In the

United States Court of Appeals

For the Seventh Circuit ____________________

No. 16-3766

NAPERVILLE SMART METER AWARENESS,

Plaintiff-Appellant,

v.

CITY OF NAPERVILLE,

Defendant-Appellee.

____________________

Appeal from the United States District Court for the

Northern District of Illinois, Eastern Division.

No. 11 C 9299 — John Z. Lee, Judge.

____________________

ARGUED MARCH 27, 2018 — DECIDED AUGUST 16, 2018

____________________

Before WOOD, Chief Judge, and BAUER and KANNE, Circuit 

Judges.

KANNE, Circuit Judge. The City of Naperville owns and operates a public utility that provides electricity to the city’s residents. The utility collects residents’ energy-consumption 

data at fifteen-minute intervals. It then stores the data for up 

to three years. This case presents the question whether Naperville’s collection of this data is reasonable under the Fourth 
2 No. 16-3766

Amendment of the U.S. Constitution and Article I, § 6 of the 

Illinois Constitution. 

I. BACKGROUND

The American Recovery and Reinvestment Act of 2009 set 

aside funds to modernize the Nation’s electrical grid. The Act 

tasked the Department of Energy with distributing these 

funds under the Smart Grid Investment Grant program. 

Through this program, the City of Naperville was selected to 

receive $11 million to update its own grid. As part of these 

upgrades, Naperville began replacing its residential, analog

energy meters with digital “smart meters.”

Using traditional energy meters, utilities typically collect 

monthly energy consumption in a single lump figure once per 

month. By contrast, smart meters record consumption much 

more frequently, often collecting thousands of readings every 

month. Due to this frequency, smart meters show both the 

amount of electricity being used inside a home and when that 

energy is used.

This data reveals information about the happenings inside 

a home. That is because individual appliances have distinct 

energy-consumption patterns or “load signatures.” Ramyar 

Rashed Mohassel et al., A Survey on Advanced Metering Infrastructure, 63 Int’l J. Electrical Power & Energy Systems 473, 

478 (2014). A refrigerator, for instance, draws power differently than a television, respirator, or indoor grow light. By 

comparing longitudinal energy-consumption data against a 

growing library of appliance load signatures, researchers can 

predict the appliances that are present in a home and when 

those appliances are used. See id.; A. Prudenzi, A Neuron Nets 

Based Procedure for Identifying Domestic Appliances Pattern-of-
No. 16-3766 3

Use from Energy Recordings at Meter Panel, 2 IEEE Power Engineering Soc’y Winter Meeting 941 (2002). The accuracy of 

these predictions depends, of course, on the frequency at 

which the data is collected and the sophistication of the tools 

used to analyze that data. 

While some cities have allowed residents to decide 

whether to adopt smart meters, Naperville’s residents have 

little choice. If they want electricity in their homes, they must 

buy it from the city’s public utility. And they cannot opt out 

of the smart-meter program.1 The meters the city installed collect residents’ energy-usage data at fifteen-minute intervals. 

Naperville then stores the data for up to three years. 

Naperville Smart Meter Awareness (“Smart Meter Awareness”), a group of concerned citizens, sued Naperville over 

the smart-meter program. It alleges that Naperville’s smart

meters reveal “intimate personal details of the City’s electric 

customers such as when people are home and when the home 

is vacant, sleeping routines, eating routines, specific appliance types in the home and when used, and charging data for 

plug-in vehicles that can be used to identify travel routines 

and history.” (R. 102-1 at 14.) The organization further alleges

that collection of this data constitutes an unreasonable search 

under the Fourth Amendment of the U.S. Constitution as well 

 1 Residents may request that Naperville replace their analog meters 

with “non-wireless” smart meters. But these alternatives are smart meters 

with wireless transmission disabled. They collect equally rich data. The 

difference is that the data must be manually retrieved. (R. 117 at 3.)
4 No. 16-3766

as an unreasonable search and invasion of privacy under Article I, § 6 of the Illinois Constitution.2

The district court dismissed two of Smart Meter Awareness’s complaints without prejudice. Smart Meter Awareness

requested leave to file a third, but the district court denied 

that request. It reasoned that amending the complaint would 

be futile because even the proposed third amended complaint

had not plausibly alleged a Fourth Amendment violation or a 

violation of the Illinois Constitution. Smart Meter Awareness 

appealed. Because the district court denied leave to amend on 

futility grounds, we apply the legal sufficiency standard of 

Rule 12(b)(6) de novo to determine if the proposed amended

complaint fails to state a claim. See, e.g., Gen. Elec. Capital Corp. 

v. Lease Resolution Corp., 128 F.3d 1074, 1085 (7th Cir. 1997).

