GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

All electric dwelling using too much electricity?

wanmi | Posted in Energy Efficiency and Durability on

Not sure what kind of answer I’m expecting, any insights will be helpful. I have a 500 SF apartment over a garage in upper lower MI, zone 6, used as a cabin. No gas at all, all electric. Well insulated all around, didn’t have blower door test but likely to blow under 2-2.5.  Heat and cool with Fujitsu Halcyon mini split, single outdoor unit and 2 heads. Full kitchen and bath, fridge in apartment and another in unheated garage. Electric water heater. 

Even when we are not there, mini split and 40 gal water heater turned off,  we are using 20-28 kw per day. It seems insane, 1$00/month for a vacant tiny property. No lights on, no water heater on, no heat on. By the way, the kilowatt usage, when we are there, barely changes from when we are not there. Some days it will drop down to below 10 when we are not there, totally out of the blue. Our electric bill is as much as our 2000SF home we actually live in. I asked the electric company if they can do an audit on the home and they said they don’t provide that service.  

We are building a full-size home up there in the next year or two and we were considering going all electric. This has us really questioning that idea.

Any observations? 

Much obliged. 

jim 

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. canada_deck | | #1

    Yeah that's messed up.
    To be clear, you are saying that you use 20kWh or more when the mini-split and hot water heater are off?
    For reference, I will use about 1.5kWh/day in a larger apartment when I am not home and the only electrical load is one full size fridge and some small plug loads.

    What is a complete list of items that could be drawing power?
    Do you have any external lights?
    Do you have any other heat (baseboards?)
    Plug loads (computer, TV, etc.)
    Continuous ventilation (ERV, exhaust fan)?

    *Edit to add: Define "off" for your hot water tank and mini-split. Are they fully de-energized (at the breaker) or do you just turn down the set point?

    1. wanmi | | #7

      Water heater turned off at the breaker, mini split power off with the remote control.

      We have 2 refrigerators, lights from plugged in electric stove, one nightlight in the bathroom plugged in. We have electric baseboard resistant heater in a 6 x 8 mechanical room, heavily insulated, has been turned off for three weeks.
      Router and modem for wifi, no other lights turned in indoors or out.

  2. Expert Member
    Akos | | #2

    "500 SF apartment"

    "Fujitsu Halcyon mini split, single outdoor unit and 2 heads"

    Well there is your problem. Tiny space with a WAY oversized multi split. These can be made to work but they need to be right sized otherwise you might not get much above COP1. Add in there the all too common install issue and possibly low refrigerant and the place could be an energy pig.

    Unfortunately the ship has sailed on getting this right but if you are looking at a new house, try to avoid multi splits. If you do go down the multisplit road make sure it and all the zones are sized for actual building loads.

    I'm heating a similar sized cabin in zone 6 with a single wall mount mini split and using around 5-10kWh/day keep the place at 50F.

    1. canada_deck | | #3

      Yeah but he is using 20-28kWh per day when the mini-split is off.
      Actually... good clarifying question here. Is the mini-split actually fully off (breaker is off) or do you just turn down the t-stat. Perhaps this missing load is the base pan heater?

      1. user-5946022 | | #4

        Yep, canda_deck has asked the question to answer. Next time you leave it, turn the mini split breaker totally off.

        Also check to see if you have a smart meter or an old fashioned one with a spinning wheel. If the old fashioned kind, I would start troubleshooting with that - make sure the wheel is spinning. Then turn your main breaker to your unit off and make sure the wheel stops spinning. If it does not stop spinning, you have a some other load connected to your meter. Since you wrote this is an apartment, rouge loads are not unheard of in multi unit situations. Just one wrong assumption by someone who does not care or is not paying attention or is rushed and you have some other load connected. If it does stop spinning you know that the load comes from your own apartment. Turn all your breakers off. Turn them on one at a time, starting with those you think should have ZERO load - lights that are off, etc. One of the breakers is likely to start that dial spinning and you can figure out what is connected to that circuit.

        Another way to do this is to get a device like Emporia Vue, but many people need an electrician to install that. That is a slick solution and would work if your electrical meter is digital.

