
Monitoring Home Power Consumption for less than $25 - robbiet480
https://blog.kroy.io/monitoring-home-power-consumption-for-less-than-25/
======
linker3000
* OWL power monitor with inductive clamp and separate LCD display (in the reduced bin at the local DIY barn), transmits data on 433MHz - £12

* Arduino Mega+ESP8266 combo board - £8

* Rflink Rx/TX board - order a kit or build your own ([http://www.rflink.nl/blog2/wiring](http://www.rflink.nl/blog2/wiring)) 433 or 868MHz operation, can also work with some devices at 2.4GHz - About £15

* Rflink software ([http://www.rflink.nl/blog2/](http://www.rflink.nl/blog2/)) + Serial link software for the ESP8266 - all free.

* Configure the serial link software to talk to your MQTT broker (Raspberry Pi running Mosquitto and Node-Red)

You now have an rf receiver/transmitter system that can not only pick up and
display your energy monitor signals, but also those of many other rf devices
AND can record/re-transmit such signals too - in my case, I can get an alert
when the doorbell rings + Capture shots from an IP camera, plus I can control
a bunch of those cheap, remote controlled rf mains power sockets I've
collected over the years.

Not as cheap as the SDR option, but with much more functionality

~~~
lucaspiller
You can also buy clamp sensors that can be connected directly to a
microcontroller (with an ADC - so not a Raspberry Pi without external
hardware).

[http://www.homautomation.org/2013/09/17/current-
monitoring-w...](http://www.homautomation.org/2013/09/17/current-monitoring-
with-non-invasive-sensor-and-arduino/)

~~~
PoachedSausage
The clamp only systems lack accuracy due to not measuring supply voltage.
Commercial/open source energy meters based on chips like the ADE7953[0] have a
resistive voltage divider to attenuate the supply voltage to suitable level
for the chip but preserving the envelope for sampling. The problem is there is
no galvanic isolation, so interfacing is harder.

[0] [http://www.analog.com/en/products/analog-to-digital-
converte...](http://www.analog.com/en/products/analog-to-digital-
converters/integrated-special-purpose-converters/energy-metering-
ics/ade7953.html#product-overview)

~~~
calmconviction
I have a similar set up with a Z-wave clamp style current meter[0]. This meter
is calibrated to 120v. I use NUT to grab the line voltage off the UPS and
adjust the reported current with actual voltage to get power. It's good enough
for the girls I go out with

[0] [https://www.amazon.com/Aeon-Labs-AEDSB09104ZWUS-Aeotec-
Monit...](https://www.amazon.com/Aeon-Labs-AEDSB09104ZWUS-Aeotec-
Monitor/dp/B00DIBSKFU)

~~~
AdamJacobMuller
I have the same meter, that meter actually reports voltage to me though.

------
SergeAx
It is extremely strange they don't use even primitive encryption. I work for
Russian company "Strizh Telematics", we are making smart resource meters. We
take security very seriously here: all transmits are encrypted with 64 bit
keys and data protocols are specifically protected from statistical and
repeat-packet attacks.

~~~
wcoenen
Why 64 bit? The minimum key strength supported by AES is 128 bits, so 64 bits
seems very low.

~~~
SergeAx
To reduce power consumption by using simple hardware. See my answer to @mrb
above.

------
spyder
_" Some research told me that the power company accomplishes this via a simple
radio broadcast on the 900Mhz spectrum."_

So, will there be a website similar to flightradar24 but for meter readings on
a map? :)

~~~
simooooo
Electricity meter war driving?

------
Mister_Snuggles
Reading this piqued my interest as this is something I’ve wanted to do ever
since my local electric company started to roll out smart meters.

I took a look at my electric company’s web site to see what kind of meters
they use and it turns out that they have already seen this need. They will
enable the ZigBee module in the meters and set it up to talk to a home energy
monitoring device (which you have to buy separately)[0]. The fact that this is
officially sanctioned is pretty cool!

Once of the devices, the Rainforest Eagle, even has API documentation[1] so
that you can build this type of thing, but with real-time data. The best part,
from my point of view, is that they expose an API via their Cloud service AND
have a local API on the device itself. It’s possible, though I have no way to
know this without buying one, that you may even be able to use it completely
independent of their Cloud service. So far the only limitation I’ve found
while reading the docs is that you seem to need the Cloud service to configure
the Push API, but I didn’t notice that limitation with the Pull API.

[0] [https://www.epcor.com/learn/meters/advanced-
meters/Pages/hom...](https://www.epcor.com/learn/meters/advanced-
meters/Pages/home-energy-monitors.aspx)

[1]
[https://rainforestautomation.com/support/developer/](https://rainforestautomation.com/support/developer/)

~~~
phubbard
I built a purely local version using the Raven USB Zigbee modem, flask and
D3.js. Crude, uses SQLite but might be of interest. The XML decoding is only
hard part really.

