The large majority of Connecticut homeowners asking about a panel upgrade are upgrading from 100A service — either because a contractor told them they need more capacity, they’re adding an EV charger, or the panel is aging out. In most of those cases, 200A is the right answer. A smaller number genuinely need 400A. And occasionally the right answer is neither — a sub-panel is the more cost-effective path.
Here’s how to think through which option makes sense for your home.
The Starting Point: Most CT Homes Are Still on 100A
Connecticut’s older housing stock — and there’s a lot of it — was commonly built with 100A service. In 1960 or 1970, that was considered adequate for a single-family home. Today, 100A service is the bottleneck for any homeowner who wants to add an EV charger, run central AC alongside electric appliances, install a heat pump, or prepare for any significant load additions.
100A service at 240V can carry roughly 24,000 watts total — but the safe continuous load is 80% of that, or about 19,200 watts. A central air conditioner might draw 3,500–5,000 watts. A dryer 4,000–6,000 watts. An EV charger on a 50A circuit draws up to 9,600 watts. You can see how 100A fills up quickly with modern appliances.
Upgrading to 200A — 200A at 240V, or about 48,000 watts total capacity — more than doubles your available headroom.
When 200A Service Is the Right Upgrade
For the overwhelming majority of Connecticut single-family homes, 200A service is sufficient — both now and for the foreseeable future. Specifically, 200A makes sense if:
- Your home is under 3,000–3,500 square feet with standard HVAC
- You have or plan to have one or two EVs (even two 40A EV chargers fit comfortably in a 200A service with thoughtful load management)
- You don’t have unusual high-draw equipment: no heated pool, no large workshop, no commercial-grade equipment
- You’re not planning a major addition that would substantially change the home’s load profile
A 200A service with a properly sized panel — typically 40 or 42 circuits — gives you room to add circuits as your needs grow. For most Connecticut homeowners, this is the upgrade they need and the upgrade they should do.
When 400A Service Makes Sense
400A service is genuinely warranted in a minority of residential situations. The cases that actually justify the cost:
Large homes with high load profiles — Homes over 4,000 square feet with whole-home electric HVAC, electric ranges, and other high-draw appliances may legitimately load a 200A service near capacity, especially as EV chargers are added.
Multiple EV chargers — Two or three EV chargers in a household with high HVAC and appliance loads can push a 200A service. One or two chargers with a load management device often stays within 200A; a household with three or four EVs and heavy coincident loads is a legitimate 400A candidate.
Whole-home generators — Some large standby generator setups benefit from 400A service, particularly when the generator panel needs to parallel the service panel.
Heated pools or hot tubs — A large heated pool adds 5,000–10,000+ watts of continuous load. Combined with other large loads, that can genuinely push a home toward 400A.
Home additions significantly expanding the home — If you’re adding 1,500+ square feet with its own HVAC zone and significant electrical loads, the math on 200A may no longer work.
Home offices with heavy equipment — Specific to homeowners running servers, video production setups, or high-draw professional equipment at scale.
What 400A Service Actually Is
“400A service” is a bit of a shorthand. In practice, 400A residential service is delivered as two 200A services — either:
Two separate 200A panels — One main service panel and one secondary panel, each fed by their own 200A service conductors from a 400A meter base. This is the most common configuration.
A single 400A main panel — Less common but available. These are large, expensive panels; many electricians prefer the dual-200A approach because it’s more flexible for load management.
Either way, you’re paying for two 200A services’ worth of utility infrastructure, a larger meter base, larger service entrance conductors, and the associated permit and utility work. That’s where the cost increase comes from.
The Cost Difference
200A panel upgrade in Connecticut: $1,800–$2,800 This is the standard residential upgrade — new 200A panel, breakers, permit, inspection, utility coordination. Most Connecticut homes in good structural condition fall in this range.
200A full service upgrade (including service entrance): $2,200–$3,800 When the meter base, service entrance conductors, or weatherhead mast also need replacement, you’re doing a full service upgrade. Common in homes built before 1975.
400A service upgrade in Connecticut: $4,000–$5,500+ 400A involves a new 400A meter base, heavier service entrance conductors, two panels or a large single panel, and additional utility coordination. Budget at the higher end if the service entrance run is long or if other work is needed simultaneously.
The cost difference between a 200A upgrade and a 400A upgrade is real — typically $2,000–$3,000 more for 400A. That’s worth paying if you have the load to justify it. It’s not worth paying as general future-proofing if you don’t have a specific reason.
The Future-Proofing Question
We hear it regularly: “Should I just go to 400A now, in case I need it someday?”
Our honest answer: usually no — unless you have a specific reason to expect that load growth. Here’s why:
You can add capacity later. If your load requirements grow in five years — you add a third EV, you build an addition — upgrading from 200A to 400A then is a defined cost at a defined time. You’re not locked in.
The premium is real money now. The extra $2,000–$3,000 for 400A over 200A is money you’re spending today for capacity you may never need.
Sub-panel as an alternative. If the specific need is more circuits rather than more total amperage, a sub-panel often solves the problem at lower cost.
The exception: if you’re building a new addition, finishing a basement with a significant load, adding a heated pool, and adding multiple EVs all within the next two years, the calculation changes. Doing it all at once when the utility coordination is already scheduled is more cost-effective than doing it in two separate service upgrades.
The Sub-Panel Option
Before committing to 400A, consider whether a sub-panel solves the actual problem:
If your main panel has adequate amperage (200A) but is out of physical breaker space — you want to add an EV charger, a hot tub, and a workshop circuit but there are no open slots — a sub-panel fed from the existing 200A main panel gives you more circuits without upgrading the utility service.
Sub-panels typically cost $600–$1,500 depending on location and amperage, which is substantially less than the difference between a 200A and 400A service upgrade. If the issue is circuit space rather than total amperage, start with this conversation.
What Drives the Cost
Regardless of whether you’re doing 200A or 400A, the cost variables are similar:
- Panel brand — We favor Square D QO for its quality and parts availability; Siemens is also solid. Off-brand panels save money upfront and cost more in the long run.
- Service entrance condition — If the meter base and conductors need replacement, cost goes up regardless of amperage
- Mast condition — A rusted or undersized weatherhead mast adds $300–$500
- Utility coordination — All three CT utilities (UI, Eversource, Wallingford Electric) require disconnect/reconnect; scheduling varies
- Permit and inspection — Required for all panel work in Connecticut; included in our quotes