When to upgrade your electrical service

You need a bigger electrical service when the load you plan to add, on top of the load you already have, will exceed what the service can safely carry, or when the existing service equipment is at the end of its life. The decision should rest on a load calculation or measured data, not on how old the panel looks or how often a breaker trips, because there are often cheaper ways to make room.

What "the service" means

The electrical service is everything from the utility's point of supply to the building's main disconnect: the service conductors, the meter, the main breaker or fused switch and the main switchboard or panel. Its capacity is limited by the smallest rating in that chain, and also by the utility's transformer, which the utility sizes based on what you told them when the service was first connected. A larger main breaker on its own does not make a larger service.

Signs you may need an upgrade

New load is coming

The most common trigger is a planned change that adds significant load:

• Electrification: replacing gas heating, water heating or cooking with heat pumps, electric boilers or induction
• EV charging for tenants, residents or a fleet
• A new tenant with heavier needs, such as a restaurant, lab, clinic or light manufacturing use
• An addition, or a change of use for part of the building
• New process equipment, compressors or large motors

The existing service is struggling

• The main breaker or feeder breakers trip under normal load
• Utility bills show peak demand close to the service rating
• Panels have no spare breaker spaces, and tandem breakers or sub-panels have been added over the years
• Infrared thermography finds hot connections or overloaded conductors on the service

The equipment is at the end of its life

Some older switchboards and panels are no longer supported by their manufacturers, and replacement breakers may be hard to find. Corrosion, water damage, or a history of overheating are reasons to replace equipment even if capacity is adequate. In that case, it is worth sizing the replacement for the loads you expect over the next couple of decades, since the cost difference between sizes is often small compared with doing the work twice.

Upgrade or not: working through the decision

An upgrade is the right answer when the numbers say so and the alternatives do not close the gap. The sequence below is a good way to test it.

Alternatives to a full upgrade

Before committing to new service equipment and utility work, check whether these close the gap:

• Load management. Systems that limit or shed certain loads when the building is near its peak. For chargers, see EV load management; the Canadian Electrical Code recognizes energy management systems for EV loads.
• Efficiency. An LED retrofit or better controls can free up capacity, especially in buildings where lighting is a large share of the load.
• Load shifting. Scheduling loads such as water heating or charging away from the building's peak.
• Redistribution. Moving loads between panels or phases when the problem is a single panel or an unbalanced phase rather than the service.
• Heat pump selection. Choosing equipment and backup heat strategies that limit the winter peak.

Each has limits. Load management adds controls that must be maintained, and efficiency gains are finite. If the building is likely to keep adding load, these can buy time rather than replace the upgrade.

How a service upgrade project runs

1. Load calculation. Establishes the new demand and the service size. See electrical load calculations.
2. Utility application. The utility confirms whether it can supply the new load and whether its transformer, service conductors or metering need to change. This step can take a long time, so start early.
3. Design. Drawings show the new service equipment, the route of service conductors, metering, grounding, fault current ratings and how existing feeders reconnect. Drawings for permit are sealed by a licensed professional engineer where required.
4. Permit and installation. A licensed electrical contractor obtains the permit and installs the work, with inspection by the authority having jurisdiction.
5. Cutover. The switch from old to new service usually needs a planned outage. Plan it with tenants and arrange temporary power for critical loads if needed.
6. Close-out. Updated single-line diagram, panel schedules and, where a study is needed, updated short-circuit, coordination and arc flash information.

A typical case

A small strip mall with an older service gets a lease enquiry from a restaurant. The restaurant wants a commercial kitchen with electric cooking equipment, a walk-in cooler and a larger rooftop unit. The landlord's first instinct is that the service is old and should be replaced. A better approach starts with the numbers.

Twelve months of utility bills show the building's peak demand and when it happens. The restaurant's equipment list gives the new loads, and the existing tenant space being replaced may have its own load that will come off. Adding the restaurant's demand to the measured peak, after demand factors, shows how close the total comes to the continuous rating of the service.

If the result fits with margin, the work is limited to a new feeder and panel for the tenant. If it is close, the landlord may ask the tenant to choose gas cooking, or the engineer may find that the building's service equipment has the rating needed and only the utility's transformer has to change. If it clearly does not fit, the upgrade becomes part of the lease negotiation, with the cost, the schedule and the outage planned before anyone signs.

Things that are easy to overlook

• Available fault current usually rises with a larger utility transformer, so downstream equipment ratings must be checked
• Arc flash labels will need to be updated after the change
• Electrical room space and clearances for larger equipment
• Space for the utility's transformer, pad or vault, and access for its crews
• Lead times for switchboards and transformers, which can be long
• Whether a change in voltage, such as 120/208 V to 347/600 V, would serve the building better

Voltage choice matters more than it seems. For larger buildings, see 120/208 V vs 347/600 V systems.

How ehZee can help

Our service upgrade and load calculation work begins by asking what you are trying to add and why. We assess the existing service, prepare the load calculation, look at alternatives, and where an upgrade is needed, design it and coordinate with the utility and your electrical contractor.

Common questions