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Community and Q&A

Affordable, Accurate, and Easy-to-Install Energy Monitoring Systems

user-5946022 | Posted in Green Products and Materials on

[List below edited to add other sensors mentioned in comments and questions added]

ETA: For true power (not current) monitoring it seems down to two cost effective options:

-IotaWatt seems to get the vote of users for best combination of features/cost, and it is open source, but limited to 12 CT’s.
-EmporiaVue 2nd Gen seems best from an initial cost perspective,  and it allows 16 CT’s.
Trying to determine which, if any, energy monitoring system would be best.  Goal would be to troubleshoot Mitsu Ducted Mini system, but may want to use and/or expand the system in the future for other energy efficiency optimization and when I get solar.

I’ve seen the below on this site and would appreciate feedback, particularly if certain solar products only work with certain monitoring products.  Goal is a very low cost start to monitor only HVAC, expandable to future whole house monitoring & solar, open source with no monthly subscriptions, wifi & smart home option if possible.

Q1: Which accurately measure power used by  inverter type ducted minisplit systems?
Q2: Some of these systems have 50 amp CT to be used on all 50 amp & below circuits, while some have CT’s down to 20 amps.  Are the larger CT’s less accurate on smaller circuits?  Does it matter?

1. Sense: $299 on website; $399 for solar
Con: Reportedly “has a bad time with inverter driven motors” such as I assume the Mitsu has.
Pro: Seems simple plug & play

2. Mini-Monitor, GBA article estimates cost at $1k
Cons: Not plug & play, without wide adoption may become obsolete

3. Energy Curb

4. IotaWatt $179 + Cost of CT – est total under $300
Cons: Per a previous GBA post, limited to 12 channels so you don’t have the option to expand to monitor an entire house, and wifi only/no ethernet
Pro: easy to add solar by just adding a CT, open source, user forum on website

5. OpenEnergyMonitor
Con: Sold overseas.  Per their site using it on a US system seems to add complication.  Definitely not plug & play.
Pros: Seems to be open source.

6. BrulTech GreenEye $399 and up
Con: Seems geared to pros not consumers.
Pro: Seems expandable, has wifi & zigbee

7. Curb $399 and up
Pro: Integrates with smart things & Android (does it have wifi?)

8. Eyedro Eyefi $399 for wifi on their website, but $149 on Amazon…
Con: Connects to their proprietary service, so concerns with them changing to subscription or shutting down
Pro: Seems plug & play

9. Egauge Meter starts at $550 + devices; too expensive

10. Starts at $219 on Amazon

11. Powerwise $935 + devices = too expensive

12. Sensa Phone Sentinel need to email for quote = non transparent

13. TED5000 $169+ $10/ea for 60 amp CT, etc,
TED Pro $299 + $150 for “Spyder” with 8 CT’s (donut solid core not split core, which seems to make this a non-starter…)

14: Emporia Vue $136 for system and 16 50amp CT’s
Con: Looks like CT’s are solid core based on photos but not specified… Measures current thus may not be accurate for inverter motor.
Relies on private commercial website which could be both harvesting data (seems it is per the privacy policy) and subject to future subscription cost…
Pros: CT’s are clamp on.  Lowest total cost system for 16 CT’s
Per correspondence with the company the old Gen 1 version measured current, but the new Gen2 version, available 8/2020, measures voltage and actual usage,

15. Efergy Engage $145 for base kit + $22 per sensor
Con: Measures current;  estimates voltage, thus may not be accurate for inverter motor.
Pro: Affordable for the base kit (might get expensive if you want to monitor everything)

16. Efergy TPM $150 for base kit w 2 CT’s, + $22 per CT (max 5 total)
Con: Monitors max of 5 circuits, seems to be proprietary wifi only
Pro: Measures Power so good for inverter motor, comes with its own display

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  1. cr0ntab | | #1

    I've tried the Sense, IotaWatt and eGauge.

    I sold my eGauge and Sense and I use only IotaWatts now

    They work great and the developer is really awesome about support.

    The IotaWatt is plenty accurate and I'm able to export the data to whatever I want (PVWatts, EmonCMS, InfluxDB)

    I personally use InfluxDB and it works great, have a great view of all my consumption.

