Do I need 200-amp service?
Service size is not a one-number answer. The home’s loads, equipment, capacity, and plans need to be considered together.
Service size is a calculated number, not a slogan. The National Electrical Code's load calculation adds up what a specific house can actually demand and answers in amps, and that answer, not a sales script, is what should size your service.
What the load calculation adds up
It starts from square footage for general lighting and receptacle load, adds the fixed appliances, range, dryer, water heater, heating and cooling, then applies demand factors, because no house runs everything at full draw at once. Out comes a number to set against the service rating.
It is reproducible arithmetic: two electricians calculating the same house should reach the same result. That is what makes it worth asking for in writing.
The loads that force the question
Most 200-amp conversations are driven by electrification: an EV charger (a 48-amp charger occupies a 60-amp circuit), a heat pump replacing a gas furnace, an induction or electric range replacing gas. Stack 2 or 3 of those onto a 100-amp service and the calculation often stops fitting.
Any one of them alone frequently fits fine. That is exactly why the math comes before the assumption.
Where 100 amps stays enough
Gas heat, gas water heating, a gas range, and no vehicle charging on the horizon: houses like that usually sit comfortably inside 100 amps. An old 100-amp panel can still be a condition problem while being no capacity problem at all; that split is covered under outdated electrical panel.
Options the calculation can surface
Load-management hardware can pause or throttle an EV charger while the range or dryer runs, letting real charging live inside an existing service. Charging at 16–32 amps instead of the maximum still fills a battery overnight.
These are engineering choices, not consolation prizes, and the right one falls out of the same numbers. The EV charging load-calculation guide walks the trade-offs.
What an upgrade involves
Moving to 200 amps replaces the service conductors, the meter base, and the panel, under an electrical permit and inspection, with the utility coordinating disconnect and reconnect. The house is de-energized during the changeover, and the utility controls part of the calendar.
It is also the natural moment to bring grounding, bonding, and labeling up to date, since everything is open anyway. The work lives under panel upgrades and replacements.
Get the number first
Tell us what exists, starting with the main breaker's marking, and what you intend to add: vehicle, heat pump, range, shop, ADU. The load calculation comes first, then a recommendation you can check against it.
Request an Estimate to start, or talk it through at (206) 718-3047. If the panel is showing live distress, heat, odor, or scorching, that is a safety visit rather than a planning question, and smoke at the panel means 911. A whole-street power problem goes to the utility.
Common questions
How do I find out what service I have now?
The main breaker's handle is usually stamped with its rating, 100, 125, 150, or 200. Treat it as a starting point rather than proof; conductors and meter equipment do not always match the label, which an evaluation verifies.
Can I add an EV charger without going to 200 amps?
Often, yes. A load calculation may show room at a modest charging rate, and load-management equipment can share capacity with the range and dryer. The upgrade is the answer only when the numbers say so.
Is 200-amp service required for new houses?
No blanket rule requires it; code sizes a service by the calculated load. Builders commonly choose 200 amps for headroom, which is a planning preference rather than a mandate.
Will a bigger service change my electric bill?
No. You are billed for the energy you use, and service size is headroom, not consumption. A 200-amp house that uses the same appliances the same way pays what it paid before.