II.ANALYSIS

The Fourth Amendment of the U.S. Constitution protects 

“[t]he right of the people to be secure in their persons, houses, 

papers, and effects, against unreasonable searches and seizures.” Similarly, Article I, § 6 of the Illinois Constitution affords people “the right to be secure in their persons, houses, 

papers and other possessions against unreasonable searches, 

seizures, invasions of privacy or interceptions of communications by eavesdropping devices or other means.” 

We can resolve both the state and federal constitutional 

claims by answering the following two questions.3 First, has 

 

2 Smart Meter Awareness challenged the smart-meter program on a 

number of other grounds that are not relevant to this appeal.

3 The Illinois Supreme Court applies “a ‘limited lockstep’ approach 

when interpreting cognate provisions of [the Illinois] and federal constitutions.” See, e.g., City of Chicago v. Alexander, 89 N.E.3d 707, 713 (Ill. 2017)
No. 16-3766 5

the organization plausibly alleged that the data collection is a 

search? Second, is the search unreasonable? For the reasons 

that follow, we find that the data collection constitutes a 

search under both the Fourth Amendment and the Illinois 

Constitution. This search, however, is reasonable. 4

A. The collection of smart-meter data at fifteen-minute intervals

constitutes a search. 

“At the [Fourth Amendment’s] very core stands the right 

of a man to retreat into his own home and there be free from 

unreasonable government intrusion.” Silverman v. United 

States, 365 U.S. 505, 511 (1961). This protection, though previously tied to common-law trespass, now encompasses 

 

(citing People v. Caballes, 851 N.E.2d 26, 35–36 (Ill. 2006)). Under this approach, the Illinois Supreme Court will interpret a provision of the Illinois 

Constitution in the same way as a similar provision in the Federal Constitution absent certain exceptional circumstances. See Caballes, 851 N.E.2d at 

31–46 (tracing the development and application of the limited lockstep approach). Here, our analysis focuses on two terms: “searches” and “unreasonable.” These terms appear in both documents in analogous fashion. 

Neither party has “made a case for an exception to the lockstep doctrine.” 

Id. at 46. And we see no reason for an exception. Thus, our analysis of 

Smart Meter Awareness’s claim under the Fourth Amendment also resolves its claim under Article I, § 6 of Illinois Constitution. 

4 Smart Meter Awareness also claims that smart meters are an invasion of privacy under Article I, § 6 of the Illinois Constitution. It’s certainly 

possible that this is the case. But the Illinois Supreme Court conducts reasonableness balancing for the invasion of privacy under the same framework as searches under the Fourth Amendment. In re May 1991 Will Cty. 

Grand Jury, 604 N.E.2d 929, 934–35 (Ill. 1992). Even were we to find that 

the data collection was an invasion of privacy as well as a search, our reasonableness analysis for both claims would be the same. We therefore decline to conduct the additional analysis.
6 No. 16-3766

searches of the home made possible by ever-more sophisticated technology. Kyllo v. United States, 533 U.S. 27, 31–32 

(2001). Any other rule would “erode the privacy guaranteed 

by the Fourth Amendment.” Id. at 34. 

“Where ... the Government uses a device that is not in 

general public use, to explore details of the home that would 

previously have been unknowable without physical intrusion, the surveillance is a ‘search.’” Id. at 40. This protection 

remains in force even when the enhancements do not allow 

the government to literally peer into the home. In Kyllo, for 

instance, the intrusion by way of thermal imaging was relatively crude—it showed that “the roof over the garage and a 

side wall of [a] home were relatively hot compared to the rest 

of the home and substantially warmer than neighboring 

homes in the triplex.” Id. at 30. The device “did not show any 

people or activity within the walls of the structure” nor could 

it “penetrate walls or windows to reveal conversations or human activities.” Id (quoting Supp.App. to Pet. for Cert. 39–40). 

Nevertheless, the Supreme Court held that law enforcement 

had searched the home when they collected thermal images. 

Id. at 40.

The technology-assisted data collection that Smart Meter 

Awareness alleges here is at least as rich as that found to be a 

search in Kyllo. Indeed, the group alleges that energy-consumption data collected at fifteen-minute intervals reveals 

when people are home, when people are away, when people 

sleep and eat, what types of appliances are in the home, and 

when those appliances are used.5 (R. 102-1 at 14.) By contrast, 

 5 Smart Meter Awareness directed the court to academic studies 

demonstrating the revealing nature of smart-meter data collected at fifteen-minute intervals, see, e.g., Ramyar Rashed Mohassel et al., supra at 
No. 16-3766 7

Kyllo merely revealed that something in the home was emitting a large amount of energy (in the form of heat). 

