## Facts

- The City of Naperville, Illinois owns and operates a municipal electric utility serving residents.
- Using federal funding to modernize its electrical grid, the City replaced analog meters with mandatory digital “smart meters.”
- Unlike monthly aggregate readings from analog meters, the smart meters recorded electricity usage in 15-minute intervals, yielding thousands of readings per month, and the City stored the data for up to three years.
- Granular usage data can permit inferences about in-home activity because appliances have distinct electricity “load signatures” that can indicate which devices are present and when they are used.
- Customers could not opt out of smart-meter installation; some could request a non-wireless meter, but it still collected smart-meter data (with wireless transmission disabled).
- A resident group alleged the collection and retention of this data violated the Fourth Amendment and the Illinois Constitution’s search-and-seizure provision.

## Issues

1. Whether mandatory collection of residential electricity-usage data at 15-minute intervals through smart meters constitutes a “search” under the Fourth Amendment (and the Illinois Constitution).
2. If it is a search, whether the program is reasonable under the Fourth Amendment.

## Decision

- The Seventh Circuit affirmed dismissal of the complaint.
- The City’s collection of 15-minute interval smart-meter data from homes constituted a Fourth Amendment search because it can reveal details about activities inside the home and residents lacked a meaningful ability to refuse collection.
- The search was reasonable because the program served administrative, non-law-enforcement objectives (grid modernization), involved 15-minute interval data rather than real-time monitoring, and was subject to limits on law-enforcement access (no showing of warrantless sharing).
- The same result applied to the Illinois constitutional claim on the facts presented.

## Legal Principles

- Government acquisition of sufficiently granular, time-stamped household utility-usage data can be a Fourth Amendment “search” when it enables inferences about in-home activity.
- The home receives heightened Fourth Amendment protection; methods that meaningfully expose information about the home’s interior implicate reasonable expectations of privacy.
- A program’s mandatory nature and monopoly-like practical compulsion can strengthen the privacy interest in data generated by essential services.
- Even when government action is a search, it may be reasonable without a warrant under a balancing approach when conducted for administrative purposes rather than ordinary criminal investigation, particularly where collection is limited in precision and law-enforcement access is constrained.
- Reasonableness may depend on operational details; more frequent reporting, real-time monitoring, or directed law-enforcement use could alter the balance.

## Conclusion

The court held that mandatory 15-minute interval smart-meter data collection by a municipal utility is a Fourth Amendment search because it can reveal information about in-home activities, but it was reasonable given the program’s administrative purpose, the level of detail collected, and limits on law-enforcement use, so no constitutional violation was shown.


Naperville Smart Meter Awareness v. City of Naperville, 900 F.3d 521 (7th Cir. 2018)