[https://github.com/phubbard/raven-peewee](https://github.com/phubbard/raven-
peewee)

~~~
Mister_Snuggles
Cool!

Did you have any trouble convincing your utility company to enable the ZigBee
module? Or do they do things differently?

~~~
phubbard
It was no problem at all - online form on the SDGE site.

------
cbr

        I am bombarded with ads on Facebook for the Sense. This
        device allows you to monitor whole-home power
        consumption. ... I realized it would be extremely simple
        to do something similar without any wires or hassle.
    

Sense monitors two things:

* instantaneous current

* instantaneous voltage

Different devices have different electrical signatures, and this allows it to
learn what devices you have in your house. RTL-SDR is much too low-resolution
for this.

RTL-SDR monitoring would actually be awesome to add to Sense: the method it
uses for measuring current is designed for microsecond-level accuracy, not
long-term accuracy like your meter. So over time they won't keep perfectly in
sync. If Sense could automatically read your meter it could calibrate itself.

~~~
collinmanderson
I've been recording my power and gas usage via RTL-SDR for over a year. You
only get a data point a few times a minute (if that). However, I can usually
(though not always), with context, tell that a big spike was my hot water
heater vs air conditioner, etc.

(Though it's not enough to get totals for the day/month/year per appliance.)

~~~
AdamJacobMuller
What are you using for reading your gas meter?

~~~
collinmanderson
I'm getting both with the same antenna. Both meters have Itron brand
transmitters.

------
masklinn
> Some research told me that the power company accomplishes this via a simple
> radio broadcast on the 900Mhz spectrum.

Interesting. Around here (mainland Europe) they're currently installing
"smart" meters which do this using CPL rather than radio.

> And with one simple command, I was reading the power (and probably water)
> meters for my entire neighborhood

That is a bit troubling from a _physical_ security perspective, once you've
mapped meters to accommodation you can now remotely check for _presence_
across an entire neighbourhood, and can ignore the usual "fake presence"
indicators (randomised lighting & blinds manipulation) entirely. In fact those
would help you as seeing lights in a house whose owners are on holidays would
not surprise the neighbours.

~~~
JohnMort
What about thieves going around selecting data and pinpointing the house the
one with the least consumption so they can find out if you are absent or not.
Incredible techonology

~~~
masklinn
That's what my second paragraph is talking about.

Note that "least consumption" is not the right indicator, different people
have different levels of consumption. What you want is a break in the
consumption pattern, a home with _lower than usual_ consumption of
electricity.

~~~
Heliosmaster
You just need to build a baseline: hide a device and record activity over a
long-ish period of time and then it's easier to sense patterns

~~~
jdavis703
Unless your house has something very valuable, I kind of doubt most thieves
would spend this much time plotting to break in.

~~~
masklinn
They don't need to spend any time on it past the initial setup, you can have
an automated system integrating the consumption pattern of an entire
neighbourhood, and pointing out which owners are likely on holidays.

------
icelancer
>>I use PHP. There, I admitted it.

Very happy to see stuff like this in blog posts. I use it all the time to
stand up scripts like this. It makes me REALLY happy to see hacky code like:

>>exec("/scripts/gocode/bin/rtlamr -msgtype={$type} --format=json
--filterid={$unitid} --single=true",$output);

I also do this all the time, even to control Windows processes on client/slave
machines (generally killing and relaunching stalled programs).

~~~
ahoka
The problem that it takes a $type="; rm -rf /" to ruin your day.

~~~
icelancer
No doubt, that's why stuff like this should be limited to internal tooling and
private use only, not exposed to the Internet. When done that way, it's just
infinitely more efficient to write trash code in PHP for one-off things, and
there's literally nothing wrong with it when it has an audience of 1 -
yourself.

Beyond that, yeah, you shouldn't do things like that. But there is no reason
to stand up an entire test suite and development environment just to write
some stuff to check power usage or internal sensors in your house.