It’s true that observers of smart-meter data must make 

some inferences to conclude, for instance, that an occupant is 

showering, or eating, or sleeping. But Kyllo rejected the “extraordinary assertion that anything learned through ‘an inference’ cannot be a search.” Id. at 36 (quoting id. at 44 (Stevens, 

J., dissenting)). What’s more, the data collected by Naperville 

can be used to draw the exact inference that troubled the 

Court in Kyllo. There, law enforcement “concluded that [a 

home’s occupant] was using halide lights to grow marijuana 

in his house” based on an excessive amount of energy coming 

from the home. Id. at 30. Here too, law enforcement could conclude that an occupant was using grow lights from incredibly 

high meter readings, particularly if the power was drawn at 

odd hours. In fact, the data collected by Naperville could 

prove even more intrusive. By analyzing the energy consumption of a home over time in concert with appliance load 

profiles for grow lights, Naperville law enforcement could 

“conclude” that a resident was using the lights with more 

confidence than those using thermal imaging could ever hope 

for. With little effort, they could conduct this analysis for 

many homes over many years. 

Under Kyllo, however, even an extremely invasive technology can evade the warrant requirement if it is “in general 

public use.” Id. at 40. While more and more energy providers 

are encouraging (or in this case forcing) their customers to 

 

478; A. Prudenzi, supra, and to commercially available products that can 

identify what appliances are used in a home and when they are used based 

on smart-meter data. See Disaggregation, Ecotagious, https://www.ecotagious.com/disaggregation/ (last visited July 25, 2018).
8 No. 16-3766

permit the installation of smart meters, the meters are not yet 

so pervasive that they fall into this class. To be sure, the exact 

contours of this qualifier are unclear—since Kyllo, the Supreme Court has offered little guidance. But Kyllo itself suggests that the use of technology is not a search when the technology is both widely available and routinely used by the 

general public. See id. at 39 n.6 (quoting California v. Ciraolo, 

476 U.S. 207, 215 (1986) (“In an age where private and commercial flight in the public airways is routine, it is unreasonable for respondent to expect that his marijuana plants were 

constitutionally protected from being observed with the naked eye from an altitude of 1,000 feet.”)). Smart meters, by 

contrast, have been adopted only by a portion of a highly specialized industry. 

The ever-accelerating pace of technological development 

carries serious privacy implications. Smart meters are no exception. Their data, even when collected at fifteen-minute intervals, reveals details about the home that would be otherwise unavailable to government officials with a physical 

search. Naperville therefore “searches” its residents’ homes

when it collects this data.

Before continuing, we address one wrinkle to the search 

analysis. Naperville argues that the third-party doctrine renders the Fourth Amendment’s protections irrelevant here. 

Under that doctrine, a person surrenders her expectation of 

privacy in information by voluntarily sharing it with a third 

party. See Carpenter v. United States, 138 S. Ct. 2206, 2216 (2018) 

(citing Smith v. Maryland, 442 U.S. 735, 743–744 (1979) and 

United States v. Miller, 425 U.S. 435, 443 (1976)). Thus, when a 

government authority gathers the information from the third 
No. 16-3766 9

party, it does not run afoul of the Fourth Amendment. Id. Referencing this doctrine, Naperville argues that its citizens sacrifice their expectation of privacy in smart-meter data by entering into a “voluntary relationship” to purchase electricity

from the city. 

This argument is unpersuasive. As a threshold matter, 

Smart Meter Awareness challenges the collection of the data 

by Naperville’s public utility. There is no third party involved 

in the exchange.6 Moreover, were we to assume that Naperville’s public utility was a third party, the doctrine would still 

provide Naperville no refuge. The third-party doctrine rests 

on “the notion that an individual has a reduced expectation 

of privacy in information knowingly shared with another.” 

Carpenter, 138 S. Ct. at 2219. But in this context, a choice to 

share data imposed by fiat is no choice at all. If a person does 

not—in any meaningful sense—“voluntarily ‘assume the risk’ 

of turning over a comprehensive dossier of physical movements” by choosing to use a cell phone, Carpenter, 138 S. Ct. 

at 2220 (quoting Smith, 442 U.S. at 745), it also goes that a 

home occupant does not assume the risk of near constant 

monitoring by choosing to have electricity in her home. We 

therefore doubt that Smith and Miller extend this far. 

 6 This alone renders Naperville’s reference to the Eighth Circuit’s decision, United States v. McIntyre, 646 F.3d 1107 (8th Cir. 2011), irrelevant. 

