Whether you need 200 A is a load-calculation question, not a guess. A typical gas-heat home under ~2,000 sq ft calculates well under 100 A and is fine on a 100 A service (the NEC minimum for a house). But adding a big electric load — a Level 2 EV charger (a 48 A unit counts as 14,400 VA), a heat pump or electric heat, an electric range + dryer + water heater, or an electric tankless heater — routinely pushes calculated demand past 100 A and forces a 200 A upgrade. Budget roughly $1,300–$3,000 for a panel-focused swap and $3,000–$6,000 for a full service upgrade. Crucially, a bigger panel is not the same as more power.
The one step that actually answers this: an NEC Article 220 load calculation. Run yours with the free electrical load calculator before you price anything — it tells you whether 100 A is enough or you need to upgrade.
⚖️ 100 A vs. 200 A at a Glance
Head to Head
| Spec | 100 A service | 200 A service |
|---|---|---|
| Main breaker | 100 A | 200 A |
| Breaker spaces | ~20 | ~40+ |
| Usable continuous (80%) | ~80 A | ~160 A |
| Service conductor (Cu) | 4 AWG | 2/0 AWG |
| Service conductor (Al) | 2 AWG | 4/0 AWG |
| Best for | Gas-appliance / modest homes | All-electric, EV, heat pump |
Conductor sizes use the NEC Table 310.12 dwelling “83% rule” — see the aluminum vs copper page.
🧮 It's a load calc, not the home's age
People assume an old house needs 200 A and a new one already has it. What actually decides it is an NEC Article 220 load calculation. It adds up your loads and applies demand factors — because you never run everything at once — so the calculated demand is far below the nameplate total. A 100 A service delivers about 80 A of usable continuous capacity; if your calc lands under that with your planned additions, 100 A is enough. If it goes over, only a service upgrade fixes it.
Run the number first. The load calculator does the Optional method (220.82) for a new/whole-house calc and the existing-dwelling method (220.83) for adding a load. A typical 2,000 sq ft gas-heat home with an electric range, dryer, and water heater calculates around 86 A — a 100 A service is fine, right up until a big new electric load is added.
🔺 You need 200 A if…
Each of these is a large discrete load, and a 100 A service has only ~80 A of headroom — so a single big addition on top of a modest existing load can tip it over:
- Level 2 EV charger — a 48 A unit counts as 14,400 VA (sized at 125%); a 40 A unit ~12,000 VA
- Heat pump or electric heat — compressor + backup strips run 10,000–15,000 VA
- Electric range (~8,000 VA) + dryer (5,000 VA) + water heater (~4,500 VA)
- Electric tankless water heater — 18,000–28,000 VA; a 200 A trigger by itself
- Hot tub (6,000–12,000 VA), pool pump, or an electric workshop
The combinations that blow past 100 A: an all-electric home adding a 48 A EV charger; or a gas home electrifying two or more of {range, water heater, heat} at once. A 2,400 sq ft home with an electric range, dryer, electric heat, and a 48 A charger calculates around 153 A — over 100 A outright.
✅ 100 A is still fine if…
Plenty of homes don't need an upgrade. 100 A is adequate when the big loads run on gas and the home is modest:
- Gas heat, gas range, gas dryer, and a gas (or gas tankless) water heater
- Modest square footage (typically ≤ 2,000 sq ft)
- Central AC but no electric heat
- No EV charger (or a lower-amp / load-managed one), no hot tub, pool, or electric shop
Remember 100 A is the NEC minimum for a one-family dwelling (230.79(C)) — you can't go lower, but the code doesn't force 200 A. Very large, fully-electrified homes with multiple EVs sometimes jump past 200 A to a 320 A (“400 A class”) or 400 A service.
🚫 A bigger panel is not more power
This is the most expensive misunderstanding. Breaker spaces and service amperage are two different things. Running out of open slots is a space problem; a service that can't pass a load calc is a capacity problem. Swapping a 100 A panel for a 200 A enclosure while it's still fed by 100 A conductors and a 100 A utility drop gives you more slots and still only 100 A of power.
Out of slots but not out of amps? A subpanel ($400–$2,000) adds breaker spaces without a full service upgrade — the cheaper right answer when the load calc shows spare capacity. Only when the calculated demand exceeds the service rating do you actually need to upgrade the service.
💰 What an upgrade costs
The published ranges look contradictory until you separate the scope. A panel-focused swap — replacing the box where the existing service entrance is adequate — runs about $1,300–$3,000. A full service upgrade — new panel, meter base, service mast/conductors, and utility coordination — runs about $3,000–$6,000. The spread is driven by overhead vs underground service, mast height, whether the panel must be relocated, aluminum vs copper feeders, permit and utility fees, and regional labor (which is half or more of the total).
Budget for code catch-up that gets triggered when service equipment is replaced: a whole-home surge protector is now required (NEC 230.67; ~$200–$800 installed), and inspectors commonly require AFCI/GFCI breaker updates and grounding-electrode upgrades on older panels. A hazardous panel (Federal Pacific, Zinsco) is its own reason to upgrade regardless of amperage.
This is utility + permit + licensed-electrician work. The line-side lugs stay live even with the main off, only the utility may pull the meter, and they won't reconnect without permitted, inspected work by a licensed electrician. DIY here is illegal and can void your insurance. A federal tax credit (30%, up to $600) may apply to a qualifying upgrade — confirm current eligibility.
Prices last reviewed August 2026. Upgrade costs vary widely by scope (a panel swap vs a full service upgrade with new utility-side equipment) and by region — published ranges conflict for exactly that reason. Treat these as planning ranges, not quotes; get three itemized, licensed bids.
🧭 The bottom line
Don't upgrade on a hunch. Run a load calculation: if your demand with planned additions stays comfortably under ~80 A, keep your 100 A service. If you're only out of breaker slots, add a subpanel. If the calc exceeds your service rating — usually because of an EV charger, a heat pump, or going all-electric — upgrade to 200 A (and price a 320/400 A service if you approach ~160 A). For EV charging specifically, ask about a load-management device before defaulting to a full upgrade.
Adopted NEC editions and utility rules vary and change what's required — confirm with your AHJ and get itemized, licensed quotes that spell out scope and any code catch-up. Start with the load calculator, and size any new service conductors with the wire size calculator.
Estimate your Electrical Load materials
What size electrical service do you need? Free NEC Article 220 load calculator — Standard or Optional method, minimum service amps and wire size.
Estimate with the Electrical Load Calculator →