  2. this_page_left_blank | | #2

    I have and can endorse the Brultech GEM. The tech support is great. I went with it because it has true monitoring on every channel, and it's standalone. A lot of the monitors out there only really monitor the mains and try to "smartly" identify what appliance is operating. I can see how that might be effective with certain types of appliances, and with only a few running. They're trying to tell me that if my water heater, heat pump, oven, stovetop, dryer and a couple of random plug loads are running simultaneously it's going to figure that out accurately? GTFO is all I have to say to that. I'm also not a fan of being reliant on the internet in general, and a specific web server in order to access my data. A lot of the monitors are like that. The GEM w/ Dashbox is its own local server, so even if the net goes down (as it does here when it so much as rains), I don't lose access to my energy monitor. It does have the option of uploading to a web based server as well.

  3. charlie_sullivan | | #3

    I think the issue with accurately monitoring inverter minisplits will be common to a lot of those. Too many just measure current and guess power. The two already mentioned (Brultech and IotaWatt) do say they measure true power, as does the TED. I've had a TED1000 for more the 15 years and it has worked reliably, but if you are not wanting to pull wires out and thread them through cores I can see why that would be off the table. On the other hand, if you aren't comfortable poking around in your panel, maybe you want an electrician to do it anyway, at which point the lack of a split core for the branch circuit monitors is not a big deal. But I don't have a reason to prefer TED over IotaWatt.

    1. user-5946022 | | #13

      Please clarify - The Iota Watt website states "IoTaWatt measures each circuit using a passive sensor that clips around one of the insulated wires of a circuit to measure the magnetic field created by current passing through the wire."

      This makes it seem like it is measuring the current.

      But then it states: "A wall transformer inserted into an ordinary receptacle provides IoTaWatt with a low-voltage reference from which it determines line voltage and frequency."

      Is this what makes Iota measure power?

      Most importantly: Will Iota be accurate to measure a Mitsubishi Mini Split?

      1. charlie_sullivan | | #17

        Right. It's actually a little more complicated than just the fact that it measures both voltage and current. It's that it uses the actual wavforms of those to calculate actual power, rather than guessing based only on the magnitude of each.

        So I am confident that it does the right thing to measure a minisplit accurately. I can't vouch for whether it's implemented well as I haven't seen direct tests of its accuracy on a challenging load. But maybe they have done that.

  4. _jt | | #4

    Emporia is fine. App based only - not on the web site and easy to install. Between $50-100 based on how many channels. (I think there are 10 channels for $100)

    You can export, but it's much easier to do everything on your phone.

    1. user-5946022 | | #6

      I've added this option to the list above. Looks like 16 channels for $136, so probably the best price. Although the CT's are donut style, the low cost means perhaps it is worth it for an electrician to install. A few questions:
      1. Does this system measure current and guess power, or does it measure true power (for inverter minisplit)?
      2. Is there a subscription associated with this? When you say App based only, not on website, does that mean all your data stays local or that it goes to the cloud and you can only access it on a smart phone app?
      3. Can you link this data to any other smarthome type systems?

      1. _jt | | #10

        They are clamps. It infers current from the magnetic fields. Probably +/- a couple percent on current. Very easy to install, just clamp over wires. On 220v circuits you just clamp 1 and it automatically doubles the reading.

        1. this_page_left_blank | | #11

          Does it measure the voltage? If it doesn't, that's how it ends up being way off on reactive loads. Devices that don't monitor the voltage and the phase angle end up reporting volt-amps, which is different from power (unless it's a purely resistive load, in which case it's the same).

          1. _jt | | #14

            It does seem to measure volts. You just add a multiplier on a two phase circuit.

          2. charlie_sullivan | | #21

            From the Emporia FAQ:

            "Does the Vue monitor voltage?"

            "No, the Vue assumes the system is 120V. You can use the mains and circuit multipliers in the app to adjust for your specific voltage."

            That's no problem for adjusting for 120 V vs. 240 V, or for tweaking for your voltage if it's a little high or low. But it is not measuring true power: it's assuming power factor is 1.

