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How much power do Enphase and other solar micro inverters draw at night time when switched off? It's actually a very interesting question involving real and apparent/reactive power, the system topology, and whether your storage battery is on-grid or off-grid, and also its efficiency curve.
Let's measure it, do some calculations, and look at when it might be a problem. Buckle up Dorothy!
I'm upgrading my solar power system AGAIN:
Microinvreter panel sizing:
New Enphase system install:
00:00 - How much standby power does the Enphase micro inverter take?
04:53 - Solar Analytics power measurement at night
07:49 - The actual real power consumption of the Enphase inverter is...
08:32 - So why is it drawing 1.1A at night time?
09:20 - Reactive and Apparent power
10:10 - The Power Factor
11:41 - You only pay for REAL power
15:27 - Power Factor Correction & Energy Saver SCAMS
17:29 - DaveCAD: How does the Enphase Microinverter work?
23:38 - Bidirectional energy flow and untility VAR control
27:55 - How many microinverters can you have?
29:02 - What if you have grid connected battery storage?
30:46 - Battery inverter switching losses
33:19 - I2R copper losses
35:29 - Why not disconnect with a relay?
39:20 - Conclusion

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29 thoughts on “Eevblog 1487 – do solar micro inverters take power at night?”
  1. Avataaar/Circle Created with python_avatars bascomnextion says:

    There are people who get charged for power factor and these would be large users so the micro inverters may not be so good for them.

  2. Avataaar/Circle Created with python_avatars Markus Hahnenkamm says:

    Hasn't the enphase gateway the ability to disconnect the micro inverters from the grid. Thus we have relays wich are continuously powered and consume energy and we should have the ability to disconnect the non producing inverters. So a software upgrade which disables the relays over night and with this turns off the inverters and on time turns them on could save some watts real power at least

    6W *6h *365Days = 13kWh ok, some Euros/year, but avoidable

    OK, your last video minute destroyed my comment

  3. Avataaar/Circle Created with python_avatars Jan Bottorff says:

    Hi Dave, could you do a video on how solar inverters interact with the common split-phase 120V/120V here in the US.

    The Enphase inverters only put out 240V, not 120V. If the loads in my house are not perfectly balanced between the phases, I'm puzzled how exactly this works. I assume the 240V is exported through the meter and the street transformers, due to the center tap, can send the same energy back as 120V? If 1 A was flowing across the 240V lines (240W), and my load was drawing 2A at 120V (still 240W) on one leg, what does the flow look like to the meter?

    There is significant legislature debate here in California (and other places) to change the net metering plans such that the energy you export is not nearly as valuable as the energy you import, so it might be nothing like "net" metering anymore. The power companies are arguing why should they pay you $0.35/KWN for power to the grid when they can buy power wholesale for $0.06/KWH. They leave out the detail that the KWH from their wholesale generator 100 miles away going to my neighbor's home has much higher transmission costs than the KWH from my my solar panels going 100 feet to my neighbors home.

    In one proposal, you get credit at the wholesale rate for power you export, like $0.06/KWH, but pay $0.35/KWN for power you import. Load smoothing batteries could help a lot for a day or two, but don't at all help if I want excess energy exports in the summer to build up a net balance in an account to run a heat pump in the winter.

    If this much worse net metering becomes reality, I don't want to get paid $0.06KWH for the power I send to the street transformer to be turned into 120V, only to buy it back for $0.35KWH. I read there are potentially devices that could do the split-phase conversion on my side of the meter.


  4. Avataaar/Circle Created with python_avatars Worf says:

    Non-residential users are charged on power factor, not apparent power. Apparent power as you noted is made up of real power (what you pay for) and imaginary power (which averages to zero over an AC cycle), but as you said, imaginary power leads to real currents. That's what non-residential users pay for if they fail to keep their power factor in check. It's not hard to do either – they just have a big box of capacitors at the power input to the building, usually switchable in and out to keep the power factor in check.

    Also, almost all loads are primarily inductive – motors are everywhere used to drive the compressors of your fridge and air conditioner, motors driving fans that keep you cool, etc. In the past, residential uses of power were mostly resistive – heating coils used in appliances like ovens and stoves and heaters, lights, etc. But these days it's gone inductive as people buy fridges and air conditioners and fans. That's why power companies never need to correct for too much capacitance on the line – there is almost never enough capacitance – so there will be bit capacitor banks at substations (they call them "reactors"), and there will be capacitor banks along power lines as well, and of course, non-residential customers will have banks of them switched in and out because almost all industrial machinery is inductive – driving motors and such.

  5. Avataaar/Circle Created with python_avatars Nerijus R. says:

    Not much smart people like you, dont warry if you dont get millions views… just smart people like you too little… :))

  6. Avataaar/Circle Created with python_avatars Joop Terwijn says:

    Dave, does the sunnyboy has standby power? And I wonder if you could measure the production current and voltage (power) before the conversion on a panel. And then also the output power on AC side. Give you (and us) a view in power used by the converter in production mode.

  7. Avataaar/Circle Created with python_avatars Jody VE5SAR says:

    This video is much more accurate than the first go… thanks for re-doing it. I've got 36 IQ7+, and your first vid had me seriously considering a contactor disconnect.

  8. Avataaar/Circle Created with python_avatars Okurka says:

    You're teasing us. Nobody has two fridges.

  9. Avataaar/Circle Created with python_avatars ILove Scotch says:

    Could you place a large enough Inductor/transformer on the inverter output could you balance it out?

