Do I need a panel upgrade for solar or a battery?

EnergySage says most homeowners, especially those with newer homes, don't need an electrical panel upgrade before a solar installation. The limit is usually the panel's busbar. Under the National Electrical Code's 120% rule for connecting solar inside the panel, the main breaker plus 125% of the inverter's output can't exceed 120% of the busbar rating.

On a 200-amp panel with a 200-amp main breaker, that leaves room for a 40-amp solar breaker, or about 32 amps of continuous inverter output, roughly 7.7 kW at 240 volts. Smaller or older panels leave less room, which is why big systems on 100-amp service can trigger an upgrade.

Very. A 2023 ComEd study found roughly two-thirds of its residential customers, about 2.2 million homes, have 100-amp or smaller electrical service. Those homes are the ones most likely to hear about an upgrade, especially when adding a battery, an EV charger or a heat pump at the same time as solar.

• A supply-side connection, which ties the solar in between the meter and the main breaker, isn't limited by the 120% rule.
• A smaller main breaker, for example dropping from 200 to 175 amps, frees busbar room if your home's load allows it.
• A power control system, a listed device that limits current so the busbar isn't overloaded, can let a larger system connect without a new panel.
• A smart panel or load manager, which the 2023 electrical code lets count at its maximum setpoint in load calculations. See smart electrical panels with solar and batteries.

A ComEd study on avoiding electrical upgrades found a variety of strategies can avoid panel upsizing during home electrification projects, so ask an installer which options fit before accepting an upgrade line on a quote.

Not usually for partial backup. EnergySage says battery quotes often include a critical-loads panel that holds the circuits you want backed up, such as the refrigerator, sump pump, furnace and internet. Whole-home backup is a bigger job: in EnergySage's example, a 30 kWh whole-home system cost about three times a 10 kWh partial-backup system. See whole-home battery backup.

For ComEd, a licensed electrician files a modification and relocation service application, preferably through ComEd's New Business Portal, and ComEd assigns a project lead. Ameren Illinois asks customers to contact its Construction and Engineering team about the delivery point, meter location, scheduling and any charges, and to use an Ameren-approved meter base. In both territories you or your electrician get the local permits and inspections, and the utility may charge for some work on its side, so ask for a quote.

Illinois has no statewide electrical code; towns adopt their own. Chicago's electrical code is based on the 2017 National Electrical Code, and electrical work there must be done by a Chicago-licensed electrical contractor named on the permit.

ComEd's 2023 study put a typical service amperage upgrade at $4,000 to $6,000; a panel-only replacement is usually less. There's no federal credit for it in 2026: the IRS energy-efficient home improvement credit, which covered panel upgrades, ended for property placed in service after December 31, 2025. The ComEd and Ameren rebates are based on the size of the solar or battery system, not on panel work.

Get the upgrade priced as its own line on the quote. See what a solar quote should include.