(also that command would fail on the machines I run my crap code on, Win10
discardable VMs)

------
PostOnce
Tangential, but what other fascinating things can I do with an SDR dongle?
I've had one for years and have not heard of this.

* Listen to various radio stations

* Track airplane positions

* Receive weather images from a satellite

what else?

One other thing off the top of my head is combining ship position and cargo
databases: [https://github.com/marcdacosta/ambient-
shipping](https://github.com/marcdacosta/ambient-shipping)

~~~
jstanley
You can use an upconverter and listen to shortwave radio, but you'll need a
much larger antenna.

You can receive and decode "POCSAG" and "FLEX" pager messages.

You can receive and decode messages from all sorts of 433MHz wireless devices
(doorbells, car keys, thermostats).

You can use a downconverter and receive the bitcoin blockchain from
blockstrean satellite, but you'll need a dish and some other equipment too.

It's a surprisingly versatile bit of kit.

------
jvandonsel
Pedantic engineering correction. The units are "watt-hours" or "watt hours",
not watt/hours.

------
problems
Nice method, but for future record you don't really need to mess with mains to
hook up Sense or OpenEnergyMonitor, they use inductive current clamps which
work by detecting the field around the a single terminal of your incoming
mains. Pretty much as safe as it gets with this stuff.

~~~
evan_
Sense actually has you install a 240v breaker in addition to the clamps.

[https://sense.com/help/installguide.pdf](https://sense.com/help/installguide.pdf)
[https://youtu.be/qh9m2xuDrW4](https://youtu.be/qh9m2xuDrW4)

------
disillusioned
This is neat. I had vaguely heard of the RTL-SDR, but this is a cool example
of a potential application.

A few points of note:

The author starts off by discussing how the Sense energy monitor piqued his
interest, but he didn't want to go through the trouble of installing it. My
understanding is that Sense offers granular usage data down to the appliance
level, which reading polled usage off the meter simply won't do. So this isn't
a solution that replaces what Sense offers.

And... doesn't your power company already offer you this data? APS here in
Arizona does, down to the hour, with the ability to easily export as CSV. But
I'm sure plenty of utilities don't offer that, and this is a cool way to read
it.

~~~
collinmanderson
> reading polled usage off the meter simply won't do

(I'm duping this comment from above) I've been recording my power and gas
usage via RTL-SDR for over a year. You only get a data point a few times a
minute (if that). However, I can usually (though not always), with context,
tell that a big spike was my hot water heater vs air conditioner, etc.

------
alkonaut
Is it really required to actually read currents to achieve the power
measurement? do meters in individual buildings not have interval-flashing
LED's for power consumption in the US (I'm assuming the target market is the
US)?

A flashing LED is neat because you can then use a very simple-to-install
adhesive photodiode to count the flashes and radio the results back to some
reader (e.g. 1000 impulses per kWh). Doesn't require an electrician because
you never actually tamper with the meter, unless you want to leech a tiny bit
of power to your transmitter.

The normal connection here is a big outdoor box for the incoming line, with 3
main fuses, one for each phase. Typically 3x25A @ 230V for a detached home
(Max ~17kW). This is where you want to read the power consumption. Inside the
house there is a box with 3 DIN rails (1 per phase) with switch type fuses.
With 3 phases it's a lot harder to read the power consumption there than it is
at the outside main fuse box (which is unfortunate, because it's a lot more
convenient to mount a meter indoors and near a wall socket, than outside
inside a thick steel box without easily accessible power for your power
meter+radio).

~~~
emilburzo
Would nobody bat an eye if you had an electronic device attached to the meter?
(especially the guy that comes and does the meter reading)

~~~
alkonaut
No, the meter is sealed, which is the benefit of this type of arrangement. The
meter just sits attached to the meter on the outside, so it's obvious that
nothing is tampered with. Many power companies even sell their own (branded)
kits that does this.

It's also very rare to have someone come read the meter. Like all other parts
of society anything that can be automated at almost any cost has been already.
I have had no one read water or power meters for many years.

~~~
emilburzo
> I have had no one read water or power meters for many years.