Whereas here residents contest the utility’s initial collection of the data, 

McIntrye challenged law enforcement’s subsequent warrantless collection 

of traditional meter readings from the utility. 
10 No. 16-3766

B. The data collection is a reasonable search. 

That the data collection constitutes a search does not end 

our inquiry. Indeed, “[t]he touchstone of the Fourth Amendment is reasonableness.” Florida v. Jimeno, 500 U.S. 248, 250 

(1991). Thus, if Naperville’s search is reasonable, it may collect the data without a warrant. Since these searches are not 

performed as part of a criminal investigation, see Riley v. California, 134 S. Ct. 2473, 2482 (2014), we can turn immediately to 

an assessment of whether they are reasonable, “by balancing 

its intrusion on the individual’s Fourth Amendment interests 

against its promotion of legitimate government interests.” 

Hiibel v. Sixth Judicial Dist. Court, 542 U.S. 177, 187–88 (2004) 

(quoting Delaware v. Prouse, 440 U.S. 648, 654 (1979)). Although in this case, our balancing begins with the presumption that this warrantless search is unreasonable, see Kyllo, 533 

U.S. at 40, Naperville’s smart-meter ordinance overcomes this 

presumption.

Residents certainly have a privacy interest in their energyconsumption data. But its collection—even if routine and frequent—is far less invasive than the prototypical Fourth 

Amendment search of a home. Critically, Naperville conducts 

the search with no prosecutorial intent. Employees of the 

city’s public utility—not law enforcement—collect and review the data. 

In Camara v. Municipal Court, the Supreme Court noted 

that this consideration lessens an individual’s privacy interest. 387 U.S. 523, 530 (1967). And though the Court held that 

a warrantless, administrative, home inspection violated the 

Fourth Amendment in that case, it did so based on concerns 

largely absent from this one. Id. at 530–31. Indeed, unlike the 

search in Camara, Naperville’s data collection reveals details 
No. 16-3766 11

about the home without physical entry. See id. at 531 (highlighting the “serious threat to personal and family security” 

posed by physical entry). Moreover, the risk of corollary prosecution that troubled the court in Camara is minimal here. See 

id. (noting that “most regulatory laws, fire, health, and housing codes are enforced by criminal process.”). To this court’s 

knowledge, using too much electricity is not yet a crime in 

Naperville. And Naperville’s amended “Smart Grid Customer Bill of Rights” clarifies that the city’s public utility will 

not provide customer data to third parties, including law enforcement, without a warrant or court order. Thus, the privacy interest at stake here is yet more limited than that at issue in Camara. 

Of course, even a lessened privacy interest must be 

weighed against the government’s interest in the data collection. That interest is substantial in this case. Indeed, the modernization of the electrical grid is a priority for both Naperville, (R. 120-1, Smart Meter Agreement between Naperville 

and the Department of Energy), and the Federal Government,

see Smart Grid, Federal Energy Regulatory Commission (Apr. 

21, 2016), https://www.ferc.gov/industries/electric/indusact/smart-grid.asp.

Smart meters play a crucial role in this transition. See id. 

For instance, they allow utilities to restore service more 

quickly when power goes out precisely because they provide 

energy-consumption data at regular intervals. See, e.g., Noelia 

Uribe-Pérez et al., State of the Art and Trends Review of Smart 

Metering in Electricity Grids, 6 Applied Sci., no. 3, 2016, at 68, 

82. The meters also permit utilities to offer time-based pricing, 

an innovation which reduces strain on the grid by encourag-
12 No. 16-3766

ing consumers to shift usage away from peak demand periods. Id. In addition, smart meters reduce utilities’ labor costs 

because home visits are needed less frequently. Id.

With these benefits stacked together, the government’s interest in smart meters is significant. Smart meters allow utilities to reduce costs, provide cheaper power to consumers, encourage energy efficiency, and increase grid stability. We 

hold that these interests render the city’s search reasonable, 

where the search is unrelated to law enforcement, is minimally invasive, and presents little risk of corollary criminal 

consequences. 

We caution, however, that our holding depends on the 

particular circumstances of this case. Were a city to collect the 

data at shorter intervals, our conclusion could change. Likewise, our conclusion might change if the data was more easily 

accessible to law enforcement or other city officials outside 

the utility.

III. CONCLUSION

Naperville could have avoided this controversy—and 

may still avoid future uncertainty—by giving its residents a 

genuine opportunity to consent to the installation of smart 

meters, as many other utilities have. Nonetheless, Naperville’s warrantless collection of its residents’ energy-consumption data survives our review in this case. 

Even when set to collect readings at fifteen-minute intervals, smart meters provide Naperville rich data. Accepting 

Smart Meter Awareness’s well-pled allegations as true, this 

collection constitutes a search. But because of the significant 
No. 16-3766 13

government interests in the program, and the diminished privacy interests at stake, the search is reasonable. We therefore 

AFFIRM the district court’s denial of leave to amend.