Quick answer
These solve different shortages. A subpanel adds breaker spaces — more circuits fed from the capacity you already have, at $1,500–$3,500. A service upgrade adds amps — a bigger pipe from the utility, at $8,000–$16,000 for 100A→200A. The NEC load calculation tells you which shortage is real: full panel with headroom to spare wants a subpanel; loaded-up service wants the upgrade, and no subpanel can substitute.
- Spaces vs amps is the whole decision: a subpanel multiplies breaker slots; only a service upgrade multiplies capacity.
- The NEC Article 220 load calculation is the arbiter — it's arithmetic, not opinion, and it's how we (and inspectors) size everything.
- The canon prices tell the story: subpanel $1,500–$3,500, service upgrade $8,000–$16,000 — a subpanel bought when you needed amps is money spent to still trip the main.
- Detached shops, ADUs, and remote additions want subpanels regardless — one feeder out, local breakers there, code-required disconnects satisfied.
- Electrification stacking (heat pump + EV + induction) is what pushes real homes from 'spaces problem' to 'amps problem' — plan the sequence once.
At a glance
| Service/panel upgrade | Subpanel | |
|---|---|---|
| What it adds | Amps — total service capacity | Spaces — more circuits from existing capacity |
| Typical trigger | Load calc near/over service rating | Full panel, healthy load calc |
| Canon cost | $8,000–$16,000 (100A→200A) | $1,500–$3,500 |
| Utility involvement | Yes — service coordination | None |
| Where it shines | Electrification headroom for decades | Shops, ADUs, additions, crowded panels |
| Rebate path | WA HEAR panel allowance (income-eligible, electrification-enabling) | HEAR wiring allowance may apply |
What does each option cost installed in the Seattle area?
These ranges are our published, client-confirmed panel canon. The expensive mistake in this category isn't picking the pricier option — it's buying the cheap one twice because the load calculation never got run.
| Option | Typical installed range | What that covers |
|---|---|---|
| Add a subpanel | $1,500–$3,500 | Feeder breaker, feeder run, subpanel with new spaces — sized and placed for the circuits it will host. |
| Service upgrade (100A → 200A) | $8,000–$16,000 | New service equipment, meter/mast work as needed, utility coordination, permit, inspection. |
| Panel replacement (same size) | $4,000–$9,000 | When the box itself is the problem (age, recalled brands, damage) but capacity is adequate. |
What changes the price
- The load calculation: NEC 220 arithmetic on your actual square footage and appliances — run it before deciding anything.
- Feeder distance on subpanels: a garage 80 feet away costs more feeder than a subpanel beside the main.
- Utility scope on upgrades: overhead vs underground service and meter location swing the range.
- Coming loads: an EV charger or heat pump on next year's list belongs in this year's calculation.
- WA HEAR: up to $4,000 toward panel work and $2,500 toward wiring for income-eligible households when the work enables electrification.
Ranges are representative Seattle / Puget Sound installed prices, not a quote — your home's specifics set the real number. Eco gives you an upfront price before any work begins.
How do they work differently?
What a subpanel actually does
A feeder breaker in your main panel sends power through a heavy cable to a second, smaller panel — nearby or across the property — whose breakers serve new circuits. It reorganizes and extends distribution, which is why it's perfect for a detached garage, an ADU, or a main panel with zero open slots. What it cannot do is create a single new ampere: everything it serves still flows through your existing service and its main breaker.
What a service upgrade actually does
It replaces the bottleneck itself: new service conductors coordinated with the utility, a new meter base where needed, and a new 200A main panel. The whole home's ceiling rises — every future circuit, charger, and compressor draws from real headroom. It's the bigger project because it touches the utility interface, and it's the only fix when the load calculation says the service, not the panel face, is what's full.
Pros and cons, honestly
Service/panel upgrade
Pros
- Solves the amps problem — the only thing that does
- Decades of headroom for electrification stacking
- Often modernizes grounding, bonding, and protection in the same project
- HEAR panel allowance can apply for income-eligible electrification projects
Cons
- The expensive option ($8,000–$16,000)
- Utility coordination and a planned outage day
- Overkill if your only problem is breaker spaces
Subpanel
Pros
- Solves the spaces problem at a fraction of the cost ($1,500–$3,500)
- Puts breakers where the loads are — shop, ADU, addition
- No utility involvement; fast to permit and install
- Cleans up crowded, tandem-breaker-riddled main panels
Cons
- Adds zero capacity — the main breaker is still the ceiling
- A wasted purchase if the real shortage is amps
- Feeder runs to distant buildings carry real cost
Which one should you choose?