Ah, that makes more sense now :)

Over here we still have people that come to read the meters every 3 months.

~~~
pbhjpbhj
In the UK they use estimated readings, primarily it seems as a way to borrow a
pretty large amount from their customers - they appear to "estimate" at 20%
above actual rates. Evil, but pretty clever.

------
raesene9
In the UK I just use one of these
[https://loopenergysaver.com/](https://loopenergysaver.com/)

You connect the reader around the mains supply cable, plug the other end into
an Ethernet port and it works. No monthly subscription charges, just the
initial cost of the device which is £60 at the moment.

Not the most high tech solution but seems to work pretty reliably

~~~
mattmanser
In the UK we have smart meters now[1]. They tell me how much I'm using at any
time for free. Why not just use one of them? Or are they not in your area yet.

To be honest, having had one, anything that makes water hot is expensive,
everything else is cheap. Before winter hit I was using a 1/5th the
electricity I am now (useless storage heaters). TVs, computers, etc. are not
worth really worrying about.

Although, even then, boiling a kettle for a cuppa is like 1 pence, but my hot
water costs like 40p per day and my heating like £4.

[1] [https://www.gov.uk/guidance/smart-meters-how-they-
work](https://www.gov.uk/guidance/smart-meters-how-they-work)

~~~
jstanley
> Why not just use one of them?

Because you don't want your electricity meter to have the ability to be
remotely-instructed to disconnect your electricity supply, and you don't want
your electricity meter to have the ability to record fine-grained data about
your electricity usage patterns, which it is required to store for 13 months,
and which you can't actually know for sure isn't sent off remotely even if you
opt out of that.

I am interested in having a device in my home telling me how much electricity
I'm using in real-time, but not if it comes bundled with a load of
surveillance and the ability to remotely disconnect my supply.

~~~
rootw0rm
I'm from California, where they can justify a raid based on your power usage.
"You're using twice as much power as your neighbors, you must be growing
cannabis indoors!".

I can definitely say you are justified in your skepticism regarding the
utility-provided equipment.

------
daenney
I do something similar at home. However, the meter in my house has a LED that
blinks per Wh used, so all I did is put something light sensitive on top of
it, wire it to a tiny board of your choice (GPIO on a Raspberry Pi in this
case) and then export the data from there. I run a tiny Prometheus exporter on
that same Pi which gets scraped and everything neatly shows up in Grafana.

For other devices I use Z-wave powered sockets which do power metering, which
is exposed by another Prometheus exporter. Since those Z-Wave sockets can be
on the expensive side I only really use them in places I want to meassure,
like my desk (which has laptop, screen etc.) or the TV.

~~~
marcins
This gets challenging when you have solar export and a bidirectional meter.
The light blinks for every _absolute_ kWh. That is, you don’t know if that was
imported or exported electricity, so you need additional information. One
approach I’ve seen is to use current clamps just to work out the difference
between what’s coming out of the solar inverter, and what’s going into the
house. If a > b then the blinks are export, and vice versa.

------
edejong
Since the transmission is not authenticated, I wonder if it is possible the
shield or interfere with your own transmission and broadcast a fake report
instead.

~~~
mkempe
Or the reports of others in the neighborhood... How does the power utility
collect these reports?

------
aequitas
"I'm not going to lie. It felt weird polling the meter readings for the entire
neighborhood."

Yikes, and I though we had it bad here in the Netherlands where you explicitly
needed to opt-out of your power supplier being able to read your meter.

At least here it is ordered that if these newer 'smart meters' are to be
installed they always need to include a 'P1 port' which allows the home owner
to simply read out the metrics every 10 seconds using a serial device.

~~~
marcins
Wish that an accessible real-time port was required here in Australia. Best I
can do is download the 30minute interval data from my electricity retailer
after the meter sends them overnight (or use other hacks like reading the
blinks)

------
tasty_freeze
I have five or six different RTL-SDR dongles that are looking for something to
do, so I am interested in this project. But it seems that I have to install a
GO ecosystem on my computer in order to compile and run the program. That is a
step too far for me in order to just kick the tires.

Does anyone know of a prebuilt windows binary for this? (I have always heard
that is one of the strengths of GO -- it produces a simple standalone binary)

[edit: I'm really referring to rtlamr, not the project described in the post.
first I would want to get rtlamr running before attempting to get the datebase
/ presentation program running]

------
chiefalchemist
Correct me if I'm wrong but open (read: unencrypted) radio signals across
public airways are not subject to any sort of protection under the law. Point
being, the police could do this legally.

------
spegelref
On the part where the author went on finding his own meter, couldn't one put a
enclosing metal mesh cage around the meter and put an antenna inside this
cage?

