                               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 op-
erates a public utility that provides electricity to the city’s res-
idents. 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 Naper-
ville’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 Infra-
structure, 63 Int’l J. Electrical Power & Energy Systems 473,
478 (2014). A refrigerator, for instance, draws power differ-
ently 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 Engi-
neering 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 col-
lect residents’ energy-usage data at fifteen-minute intervals.
Naperville then stores the data for up to three years.
    Naperville Smart Meter Awareness (“Smart Meter Aware-
ness”), 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 appli-
ance 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 Ar-
ticle I, § 6 of the Illinois Constitution. 2
    The district court dismissed two of Smart Meter Aware-
ness’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 sei-
zures.” Similarly, Article I, § 6 of the Illinois Constitution af-
fords people “the right to be secure in their persons, houses,
papers and other possessions against unreasonable searches,
seizures, invasions of privacy or interceptions of communica-
tions 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 consti-
tutions.” 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 previ-
ously tied to common-law trespass, now encompasses



(citing People v. Caballes, 851 N.E.2d 26, 35–36 (Ill. 2006)). Under this ap-
proach, the Illinois Supreme Court will interpret a provision of the Illinois
Constitution in the same way as a similar provision in the Federal Consti-
tution absent certain exceptional circumstances. See Caballes, 851 N.E.2d at
31–46 (tracing the development and application of the limited lockstep ap-
proach). Here, our analysis focuses on two terms: “searches” and “unrea-
sonable.” 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 re-
solves its claim under Article I, § 6 of Illinois Constitution.
    4  Smart Meter Awareness also claims that smart meters are an inva-
sion 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 rea-
sonableness balancing for the invasion of privacy under the same frame-
work 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 rea-
sonableness analysis for both claims would be the same. We therefore de-
cline to conduct the additional analysis.
6                                                         No. 16-3766

searches of the home made possible by ever-more sophisti-
cated 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 intru-
sion, 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 rela-
tively 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 hu-
man 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-con-
sumption 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 fif-
teen-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 emit-
ting 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 “ex-
traordinary assertion that anything learned through ‘an infer-
ence’ 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 con-
clude 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 con-
sumption 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 tech-
nology 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.eco-
tagious.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 Su-
preme Court has offered little guidance. But Kyllo itself sug-
gests that the use of technology is not a search when the tech-
nology 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 com-
mercial flight in the public airways is routine, it is unreason-
able for respondent to expect that his marijuana plants were
constitutionally protected from being observed with the na-
ked eye from an altitude of 1,000 feet.”)). Smart meters, by
contrast, have been adopted only by a portion of a highly spe-
cialized industry.
    The ever-accelerating pace of technological development
carries serious privacy implications. Smart meters are no ex-
ception. Their data, even when collected at fifteen-minute in-
tervals, reveals details about the home that would be other-
wise 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 ren-
ders 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. Ref-
erencing this doctrine, Naperville argues that its citizens sac-
rifice their expectation of privacy in smart-meter data by en-
tering 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 Naper-
ville’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 move-
ments” 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 de-
cision, 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 Amend-
ment is reasonableness.” Florida v. Jimeno, 500 U.S. 248, 250
(1991). Thus, if Naperville’s search is reasonable, it may col-
lect the data without a warrant. Since these searches are not
performed as part of a criminal investigation, see Riley v. Cali-
fornia, 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)). Alt-
hough in this case, our balancing begins with the presump-
tion 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 energy-
consumption data. But its collection—even if routine and fre-
quent—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 re-
view the data.
    In Camara v. Municipal Court, the Supreme Court noted
that this consideration lessens an individual’s privacy inter-
est. 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 (high-
lighting the “serious threat to personal and family security”
posed by physical entry). Moreover, the risk of corollary pros-
ecution that troubled the court in Camara is minimal here. See
id. (noting that “most regulatory laws, fire, health, and hous-
ing 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 Cus-
tomer Bill of Rights” clarifies that the city’s public utility will
not provide customer data to third parties, including law en-
forcement, without a warrant or court order. Thus, the pri-
vacy interest at stake here is yet more limited than that at is-
sue in Camara.
    Of course, even a lessened privacy interest must be
weighed against the government’s interest in the data collec-
tion. That interest is substantial in this case. Indeed, the mod-
ernization of the electrical grid is a priority for both Naper-
ville, (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/indus-
act/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 peri-
ods. 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 in-
terest in smart meters is significant. Smart meters allow utili-
ties to reduce costs, provide cheaper power to consumers, en-
courage 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 mini-
mally 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. Like-
wise, 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, Naper-
ville’s warrantless collection of its residents’ energy-con-
sumption data survives our review in this case.
    Even when set to collect readings at ﬁfteen-minute inter-
vals, 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 pri-
vacy interests at stake, the search is reasonable. We therefore
AFFIRM the district court’s denial of leave to amend.
