Electrical Panels & Service Upgrades
100-Amp vs 200-Amp Service: Which Does Your Home Need?
100-amp service powered most mid-century homes comfortably. Electrification — heat pumps, induction ranges, EVs — is what pushes homes toward 200 amps. Whether you actually need the upgrade comes down to a load calculation, not a guess.
Updated 2026-10-15
When 100 amps is enough
A modest home with gas heat, gas water heating, and a gas range can live comfortably on 100A service even with central air. Adding a Level 2 EV charger on top of that is often possible with a smaller charger setting or load management.
When 200 amps makes sense
The common triggers:
- Switching from gas to an electric heat pump, water heater, or range
- Adding a Level 2 EV charger at full output, or two EVs
- Additions, ADUs, finished basements, or a hot tub
- Larger homes with electric heat or multiple HVAC systems
- Future-proofing during a remodel when walls are already open
How the load calculation works
Electricians use NEC Article 220. For existing homes, 220.87 allows using the highest demand from 12 months of utility data plus 125% of the new load. The optional dwelling method (220.82) totals general lighting, appliances, and HVAC with demand factors. If the result fits within 100A, you may not need an upgrade at all.
Some utilities share smart-meter interval data on request — it's the most accurate input you can give your electrician.
Beyond 200 amps
Large all-electric homes, homes with multiple EVs, or homes with big shops sometimes go to 320/400A service. That usually requires a different meter base and utility coordination, so ask your utility about lead times early.
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Frequently asked questions
Does 200-amp service raise my electric bill?
No. You pay for energy used, not service capacity. A larger service just allows more simultaneous load.
How much more does 200A cost than replacing a 100A panel?
Replacing a 100A panel like-for-like is generally less expensive than a full service upgrade, which adds meter base, service conductors, grounding, and utility coordination — often a difference of several thousand dollars depending on your service type.
Do I need the utility involved?
For a service upgrade, yes. The utility disconnects and reconnects the service and may need to upgrade the drop or transformer. Some charge fees; others cover the drop.
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This guide is general information, not engineering or legal advice. Electrical codes are adopted and amended locally — consult a licensed electrician and your local building department for your project.