~~~
rootw0rm
yah, if you want to learn how difficult it is to properly shield RF.

------
kpil
I can get all my data from my power company. There is a webpage with realtime
statistics and supposedly there's an API that I never tried.

------
yummybear
I would think it would be a bit of a security hole to have anyone read your
meter. You'd easily be able to determine who is on vacation for instance. I'm
guessing you might also be able to deduce a lot of information such as
bedtimes, when you are doing laundry, when you leave for work, etc.

~~~
dawnerd
I feel like that'd be a lot more work than just watching their house for
activity.

~~~
masklinn
Sure but for theft it's much more useful to have information about an entire
neighbourhood at once, there's a much larger ROI to casing dozens or hundreds
of homes at once than to casing each one individually.

You can have "small hands" doing the initial survey (e.g. triangulate signal
strengths to meter locations), automate the surveillance/pattern checking, and
call in more professional break-in teams when you have high confidence.

------
myrandomcomment
My first thought was this is cool. Second, I should do this also. Third, hey I
can just login to PGE and see this data already, dang it, abort. :) They
cannot keep the power on in the slightest wind storm, but at least I know how
much power I am not using at that time.

------
cappie013
In Australia we don't need that: our electricity suppliers give that info on
their website :)

------
dmateos
Useful for finding the 12/12 or 18/6 pattern spikes of a weed grow house
also.. `

~~~
ozim
Still easier to do thermal camera search, you don't have to find which address
it actually is.

------
collinmanderson
I'm late to the discussion, but I've been monitoring via RTL-SDR and rtlamr
for over a year, so I figure I should weigh in. In general it was super easy
to do.

\- First, check to be sure your meter is compatible. (My gas and electric are
both Itron)
[https://github.com/bemasher/rtlamr/blob/master/meters.csv](https://github.com/bemasher/rtlamr/blob/master/meters.csv)
I recommend taking a photo of your meter. (helpful for reference and comparing
numbers)

\- Next buy the antenna and dongle. Probably obvious, but I tried buying one
with out the antenna and it wasn't good enough, so I had to modify an old wifi
router antenna to make it work. I just searched amazon for rtl-sdr.

\- Once it arrives, plug it in and install the rtlsdr software/driver. I think
this may have involved installing a kernel module, but I didn't run into any
trouble on linux. (I used pre-compiled binaries for my old 64-bit laptop
running Ubuntu 16.04) You can test things by picking up fm radio via rtl_fm.

\- Next, install golang, and "go get rtlamr".

\- To monitor, you first start rtl_tcp and let it run in the background, and
then run rtlamr which connects (via tcp) to rtl_tcp to tune the device and get
raw output.

\- The dongle can get pretty warm/hot.

\- My meter has the meter number printed right underneath a big barcode. The
first two digits are 12 or 05 for the meter type. I found this to be a pretty
easy way to find the meter.

\- My meter broadcasts two extra decimal places, so if the meter display says
123456 kwh, it actually broadcasts 12345678 (I appreciate the extra
precision). When processing things, I just add a 0 on the end to make it watt-
hours. (This is true for gas too.)

\- I get a reading from my power meter every few seconds. About once a minute
for gas.

\- I log all of my meter readings and append to a giant ~700mb CSV file.

\- I have a once-a-minute cron job that computes per-minute usage for the last
48 hours. (I save that to a static file and then graph using nginx +
javascript. I started out by graphing using excel/numbers)

\- I also have a daily cron job that computers per-day usage going back to
October 2016.

I keep rtlamr and rtl_tcp running using systemd. The rtlamr command I use is:
/home/collin/bin/rtlamr -filterid=543xxxxx,490xxxxx -format=csv -quiet >>
/home/collin/data.csv

------
heywire
rtlamr is awesome. I use it to monitor my gas meter (which is going crazy
lately with the low temps here in Ohio).

I had started a project [1] to read my water and electric meters, but just
about the time I started figuring out the protocol, they upgraded the firmware
and turned on encryption. Luckily the encryption seems to only affect the
power meter, as I am still able to read the water meter (though I’m not sure
how long that will last)

[1]
[https://github.com/shaunhey/ea_receiver](https://github.com/shaunhey/ea_receiver)

------
inglor
It's weird that he didn't give the ELK stack a chance. Kibana would be awesome
at graphing this and data ingestion would also be very simple.

Very useful for automatically generating graphs based on data. Would have
automated the whole "writing PHP + jQuery + SQLITE3" part entirely - and
consume the JSON directly and created visualizations based on that.