          3. this_page_left_blank | | #23

            This makes sense, based on the price of this unit.

          4. user-5946022 | | #25

            Per correspondence with the company "Our new Gen 2 model measures real power along with measuring current, voltage, and phase. The link you listed is our FAQ's page which is referring to our Gen 1. Previously we were only able to measure current and assume a voltage of 120."

            If this is the case, this system is by far the most affordable of the units that measure true power. The downsides seem to be a) they can sell your data, b) they could start charging for a subscription at any time c) it only works via an app; there is no website, d) the smallest CT's are 50 amps, accurate down to 20w. So if you have LED lights with a draw of less than half of that, and only one light in a circuit is on, it won't register its usage. I think the Iota also only goes down to 50 amp CTs but they don't give the lowest wattage read on the website.

          5. Expert Member
            Akos | | #26

            You can always decrase the range of a CT by looping the wire. A 50A CT with the wire passing twice through the core is now a 25A CT, wrap it 10x and becomes a 5A CT.

            I've done this many time when measure smaller currents, works great.

            An interesting application is to do math with it. For example, running the wires of two loads on the same phase through a CT gives you the sum of those two loads, but if you run one of the wires backwards, it gives you the difference between the loads. For example, you can do this on a battery + solar setup. But subtracting the battery/PV current, you get your building loads without having to put a CT on every breaker.

    2. charlie_sullivan | | #7

      This is, however, an example of one that won't be highly accurate on something like an inverter motor speed control.

      1. bfw577 | | #8

        I have been happy with my $129 Efergy Engage hub. I have my 2 mini splits, my house and solar panels connected. I checked the measurements with a Fluke amp meter and found them to be accurate.

        I attached a snapshot of my mini split monitoring.

        1. user-5946022 | | #12

          Thanks. Added that to the list as #15. Per their website, this one measures current; voltage is estimated. Purportedly this is not as accurate for inverter driven motor of mini splits...

          1. CollieGuy | | #15

            We have an Efergy Engage TPM system that measures current, voltage and phase angle (separate clamps for the the main feed and our two ductless mini-splits). I cross check its readings with that of our utility meter and the results are pretty accurate; typically, they're about one per cent higher than the latter.

          2. charlie_sullivan | | #18

            It's confusing because they have lots of different models. The TPM model that CollieGuy mentions does measure true power (TPM stands for true power monitor) so that should work well, but the others do not. $149 (on sale) but it doesn't look like it can be expanded to more circuits (?). Edit: turns out it does allow more circuits: good news!

          3. bfw577 | | #19

            I found it to be extremely accurate. My measurements match up almost exactly to the listed minimum and maximum wattage of my mini splits. Even if it's off by a few watts seeing the modulation has been a tremendous help in how I run my mini splits. It eye opening how little power these splits use. My Gree can throttle down to 80-100 watts in cooling mode. The listed spec is a COP of 10 at that output.

          4. user-5946022 | | #22

            Added the Efergy TPM to the list. For some reason there is no option to "Reply" to Charlie's post. Per Efergy website the TPM monitors a max of 5 circuits.

  5. jay443 | | #5

    I have IotaWatt and it's absolutely great. Super easy to install the CTs and get it up and running. Seems to be accurate, and as the first poster noted, the developer is very responsive and the customer service has been great.

  6. jberger | | #9

    I've used Ted 1000 & 5000, Blue Line, eGauge in prior homes and have Sense in our current home.
    I cannot recommend the Sense, while the interface is nice, the AI based ID and reporting is incredibly frustrating. Even with the # of appliances defined in the tool, it still goes and "finds" new appliances on a consistent basis. I've given up on it for anything but top level reporting and graphing. Also, less than 1 year old and is constantly disconnects and needs a hard power cycle to come back online.
    The two things Sense does well is integrate with TP-Link KASA plugs and outlets, I have appreciated having those integrated into the sense graphs, and recording data even when it loses network connectivity. If you want to monitor specific branch loads that don't use a standard outlet, Sense isn't a good fit.