  10. Avataaar/Circle Created with python_avatars Charandeep Singh says:

    I think this calls for a teardown (please buy a cheap [not working unit] from ebay or something)… even if it is potted. 😉

  11. Avataaar/Circle Created with python_avatars tsmwebb says:

    I wonder if the relays disconnect from the grid in a power out?

  12. Avataaar/Circle Created with python_avatars S Schmachtel says:

    I think the typical wiring resistance is only 1 Ohm all the way down to the transformer. So with 1 A say half of the resistance is after the meter, about 0.5W standby losses for a fairly big system, right?
    I guess this is still less than a common stand by device if you consider there is a lot of inverters there.
    And if they do updates why not let it sit there given that your relay switching the whole inverter branch is going to be pretty expensive as well. plus the installation cost for the electrician you'd have to order to install it.
    Well even if you are producing electricity these capacitor currents will occur I reckon, though maybe mostly supplied by the inverter in operation….
    Not too sure what I should think about this. This seems to be a perfect half truth "inverters are eating your solar produced energy" which is not really meaningfully relevant or expensive to overcome. Whereas nobody would care if there are any capacitors whatsoever on your TV or your mobile charger dangling free off the wall socket. They have such stuff, too; in one form or the other.

  13. Avataaar/Circle Created with python_avatars Clem Taylor says:

    The newer IQ8H does list night time power consumption as 60mW, which seems reasonable.

  14. Avataaar/Circle Created with python_avatars ipullstuffapart says:

    Enphase related, Dave I wonder if you have heard about Enphase breaking local API access on the latest envoy firmwares. I've firewalled my Envoy away from the internet now so it can't update or reach enphase servers.

  15. Avataaar/Circle Created with python_avatars IanScottJohnston says:

    With the cost of electricity doubling (and more come October) here in the UK I am looking at battery systems (again!) and Dave's idea of fridges/freezers etc only has me thinking!……and not to mention also measuring the standby power on my Bosch solar inverter itself etc. Hmmmm!

  16. Avataaar/Circle Created with python_avatars CubaPete101 says:

    Why not measure the current draw at night from all points in the system? At the batteries, before the switcher, after the switcher, etc. so we can separate the real power, effective, imaginary? You almost convinced some people to buy some PFC banks there when you started chatting about saving the grid’s energy, but not yours. Do you pay for negative PF in Australia? Anyhow, where is your metering done on your diagram? Are you not allowed to relay the grid off right after the meter, or is that about where your X was?

  17. Avataaar/Circle Created with python_avatars Mr. greens boat tanks and aluminium welding says:

    Can you put in a second inverter but plug it in the power point? Or straight into the power box?

  18. Avataaar/Circle Created with python_avatars mohinder kaur says:

    They can also deliver power to Joe Bydens butt so that it can power windmills!

  19. Avataaar/Circle Created with python_avatars Private says:

    OMG! If you live in communism QLD they force you to have crazy meters that charge you money for the power factor!

  20. Avataaar/Circle Created with python_avatars Junker Zn says:

    Seems like everyone wants to get into the battery game. There is even a standard for off-grid and grid-disconnect situations to allow battery inverters to tell micro-inverters and grid-tie inverters to reduce the amount of power they send to the micro-grid/home-grid. The battery inverter shifts the frequency up from 60hz to 62hz or so (something like that) to regulate the amount of power the solar inverters inject onto the line.

    Without that the solar inverters would push the voltage all the way up to their maximum (typically 130VAC or 140VAC in the U.S.) and then probably either shut-down or start hicup'ing (turning completely off, then on again), when what you really want instead is regulated load-support for whatever is running in the home plus whatever the battery system can take (if anything). And because the standard is fairly new, various inverters either don't implement it or implement it with different frequency ranges and various brands tolerate different voltage limits before they trip-off. So it's a bit of a mess right now.


  21. Avataaar/Circle Created with python_avatars Beauregarde St. Beauregarde says:

    Where's the uncut version of this video? 🙄

  22. Avataaar/Circle Created with python_avatars Kool Aid says:

    Awesome video Dave! Have you done any reviews of different systems. Have been thinking about get a solar system!

  23. Avataaar/Circle Created with python_avatars Robert Peters says:

    What happens as failures occur?

  24. Avataaar/Circle Created with python_avatars Rodrigo Maero says:

    You may not pay for apparent power, but tecnically you'll pay for the cable loss of the current running through the cables in you house so that VAr if too big might take some real W with it

  25. Avataaar/Circle Created with python_avatars Topher Teardowns says:

    Dave Jones, flying spaghetti monster amongst mere mortals. Science bless you 🙌

  26. Avataaar/Circle Created with python_avatars Paul Turner says:

    From my research Enphase is the way to go. But what do I know 🎈

  27. Avataaar/Circle Created with python_avatars massriver says:

    😳Amazing fitting 60hz 200va transformer in little enclosure. Not consume pwr just hanging there. Teardown

  28. Avataaar/Circle Created with python_avatars TheMobilefidelity says:

    I have Chinese micro inverters on my roof, Deye brand.
    They seem to shut down entirely when panel voltage drops below a certain level. I can't even access their management interface at night.

    I suspect the microcontroller that provides the Wi-Fi connection is fed from the DC bus, as the management interface is still accessible when I disconnect the circuit breakers that connect to the inverter.

  29. Avataaar/Circle Created with python_avatars stdorn says:

    I also had my system set to top off a battery bank before switching on the enphase system. I installed a DC distribution system that ran, Co detector, alarm clock, wifi router, cable modem, network hub, cell phone, laptop, ecig, and basically everything with a DC wall wort. In the event of power outage 600ah battery could power an inverter run some of my more important electronics.

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