100 amps
Often found in smaller or older homes. Can work well without central air, an EV or an electric range.
Panels & capacity
100 Amp vs 200 Amp Service: Which Does Your Home Need? (Same-Day Panel Checks Explained)
"Do I need 200 amps?" is one of the most common questions we hear from homeowners in Marlboro and nearby towns, usually right before someone buys an EV, a hot tub or a heat pump. This guide shows you how to find your current service size, what uses the most power, and how electricians decide if you truly need an upgrade.
Want an answer for your own home? A licensed electrician can do a same-day panel check.
- Written by licensed electricians
- New Jersey code
- Local to Monmouth County
The short answer
Look at the main breaker in your panel to see your size. 100 amps can work for smaller homes with few big electric appliances. 200 amps is the typical size today and leaves room for central air, an EV charger and future projects. The only reliable way to know if you need more is a load calculation, not adding up breakers.
Step one
How to Find Out What Size Service You Have
It usually takes less than a minute.
Check the main breaker
Open the panel door. The large breaker at the top, or sometimes in a separate box near the meter, is usually labeled 100, 150 or 200.
Read the panel label
The sticker inside the door lists the panel's rating. The panel rating can be higher than your actual service.
Look outside
A thicker cable from the meter to the house often means a larger service, though only an electrician can confirm it.
Ask, if unsure
Older homes sometimes have mismatched parts. A quick panel check settles it.
Where the power goes
How Much Power Common Appliances Use
Big 240 volt appliances are what eat up capacity.
| Appliance | Typical circuit | Notes |
|---|---|---|
| Central air conditioner | 240V, about 15 to 40 amps | Larger homes often have two units |
| Electric range or induction cooktop | 240V, 40 to 50 amps | Induction often needs more than an old range |
| Electric dryer | 240V, 30 amps | Runs for long stretches |
| Level 2 EV charger | 240V, 40 to 60 amps | Runs for hours, usually overnight |
| Hot tub | 240V, often 40 to 50 amps | Heater runs on and off all day |
| Electric water heater | 240V, about 25 to 30 amps | Common in homes without gas |
| Kitchen counter circuits | 120V, 20 amps each | At least two required in kitchens |
Add an EV and a hot tub to a home that already has central air and an electric dryer, and a 100 amp service gets crowded fast.
The real test
Why a Load Calculation Beats Adding Up Breakers
Adding breaker numbers gives the wrong answer.
A common myth
Many people add up all the breaker numbers in their panel and panic when the total is far above 100 or 200. That's normal. Not everything runs at once, so breaker totals almost always exceed the main.
What electricians do instead
We use the method in Article 220 of the National Electrical Code, which New Jersey enforces. It accounts for your home's size, fixed appliances and how loads overlap. The result tells us if you have room, are close to the limit, or need more capacity.
What the result might tell you
- Plenty of room: add the new circuit and move on
- Close to the limit: a lower EV charger setting or a load management device may be enough
- Over the limit: it's time for a service upgrade
Planning a charger? Read about EV charger installation first, since the charger is often what tips the balance.
Side by side
100, 150 and 200 Amp Service at a Glance
Three common sizes, three different comfort levels.
150 amps
A middle step. Common in some 1970s and 1980s homes. May handle one big new load, not several.
200 amps
Today's typical size for a single-family home. Room for central air, an EV charger and future additions.
Homes with very large loads, like big estates with pools and several AC units, may need even more, such as 320 or 400 amp service.
Making the call
Signs It's Time to Move Up
If several of these sound familiar, it's worth a panel check.
- Breakers trip when two big appliances run together
- Lights dim when the AC or dryer starts
- The panel has no open spaces left
- You're adding an EV, heat pump, hot tub or addition
- Your panel is an older brand. Read whether a Federal Pacific panel is dangerous
What the upgrade involves
A service upgrade replaces the main panel and often the meter socket and service cable, with a permit and an inspection. The utility disconnects and reconnects power. It's usually done in a day or two.
See electrical panel upgrade for how we handle it.
Keep reading
More Guides From Our Electricians
Plain-English answers to the questions homeowners ask us most.
Brands & service areas
Brands and Towns We Serve
Help Across Monmouth and Middlesex County
Our licensed electricians serve Marlboro and these nearby towns.
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Questions Readers Ask
Is 100 amp service enough for a house?
It can be for a smaller home without central air, an EV or an electric range. Many modern homes with several large appliances do better with 200 amps.
Can I add an EV charger on 100 amp service?
Sometimes. A load calculation shows whether there's room. A lower charger setting or load management may make it work.
Why do my breakers add up to more than my main?
That's normal. Not everything runs at once. Electricians use a load calculation, not breaker totals.
How long does a 200 amp upgrade take?
Often one to two days, plus the permit, inspection and utility reconnect.
Do I need a permit to upgrade my service in New Jersey?
Yes. See our guide on electrical permits in New Jersey.
Not Sure If Your Panel Can Keep Up?
Book a same-day panel check and load calculation with a licensed electrician.
(732) 419-5195