A commercial building has outgrown its electrical service when the load it actually carries approaches the capacity the service was sized for, usually somewhere past 80 percent of rating, and adding the next piece of equipment would push it over. At that point a breaker swap or a new circuit will not help. You need a panel upgrade, a sub-panel, or a full service upgrade, and which one you need depends on where the bottleneck sits.

This guide covers how to tell the difference, what the work involves in Lynnwood, Seattle, and the surrounding King and Snohomish County cities, and how permitting and utility coordination change depending on which side of the county line your building sits on.

What “outgrown its service” actually means

Most commercial buildings in the Puget Sound region were served at 200, 400, or 800 amps based on the loads that existed when they were built. Those loads have changed. Over the past decade the same square footage now has to carry:

• Heat pumps and electric rooftop units replacing gas heat
• Level 2 electric vehicle chargers at 30 to 50 amps each
• Denser server, network, and point-of-sale equipment
• LED retrofits that lowered lighting load but freed up capacity that new equipment immediately consumed
• Tenant improvements that added kitchens, shops, labs, or production equipment

The National Electrical Code requires continuous loads to be limited to 80 percent of the overcurrent device rating. In practical terms, a 400 amp service running 320 amps continuously is finished. It may never trip a breaker, and it is still out of room.

Service, panel, or sub-panel: three different problems

Symptom	Likely bottleneck	Typical fix
Panel is physically full, service has spare capacity	Circuit slots	Add a sub-panel
Panel is old, undersized, or a known problem brand, service capacity is adequate	Distribution equipment	Replace the panel and feeders
Measured demand is near 80 percent of the service rating	Incoming service	Service upgrade, for example 400A to 800A
One area of the building browns out under load, rest is fine	Feeder length or sizing	New feeder and remote panel

Getting this wrong is expensive in both directions. Replacing a service when you only needed circuit slots wastes money and downtime. Adding a sub-panel to a service that is already maxed out just moves the overload downstream.

How a load analysis settles the question

Do not size an upgrade from the nameplate ratings on your equipment. Nameplate totals almost always overstate real demand, and sizing from them leads to buying more service than the building will ever use.

A proper assessment has four parts:

1. Recorded demand data. A logger is placed on the service for a representative period, typically a week or longer, to capture actual peak demand instead of theoretical load.
2. A code load calculation. The recorded data is reconciled against an NEC Article 220 calculation, including the demand factors and continuous-load rules that apply to your occupancy.
3. Planned additions. Any equipment you intend to add in the next three to five years gets added to the calculation, because the cost difference between sizing once and sizing twice is enormous.
4. A condition assessment. Thermal imaging on the existing gear, breaker condition, bus bar condition, grounding and bonding, and labeling. Heat that shows up on an infrared scan sometimes reveals a loose connection that was masquerading as a capacity problem all along.

If you are still deciding whether an evaluation is warranted, our article on the seven signs a commercial panel needs an upgrade covers what to look for before you call anyone.

Where the work differs between Lynnwood and Seattle

The engineering is the same on both sides of the King and Snohomish County line. The approvals are not, and that is what drives schedule.

Utility coordination

Any upgrade that changes the incoming service involves the serving utility, because they own the transformer, the service conductors, and the meter. In our service area that generally means:

• Seattle: Seattle City Light
• Lynnwood, Edmonds, Mountlake Terrace, Everett, Mill Creek, Mukilteo, Bothell: Snohomish County PUD
• Bellevue, Kirkland, Redmond, Renton, and much of King County outside Seattle: Puget Sound Energy

Each has its own application process, its own engineering review queue, and its own lead time for transformer work. On larger service upgrades, utility engineering is frequently the longest item on the schedule, longer than the electrical work itself. Start that application early.

Permits and inspection

Electrical permits and inspections in Washington are issued either by a city or county that runs its own electrical program, or by the Washington State Department of Labor and Industries where the local jurisdiction does not. Seattle runs its own program through the Seattle Department of Construction and Inspections. Several Snohomish County jurisdictions fall under L&I. Because programs change and scope matters, the permitting authority should be confirmed for your specific address before the schedule is set, not after.

Whoever holds the permit, expect the same core requirements: a licensed electrical contractor pulling the permit, plans or a load calculation for anything that changes service capacity, and an inspection before the utility will energize.

