A 100A panel and main breaker carry a modestly higher hardware cost than a 60A panel | Larger on 100A |
| ESA Authorization fee | The fee schedule scales modestly with service size, so the steps are the same but the fee ticks up | Slightly larger on 100A |
| Year-three rework risk | Under-sizing now means re-trenching, new conductors, and a fresh ESA submission later, which dwarfs the upfront gap | Far larger if 60A is outgrown |
The added cost of stepping up to 100A is a small fraction of the total job, driven mostly by heavier conductors, wider conduit, and a slightly higher panel and ESA fee. Compared to the cost of redoing it in year three, that incremental spend is money well placed if there is any reasonable chance you will outgrow 60A. The numbers vary by site, distance from the existing service, and how easy the trench routing is. Get a real quote from an ESA-licensed contractor before you budget.
Brantford Yard Reality
Our 4 Brantford yards ship containers across Ontario with fast 1 to 3 day delivery. Every quote comes with a real lead time, not a hopeful one. When a buyer asks us about the office build, we tell them to call their ESA-licensed contractor before they pick the container. The contractor walks the site, sizes the service, and tells you whether you are looking at a 20ft or 40ft footprint based on what fits the load. Once the spec is settled, you can see the dry and high-cube units we keep in stock for office builds on the containers we have ready for sale, and we deliver the one your contractor wires. Worth the drive for unbeatable quality, family customer service with 30 years of experience.
Future-Proofing For EV Charging And Heat Pumps
This is the section most buyers skip until it is too late. A 60A service that is correctly sized for today is undersized for an EV charger added in year two. A Level 2 charger on a 40A circuit pulls 32 amps continuous, which leaves 28 amps on a 60A panel for everything else in the office. That is not enough.
If there is any plan to add EV charging, even occasional charging of a single fleet vehicle, the answer is 100A minimum. For two ports or a higher-amperage charger, 125A or 200A is the honest call. Plan it in once, run the bigger feeder, and you never have to dig the trench twice.
Heat pump retrofits work the same way. A cold-climate heat pump rated for Ontario winters draws more than a basic mini-split, and electric resistance backup heat draws a lot more. If electrification is on the roadmap, size the service for the future load, not the current one.
The 200A Conversation
A small number of container office builds end up at 200A from the start. The triggers are: paired containers operating as one office (kitchen in one, workstations in the other), an EV charger on the same service, electric resistance heat as primary, or a build that will host trade shows or product demos with significant temporary load. 200A is not common for a single container, but it is not strange either. If your contractor recommends it, the math behind that recommendation usually holds up.
How The ESA Connection Authorization Flows With Either Service
The Electrical Safety Authority Connection Authorization process in Ontario is identical for 60A and 100A. The licensed contractor submits an Application for Inspection, the work is inspected at rough-in (before drywall, before backfill on trench), and again at final. The fee schedule scales modestly with service size but the steps are the same.
What changes by service size is the documentation. A 60A temporary feed to a short-term jobsite shack often does not. Your contractor will know the difference based on the municipality and how long the container will be on site.
For the full Authorization workflow, the steps that take you from Notification through to final Connection Authorization are laid out in sequence on our ESA process page.
Christian On The Most Common Sizing Mistake
Christian LeBlanc, second-generation operator: “The mistake I see most often is sizing for the container, not for the office that ends up inside it. Someone calls us for a 40ft bin, says it is a basic site shack, sizes the feed at 60A. Six months later they are adding a second mini-split because the south end gets hot in summer, and a year after that they want a small kitchenette. Now the contractor is back to redo the service. If there is any chance the use grows, run 100A from the start. The copper costs less than the rework.”
Christian has worked our yard since he was old enough to load a tilt-deck, and he travelled to Asia with Paul starting at 15 to walk container factory lines. He sees every kind of office build come through. The mining engineer ordering a bunkhouse, the survey firm ordering a two-workstation field office, the construction PM ordering a lunchroom for a 40-crew jobsite. The pattern is the same: the offices that get electrically resized in year two are almost always the ones that started undersized.
Every Kind Of Ontario Buyer Ends Up At The Same Family Yard
The mining engineer in Sudbury calls them intermodal containers, the Brampton GC calls them c-cans, the Norfolk farmer calls them sea cans. They all need different things from the same 8-foot-wide steel box. The contractor sizing the service is solving a different problem than the buyer choosing the bin, and that is exactly why we tell every office buyer to bring their ESA-licensed contractor into the conversation early. Paul has 19 years in the container industry and 40 years in Asian trade. Christian was raised in it. The family yard at 90 Morton Avenue East has been delivering containers across Ontario since 1995.
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Frequently Asked Questions
What is the difference between 60A and 100A service for a container office in Ontario?
60A service handles a small container with one mini-split, basic lighting, four to six outlets, and occasional appliances. 100A service supports a full office with two-zone HVAC, a kitchenette, multiple workstations, and headroom for EV or heat pump additions. Both fall under CSA C22.1 Section 8 demand factor calculations and require ESA Authorization in Ontario.
