Comparison
100 amp vs 200 amp electrical panel
There is a reflex in this trade to recommend 200 amps for every house, and it is usually right but not always. Upgrading a service you do not need is a few thousand dollars spent on nothing, and it happens often enough to be worth checking before you sign.
The deciding factor is not square footage and it is not the age of the house. It is how many large continuous loads the home carries, and whether that number is about to change.
100 amp service
Adequate for gas-heated homes with modest load
Already installed
200 amp service
Required once you add large continuous loads
$2,200 – $4,800
| Factor | 100 amp service | 200 amp service |
|---|---|---|
| Typical breaker spaces | 16–24 | 32–42 |
| Gas heat, gas water, gas cooking, no EV | Generally adequate | Unnecessary today |
| Central air conditioning | Usually fine | Comfortable |
| EV charger at 40–48 amps | Needs load management or upgrade | Absorbs it easily |
| Electric heat or a heat pump | Not viable | Required |
| Hot tub or pool equipment | Rarely enough | Standard |
| Induction range conversion | Tight | Fine |
| Insurer and inspector attitude | Fine if modern breaker equipment | Fine |
| Cost to install today | Nothing — you have it | $2,200 – $4,800 |
| Cost if you upgrade twice | Full price again later | Paid once |
The verdict
Which one you should actually choose
Stay on 100 amps if…
Your heat, water heater, dryer and cooking are all gas, you have no EV and no plans for one, and your panel is modern breaker equipment with free spaces. A load calculation under NEC Article 220 will almost certainly confirm you are fine, and that calculation costs far less than an unnecessary upgrade.
Upgrade to 200 amps if…
You are adding an EV charger, a heat pump, electric heat, a hot tub, or converting a kitchen to induction. Any one of those is a large continuous load, and adding it to a 100-amp service either fails the load calculation outright or leaves you with no headroom for the next thing.
You may only need a sub-panel if…
Your 200-amp service is healthy but the panel has no free breaker spaces. That is a physical problem, not an electrical one, and a sub-panel at $900 to $2,000 solves it for a fraction of a service upgrade. Make sure whoever quotes you has distinguished between the two — plenty of quotes do not.
Upgrade regardless if…
You have a fuse box, or a Federal Pacific Stab-Lok or Zinsco panel. That is not a capacity question, it is an equipment question, and several insurers writing in Illinois surcharge or decline policies on homes that still have them.