~~~
alanfranzoni
Do you realize that an ELK stack has an enormous overhead comparing to a bare
php script? Your idea may be good for a large-scale monitoring deployment, but
it's totally overengineered for a simple, in-house monitoring system.

------
tzs
How does the power company actually get the information transmitted by the
meter?

One of the articles the author links to says that it is collected by the power
company sending someone with an appropriate receiver to drive around
collecting the data.

However, my power company website lets you look up your usage on their
website, and that is updated daily which makes me seriously doubt that there
are any manual steps in its collection. In particular, it gets read on those
occasions every few years when we get enough snow to close down traffic on
side streets like mine.

My meter is at least 11 years, and appears quite old fashioned--it's got the
spinning disc to show instantaneous usage and analog dials to display the
cumulative usage.

I'm not actually sure that my meter has remote read capability. I read
somewhere that some power companies add remote reading to older installations
by putting something on the pole where the lines to a particular house branch
off.

There are some mysterious signals in the 900 MHz neighborhood that show up on
my SDR. I've seen them at 929.616, 929.664, 929.940, 931.066, 931.216,
931.865, and 931.942 MHz, and have not been able to figure out what they are
from. Mostly, they consist of periodical short (about 1 second) bursts of
something digital followed a few seconds later by a longer burst (several
seconds), then silence for maybe a minute, and then repeat.

Some seemed to be in pairs, where one would send a short burst, then another
would send a long burst. I suspected that this may have been my "Weather
Channel" weather meter, which has an outdoor sensor and an indoor display, and
operates in the 900 MHz area. I suspected the short burst was the indoor unit
asking the sensor for a report, and the sensor responding. I ruled that out,
though, by taking the batteries out of the indoor unit and seeing no change in
the signal pair.

It's been a while since I looked at these, and so I took another look--and now
I don't see that apparent pair. I'm not thinking that that one wasn't two
things talking to each other, but two separate things that just happened to
have their reports lined up so that it looked like they were talking to each
other.

I had guessed that they might be power meters, but I have not been able to
find anything that looks like it could be the receiver for them. I don't see
anything on the poles around here other than the usual transformers, and we
don't have any evident equipment pedestals. The signals don't seem very
strong, so I've been assuming that whatever they are talking to cannot be far
away. That made power meters seem less likely.

~~~
collinmanderson
I think my power company drives pickup trucks around once a month. (and I
don't have daily access to readings, so I log the data myself via RTL-SDR.)

Other companies / meters will create a mesh network and rebroadcast all data
back to the utility company. (I don't believe mine does that.)

------
eltoozero
Excellent, I was about to go the route of reading the led flashes with some
kind of sensor but I was reminded that anything touching the meter can be
considered meter tampering in the US which is a crime...yikes.

Thankfully passively decoding its RF emissions from the garage isn’t illegal
yet!

So HN, which SDR dongle should I buy?

~~~
xdeqx366
[https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/](https://www.rtl-
sdr.com/buy-rtl-sdr-dvb-t-dongles/)

------
qaq
I wonder if there are people who abuse this to reduce their bill or to run up
someone else's bill.

------
yeswecatan
I'm not familiar with the RTL-SDR. Why would one use that to monitor
temperature/humidity over something like an arduino + sensors?

------
JSONwebtoken
I hadn't heard of the company Sense before I read about this blog. I looked up
their product... 300 bucks, are you kidding me? And it requires licensed
installation on top of that, so maybe even more in labor. Who's buying this
stuff and how is their margin defensible from Tesla or somebody selling
Raspberry Pi kits for $25?

~~~
kabes
Of course the people without the technical skills, but also everybody who
counts their time in terms of money. I used to reason like you when I was a
student and had seemingly unlimited time on my hands. But now I'm a consultant
who bills by the hour which makes me somehow always translate time into money.
If I bill $100/hour and the raspberry PI solution would take me a day to set
up and working, then buying the sense is $500 cheaper.

~~~
rthille
Sense looks really attractive to me, except the part where they get all the
data. If they had a self hosted solution that I could run on a Raspberry Pi or
even a “real”computer to do the data collection and processing, I’d be in.