What does the Canadian Electrical Code say about office service sizing?
Rule 8-210 governs load calculations for office occupancies. Table 14 sets a basic load of 25 watts per square metre for lighting and receptacles. Rule 8-104 requires service ampacity to at least equal calculated load, with continuous loads (three hours or more) sized at 125 percent of nameplate. Demand factors apply to intermittent loads like kitchenette appliances.
What wire size do I need for a 100A container office feed?
For a 100A service using 75°C copper conductors (RW90 or THWN), you need #3 AWG copper for the phase conductors. The aluminum equivalent is #1 AWG. Minimum conduit is 1.25 inch PVC for three current-carrying conductors plus a ground. On runs longer than 30 metres, one size up is typical to keep voltage drop under 5 percent per CEC Rule 8-102.
Can I run a 60A service to a 40ft container office?
Sometimes, depending on load. A single-zone HVAC, two workstations, basic lighting, and a coffee station on a 40ft container often calculates at 28 to 38 amps, which fits inside 60A. If the build includes dual HVAC, a kitchenette with multiple appliances, or any future EV charging, jump to 100A. Have an ESA-licensed contractor run the Rule 8-210 calculation before you order materials.
How much more does 100A cost compared to 60A for a container office?
For a typical 25 metre underground feed in Ontario, 100A costs only modestly more than 60A. The gap comes from heavier conductors, slightly wider conduit, a larger sub-panel and breaker, and an ESA Authorization fee that scales modestly with service size. The total project cost is driven far more by trench length and routing than by the jump from 60A to 100A, so the upgrade premium is a small share of the job and well below the cost of re-trenching in year three. Get a real quote from an ESA-licensed contractor for your specific site.
Do I need ESA approval for a container office electrical service?
Yes. Any permanent or semi-permanent electrical service to a container office in Ontario requires Connection Authorization from the Electrical Safety Authority. The licensed contractor submits an Application for Inspection, the work is inspected at rough-in and final, and the utility connects only after Authorization is issued. Same process applies to 60A and 100A.
Can I add an EV charger later if I install a 60A service now?
Not without redoing the service. A Level 2 charger pulls 32 amps continuous on a 40A circuit, which leaves only 28 amps on a 60A panel for everything else. If there is any plan to add EV charging, even occasional, install 100A from the start. The rework cost (new conductors, new trench, new ESA submission) far exceeds the upfront upgrade.
What is the demand factor for office equipment under CEC Section 8?
Office equipment that runs continuously (computers, monitors, network gear, lighting) is calculated at 100 percent demand. Kitchenette appliances and other intermittent loads can be calculated at 50 percent under Rule 8-210 because they rarely all run simultaneously. HVAC is always 100 percent because it operates as a continuous load during heating or cooling cycles.
Do I need copper or can I use aluminum conductors for a container service?
Both are CEC-compliant. Copper is more common on 60A and 100A container services because the price difference is small at those sizes and copper terminations are simpler. Aluminum saves real money on 200A and larger services. For a small office service, the labour and reliability advantages of copper usually outweigh the modest cost.
How do I calculate the load for my specific container office?
Multiply floor area in square metres by 25 watts for basic load. Add nameplate watts for each fixed appliance (HVAC, water heater, lighting beyond basic). Apply demand factors per Rule 8-210 to intermittent loads. Total the watts, divide by 240 volts for single-phase service, and round up to the next standard panel size (60, 100, 125, or 200A). An ESA-licensed contractor runs this calculation as part of every quote.
Sources
- CSA Group. (2024). CSA C22.1:24, Canadian Electrical Code, Part I (26th Edition), Safety Standard for Electrical Installations. csagroup.org
- Electrical Industry News Week. (2024). Guide to the Canadian Electrical Code, Part I, 26th Edition, A Road Map: Section 8. electricalindustry.ca
- IAEI Magazine. (2024). Calculated Loads, Demand Loads, Demonstrated Loads, and the Application of Demand Factors in the CE Code. iaeimagazine.org
- Electrical Safety Authority. (2025). Notification, Inspection, and Connection Authorization Process. esasafe.com
- Mobile Modular Containers. (2025). How to Wire a Shipping Container: 60A-200A Panel Sizing Guide. mobilemodularcontainers.com
Reach Van Blanc in Brantford
We have been supplying shipping containers across Ontario since 1995. Our warehouse is at 90 Morton Avenue E in Brantford, and we deliver right across the province in 1 to 3 days from our 4 Brantford yards. No surprise fees, no chase-the-paperwork. Every quote comes with a real lead time, not a hopeful one.
Van Blanc Ent. Inc. 90 Morton Ave E Unit 1B, Brantford, ON N3R 7J7 +1 888-509-6658
If you are spec’ing a container office and need a hand matching the bin size to the service your contractor is sizing, give us a call. We walk through it on the phone every week.