Choose the service upgrade when
The load calculation says so — an EV charger, heat pump, induction range, or ADU pushes your computed load against a 100A (or even 125A) service. Also when the existing service equipment is itself end-of-life, or when you're electrifying on a schedule and want the capacity question answered once, with HEAR support where eligibility applies. No number of subpanels substitutes here.
Choose the subpanel when
The load calculation shows real headroom but the panel face is full — every slot used, tandems already squeezed in — or the new circuits live somewhere else entirely: the detached shop, the DADU, the basement build-out. You get organized distribution and local disconnects for a fraction of upgrade money, and the main service keeps doing its adequate job.
Also consider: load management
Between the two sits a third path: smart load management. SPAN-class smart panels and simpler devices (like an EV circuit splitter) pace flexible loads so total demand stays inside your existing service — NEC provisions recognize managed loads in the calculation. When one big flexible load is the driver, management can defer the utility-side upgrade entirely; our SPAN vs traditional panel comparison covers the tradeoff.
The verdict, by situation
Service upgrade
Buy amps when amps are short
The load calc is the tell. If computed demand crowds the service rating, this is the fix — everything else is postponement.
Subpanel
Buy spaces when spaces are short
Full panel, healthy load calc: the subpanel is the proportionate, fast, and dramatically cheaper answer.
Load management
The clever middle
When one flexible load (usually the EV) is what breaks the calc, managed charging or a smart panel can keep you inside the service you own.
Which Washington homes this fits
100A home adding an EV charger and heat pump, Shoreline
Run the calc first — this stack usually lands in service-upgrade territory, with HEAR allowances if income-eligible. Sequence panel before equipment.
200A home with a full panel face, new hot tub circuit needed
Subpanel: the amps exist, the slots don't. An afternoon of feeder work beats five figures of unnecessary service work.
Detached garage becoming a woodshop, Everett
Subpanel in the garage regardless of anything else — local breakers, local disconnect, one feeder out.
DADU project, Seattle
Usually both questions at once: the DADU wants its own subpanel, and the combined load calc decides whether the main service grows too.
Ready to compare for your home?
Get honest numbers for both options side by side — an upfront range, the considerations, and the rebates you qualify for, before any work begins.
Continue exploring
- BookElectrical panel upgrades
- BookPanel upgrade services
- BookEV charger installation
- Compare200-Amp vs 100-Amp Service: How Much Panel Does Your Home Actually Need?
- CompareFuse Box vs Breaker Panel: Is the Old Fuse Box Actually Unsafe?
- ComparePanel Repair vs Replacement: Which Does Your Breaker Box Actually Need?
- GuidePanel upgrade decision guide
- GuideSPAN smart panel vs traditional panel
- GuideElectrical load calculator (NEC 220)
- GuideElectrical panel cost guide
- CompareAll electrical comparisons
Common questions
How do I know if I need amps or just spaces?
Run the NEC Article 220 load calculation — it's arithmetic on your square footage and fixed appliances, and it's exactly what we and the inspector use. Our free online load calculator walks the same math. Full panel face plus comfortable calculated load = subpanel; calculated load crowding the service rating = upgrade.
Can a subpanel let me add an EV charger?
Only if the service has the amps to spare — the subpanel just provides the breaker slot. A 48A charger on a 100A service usually fails the calculation no matter where the breaker sits. That's when the real choices are a service upgrade or load management (a paced charger or smart panel) that keeps demand inside the service.
Does a subpanel need its own ground rod?
In a detached building, yes — subpanels there get their own grounding electrode system, plus the required separation of neutrals and grounds that inspectors check closely. It's routine work for us, and precisely the kind of detail that makes permitted subpanel installs worth their price.
Which one helps my home's resale more?
The one your house actually needed. A 200A service reads as 'EV-ready, heat-pump-ready' to buyers and appraisers; a tidy subpanel-fed shop or ADU reads as finished, permitted work. What hurts is the improvisation buyers' inspectors flag: tandem breakers stacked into a crowded panel doing a subpanel's job.
Last updated: 2026-07-17
Sources & references
Equipment ratings, program details, and industry figures on this page come from manufacturers and primary sources, linked below. Verify program status and requirements for your home where applicable.
Code & permits
- Panel, subpanel, and service work in Washington requires electrical permits and inspection — WA L&I — Electrical permits, fees & inspections
Rebates
- WA HEAR provides allowances toward panel (up to $4,000) and wiring (up to $2,500) work for income-eligible electrification projects — WA Commerce — HEAR program