Naperville renewable energy interconnection: tiers, fees and insurance

How the size is measured

the capacity of the facility to deliver alternating current energy as reflected on the approved building permit. Naperville is the only jurisdiction in the platform that defines the governing number by reference to the permit rather than to a datasheet, which has a practical consequence: if the permit set lists the DC array size, that becomes the nameplate rating of record, including for the 50 kW insurance step.

Size bands and what each one obliges

50 kW or less Size 0 to 50 kW	Liability coverage of not less than $300,000 per occurrence is required, from a carrier licensed in Illinois with an A.M. Best rating of not less than A IX, primary over the city’s own coverage and with subrogation waived. Residential permit fees are $132 including two inspections, with $50 for each additional inspection. $300,000 per occurrence liability coverage, primary, subrogation waived, A.M. Best A IX carrier Proof of insurance before interconnection Dedicated disconnect switch mounted separately from the meter socket, labeled Generator Disconnect Switch
Over 50 kW to 1 MW AC Size 50.001 to 1000 kW	Coverage rises to not less than $1,000,000 per occurrence and the City of Naperville must be named as an additional insured. A homeowner policy will often not deliver additional insured status from an A IX carrier, so this needs to be priced rather than assumed. Commercial permit fees run about $203 for a simple installation. $1,000,000 per occurrence liability coverage with the City of Naperville named as additional insured A.M. Best A IX carrier, primary coverage, subrogation waived Notice to the utility within 24 hours of any cancellation or material modification

50 kW or less Size 0 to 50 kW

Liability coverage of not less than $300,000 per occurrence is required, from a carrier licensed in Illinois with an A.M. Best rating of not less than A IX, primary over the city’s own coverage and with subrogation waived. Residential permit fees are $132 including two inspections, with $50 for each additional inspection.

$300,000 per occurrence liability coverage, primary, subrogation waived, A.M. Best A IX carrier
Proof of insurance before interconnection
Dedicated disconnect switch mounted separately from the meter socket, labeled Generator Disconnect Switch

Over 50 kW to 1 MW AC Size 50.001 to 1000 kW

Coverage rises to not less than $1,000,000 per occurrence and the City of Naperville must be named as an additional insured. A homeowner policy will often not deliver additional insured status from an A IX carrier, so this needs to be priced rather than assumed. Commercial permit fees run about $203 for a simple installation.

$1,000,000 per occurrence liability coverage with the City of Naperville named as additional insured
A.M. Best A IX carrier, primary coverage, subrogation waived
Notice to the utility within 24 hours of any cancellation or material modification

The screens that decide it

Within the 1 MW AC ceiling Limit 1000 kW.
Facilities may not be sized to exceed a one megawatt AC nameplate rating, and must additionally be reasonably sized as the utility determines. That second test is a qualitative utility discretion with no published number, so it cannot be scored.
Open ended transformer cost exposure, including after permission to operate
Before interconnection the utility advises of additional equipment including a transformer, payable in full within 60 days of invoice. More unusually, if after interconnection the utility determines additional infrastructure is needed, it may disconnect the facility until that infrastructure is installed and paid for at actual cost. Nothing caps this. Naperville publishes residential and commercial capacity maps showing whether a location can support an install or needs an upgrade, and those are worth checking before the sale.

Ask the utility this, before you sell it

What capacity does the published capacity map show at this address, and would the install trigger a utility upgrade?
What size does the utility consider reasonable here? The numeric size restrictions were removed in April 2025 and replaced by a reasonableness determination with no published figure.
How long will interconnection review and permission to operate take? Only the building permit clock is published, at ten business days to permit issuance.
Is this a lease or a power purchase agreement? Naperville recognizes only a lease at a fixed monthly fee, so a power purchase structure does not qualify as a self supply customer at all, and leased systems are ineligible for the city incentive.

Worth knowing before you quote

Net metering is open and is one for one on energy, but credits offset only the electric utility component and expressly not the meter fee or the demand charge. Credits carry over monthly, expire 31 March, and the expired balance is paid out in April at the avoided cost rate, currently 4.9 cents per kWh. No aggregate program cap, no fifteen percent screen and no minimum load test are published. Storage is inside the eligible facility definition but no non export provision is published. The utility determines in its sole discretion whether the disconnect switch and its location are suitable, and has access at all times without notice. Re roofing requires a new building permit to reinstall an existing array. On termination the customer must permanently isolate the facility at their own expense within ten working days. The agreement is between the city and the customer, with the premises owner jointly and severally liable if leased, and it contains no installer signature block, so the customer must personally execute it.

Source

City of Naperville Renewable Energy Interconnection Agreement, policy adopted April 2025, with the City of Naperville Solar Checklist 2025 revised 28 January 2025

Read and recorded 2026-09-12. Municipal or public power utility, outside its state's interconnection rule. Its own published documents govern. An Illinois municipal utility. The April 2025 policy eliminated the prior explicit size restrictions and replaced them with a 1 MW AC ceiling plus a reasonableness test.

All Illinois interconnection rules

Size bands and what each one obliges

The screens that decide it

Ask the utility this, before you sell it

Worth knowing before you quote

What to do with this