Skip to content
ElectraKit
Open menu

Service Upgrade from 100 to 200 Amps

A crowded 100 A panel is a symptom, not a diagnosis. Decide the upgrade with a load calculation, then size service conductors, grounding and the permit package against the utility and AHJ — in that order.
Code basis
220.82 / 220.83, 230.79(C)
Trigger
Calculated load vs service
Typical target
200 A residential
Do first
Load calculation

The Procedure

5 steps, in the order the code applies them.

  1. Step 1

    Run the dwelling load calculation

    Use optional or existing-dwelling methods as appropriate. Include the loads that caused the upgrade conversation — EVSE, HVAC, shop subpanel.

  2. Step 2

    Compare with the installed service rating

    If the calculated load exceeds the existing service, a larger service is on the table. If it does not, look at panel replacement or rearrangement instead.

  3. Step 3

    Size service conductors and equipment

    Select conductors, meter fittings and service equipment for the new rating, including temperature and product constraints.

  4. Step 4

    Coordinate grounding and bonding

    Service upgrades reopen grounding electrode and bonding decisions. Do not carry forward an undocumented existing arrangement without checking it.

  5. Step 5

    Build the permit and utility package

    Submit the load calculation, one-line or riser information the AHJ wants, and any utility application required for the new service size.

Do the load calculation first

A full panel is not proof that the service is overloaded, and empty spaces are not proof that it has capacity.

The load calculation decides whether the existing service rating has headroom after the proposed loads are added.

The upgrade is a workflow

After the load result, size service conductors, grounding and the permit package against the adopted edition and utility requirements.

Local service equipment rules and utility standards can add requirements beyond the site calculators.

Decision Guide

The choices that change the answer, and how to make them.

  • Full breakers are not proof of overload

    A panel can be physically full and still within calculated load, or half empty and already overloaded on paper.

  • Utility rules can exceed NEC minimums

    POCO conductor, socket and enclosure standards may require a specific assembly. Confirm before ordering.

  • 200 A is common, not automatic

    Some dwellings need more than 200 A after electrification; others can stay at 100 A with load management. Let the calculation decide.

FAQs

When does a house need a 200 amp service?
When the dwelling load calculation, after planned additions, exceeds what the existing service rating can carry — often after EV charging, electric range/heat, or large shop loads are added to a 100 A service.
Is a full 100 amp panel enough reason to upgrade?
No. Space and load are different problems. Run the load calculation before committing to a service upgrade.
What documents do I need for a service upgrade permit?
Typically a load calculation with line items, a clear service size request, and whatever one-line or site information the AHJ and utility require.

Calculated against the NEC 2023 edition using 220.82, 220.83, 230.79(C). Confirm the edition adopted by your AHJ, which may differ and may carry local amendments.

Not covered by this tool

  • Motor, air-conditioning and welder circuits, which are sized under their own articles.
  • Conductors in free air and photovoltaic circuits.
  • Parallel conductor sets, taps and busbars.
  • Local amendments, which can be stricter than the published code.

Data last verified