    My TED units came with split CT's so installation was very simple, I don't know if something has changed recently, as I've had those installed for years and just pulled them out of the panel before we sold the house.

    eGauge is very good for branch circuit monitoring, but I used it back when you had to basically roll your own graphing and integration solutions. It always gave me the most accurate usage at the expense of a lot of care and feeding of the interface.

    I've been trying to decide between Iotawatt and Brultech myself, so thanks to the folks who posted thier experiences. I'm sold on going back to circuit level monitoring so multi-channel CT support is a must for me.

    1. charlie_sullivan | | #16

      You can add multi channel circuit level monitoring to a TED 5000. The Cats for that are not split core, so you do need to disconnect the branch circuits to thread them through. That's a lot easier and safer than disconnecting the main feed, so it's a reasonable compromise to have split core on those and not on the branches.

    2. skrapple | | #28

      Hello Jayson,
      Sense employee here - just wanted to relay to you that Sense does now support branch circuit monitoring as an alternate use for our solar CTs. You can monitor up to two dedicated circuits, either 120v or 240v. This may help in your situation! It's great for inverter-driven heat pumps, for example. If you give it a try, please let me know how it goes.
      As for your monitor connection issues, that's definitely not expected behavior and I'd be glad to try to help you out. You can send an email to [email protected] and let them know I sent you. We'll do our best to suss out whatever is causing those disconnections.

  7. Expert Member
    Akos | | #20

    Another recommendation for IotaWatt. I have been using one for about three years now. The setup for web monitoring is not the most straight forward (not plug and play by any means), but the local app on the web server is very simple to use.

    I've also had a Ted5000 for a while, it mostly works but the power line communication is not reliable, I had a hard time keeping it going over the years. I did have one of the MTUs fail after 6 years. The software on it is pretty dated but the runs locally and no subscription.

    I would be weary of anything that requires internet connection for operation. Lot of these IOT companies disappear over time and you might end up with hardware that won't work.

  8. AndrisSkulte | | #24

    I'm happy with my IotaWatt too... Going 1 year now, installed it myself when we upgraded to a 200A load center for our four mini splits. It was the best option for what I wanted, and very flexible too...

    Tiny gripes - I wish it was simpler to view remotely (away from my home network) and to sum up costs, but I suppose that's the cost of almost open source software... Wish it had a wired connection and an input to add more channels too to measure each breaker, but that's not a big deal. I've got math channels to get the other details... It would be super cool to identify device signatures to show what devices consume the most power (like the Sense, but actually working). I need to teach myself how to do that...

  9. charlie_sullivan | | #27

    That's good news that the new Emporia does measure voltage and true power.

    Iota can be configured to work with any generic current transformer so you can go buy a 20A CT from someone else and set that up, if the 50 A doesn't give good enough resolution.

  10. skrapple | | #29

    Just wanted to add a note that Sense now supports monitoring of up to two dedicated circuit loads (120v or 240v) as an alternate use for the solar CTs. This is a great solution for any loads which Sense has a hard time with, such as large inverter-driven variable speed motors.
    (full disclosure - I work for Sense!)

  11. _jt | | #30

    Another FYI: There is a third party integration with Emporia and Home Assistant. I can plot inside, outside temperatures and watts used on the mini split, for instance. (I get my temperatures from ecowitt, which also has a 3rd party Home Assistant integration)

    1. user-5946022 | | #32

      @Jay- that is interesting. Do you get your data direct from the local box, or do you have to pull it out of Emporia's cloud and pull it into Home Assistant?

      1. _jt | | #33

        It looks like it's querying the cloud.

  12. tundracycle | | #31

    @CL, thanks for starting this!

    For me it seems the best options are IotaWatt, TED and GEM. All seem to be accurate and will work w/ pretty much any variety of residential loads. None require internet and no concerns about the company going belly up and leaving the equipment useless.

    I think I actually prefer the non-split CT's for TED because they're smaller inside the panel. Ideally perhaps a few of each; non-split for things I want to monitor long-term and split for circuits I may want to move around. Latter s/b possible w/ IotaWatt.

    Now to analyze the output/data/analysis capabilities of these. Thoughts from those w/ experience?

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