Seismic, clearance, and location

Older Puget Sound buildings frequently fail on things that have nothing to do with capacity. Working clearance in front of gear under NEC Article 110.26 is the most common one, followed by gear mounted in spaces that no longer qualify, and seismic bracing on larger equipment. If the new gear is physically larger than what it replaces, verify the clearances before the equipment is ordered.

What the project actually looks like

For a typical commercial panel or service upgrade, the sequence runs:

1. Assessment and load analysis — on-site evaluation, logging, and a written recommendation.
2. Design and permitting — one-line diagram, load calculation, equipment submittals, permit application, and the utility application in parallel.
3. Equipment procurement — switchgear and larger panelboards have carried long lead times since 2021. This is often the second longest item on the schedule.
4. Shutdown planning — the shutdown window is negotiated with you, building management, and any affected tenants. Most commercial upgrades are cut over on a weekend or overnight.
5. Cutover and testing — demolition of old gear, new panel and feeder installation, terminations, torque verification, and circuit testing.
6. Inspection, energization, and documentation — inspection sign-off, utility energization, panel schedules, as-builts, and test results.

Planning the downtime

The shutdown is usually the part that worries building owners most, and it is the most controllable part of the project. A few things that keep it short:

• Schedule the cutover outside operating hours, which most commercial upgrades allow.
• Identify loads that cannot go dark, such as freezers, servers, life safety, and elevator recall, and plan temporary power for them specifically.
• Have all terminations pre-built and all gear on site before the window opens.
• Confirm inspector availability before committing to the window, because an unfinished inspection is what turns a one-night shutdown into two.

A well-planned commercial cutover is typically measured in hours, not days. What extends it is discovery: unlabeled circuits, undocumented modifications from past tenants, and conduit that does not go where the drawings claim. That is an argument for the condition assessment before, not during, the shutdown.

What drives cost

There is no useful flat price for a commercial upgrade, but the variables are predictable:

• Amperage and equipment class. The jump from panelboard to switchgear is a step change in cost.
• Whether the service itself changes. Utility-side work, new transformer, new service conductors, and metering add both cost and calendar time.
• Distance and routing. Feeder length, trenching, and core drilling.
• Existing conditions. Asbestos-era materials, clearance corrections, grounding upgrades, and seismic bracing.
• Schedule. After-hours and weekend labor costs more, and is almost always the right call anyway.

The comparison worth running is not upgrade versus no upgrade. It is a planned upgrade on your schedule versus an emergency replacement after a failure, with the tenant disruption and expedited equipment pricing that comes with it.

Frequently asked questions

How do I know whether I need a sub-panel or a full service upgrade? A load analysis answers it. If measured demand is comfortably under 80 percent of the service rating and you simply have no open slots, a sub-panel is the right fix. If demand is at or near 80 percent of the service rating, adding a sub-panel solves nothing and you need a service upgrade.

How long does a commercial panel upgrade take in the Seattle area? Field work is often a single weekend. The full project timeline is driven by utility engineering, permitting, and equipment lead times, which are typically measured in weeks to months. Start the utility application as early as possible.

Will my building have to close? Rarely. Most commercial upgrades are cut over after hours or on a weekend, with temporary power for loads that cannot be interrupted.

Do I need a permit to upgrade a commercial panel? Yes. Commercial panel and service work requires a permit and inspection, issued either by the local jurisdiction or by Washington State Labor and Industries depending on the address. Your electrical contractor should pull the permit and coordinate the inspection.

Can I upgrade now for EV chargers later? Yes, and it is usually cheaper to do it in one pass. Each Level 2 charger draws roughly 30 to 50 amps, so charger plans should be included in the load calculation up front rather than triggering a second upgrade a year later.

Planning an upgrade in King or Snohomish County

Electrical Support Company has provided commercial and industrial electrical service across Western Washington since 2015. Our electricians are union signatory and IBEW-trained, and every upgrade is scoped, executed, and documented to NEC and NFPA standards, with panel labeling, test results, and inspection-ready records delivered at closeout.

We perform load analyses for commercial buildings across Snohomish County and King County, dispatched from our Lynnwood headquarters. See what an upgrade involves on our commercial panel and service upgrades page, or review the panel upgrade FAQ.

To schedule an assessment, call (425) 583-4869 or request a quote. We respond within one business day.