        Another option with either a digital or analog meter is get a Kil a Watt - a $20 device that measures load. You plug it into the wall and plug any load you have into that.

        There is no way a 500 sf apartment with its HVAC and water heater off should use >20kw day. A house more than 4x that, with water heater and HVAC on uses 8kw day...

        1. wanmi | | #8

          Thank you for the thoughtful reply. Let me clarify, we call it an apartment, but it is an individual structure above our own garage on our own property. I will shut down mini split at the breaker and see usage for a couple days. Then I will power off the main to see if the meter is still turning.

    2. wanmi | | #10

      Why avoid mini splits? You’re using one, yes? What would be the suggested alternative? It’s still early enough to plan. Thank you.

      1. paul_wiedefeld | | #13

        Use ductwork - the mini split in every bedroom route is to be avoided at all costs. It’ll be loud, oversized, inefficient, moldy, and have awful filtration.

        Note: by “mini split”, I mean how the term is usually used - a ductless unit serving one room. They make so many flavors of minisplits now that the term should be avoided. Ducted vs ductless and one outdoor unit to one indoor unit vs. one outdoor unit to many indoor units are the real differences here.

        1. wanmi | | #15

          Ok, that makes sense. The wall unit is what you are calling the mini split. Air-source heat pumps as a technology should be consideration still, correct? Ducts would also be good for an Erv and whole-house humidification. The barnpartment has a relative humidity in the 20s if the heat is on.

          1. maine_tyler | | #18

            wanmi,

            I think Akos' main point was the *multi* split part. I.e. when there is more than 1 indoor unit per outdoor unit. They're a bit of a different animal. Lots of info here on GBA about their potential downfalls.

            I assume Paul comes from a place where ducting is the gold standard and there are probably installers able to perform the work. That's not realistic in certain geographic regions (like mine) due to lack of workforce trained and willing to install ducted minis. It's may also be entirely unnecessary in a 500 sq ft. space depending on how open it is. Ductless mini splits are still a viable and highly efficient option, and is really the only option (more or less) around here. The key is right sizing, and 1:1 mini splits are more forgiving than *multi* heads paired with one outdoor compressor.

          2. paul_wiedefeld | | #27

            Exactly - ducted, air source heat pump is the way to go, especially for a planned new home. Another bonus is how easy it is to incorporate a backup heat source too.

      2. Expert Member
        Akos | | #21

        For a house you want a ducted unit. These can be slim ducted unit or a multi position air handler. You can even use a number of these to zone the house but that does add cost.

        In zone 6 you need a hyper heat outdoor unit, this generally means overseas brands although some domestic brands now offer rebaged hyper heat units (ie Carrier/Midea and Trane/Mitsubishi).

        Even with ducted unit you need to get the sizing right so make sure the heat loss calculations are done properly preferably not by your installer. Generally a good check is if the equipment size magically comes out to say 500sqft/ton or 750sqft/ton, means the sizing wasn't done properly.

  3. maine_tyler | | #5

    In your post you say heat pump is off, but the utility data shows a pretty clear (visually speaking) correlation between outdoor temp and energy use, which to me implies it's your heating system. Or are those graphs not from the relevant time frame?

    1. wanmi | | #9

      Yes, I saw that. But there is not much heat being generated for sure. I’ve been in the apartment when it is zero outside when we arrive and it is sitting at 55. Still, hard to deny the correlation.

    2. wanmi | | #22

      Re multi heads and one compressor, i have definitely experienced some quirks. First, the unit doesn’t always respond well to calls for heat. Also, cannot have heat in one room and cool in another. The apartment has a closed bedroom, closed bathroom and open living dining kitchen guest sofa sleep area. We thought we needed the extra indoor unit for the bedroom with the door closed. Next time I would do main room head and move conditioned air with a floor fan.

  4. greenright | | #6

    Get an Emporia Vue and figure out what is what. Nobody here can tell you what is your energy hog, just that you most likely have one.

    1. pnw_guy | | #24

      I was coming here to say this. OP -- get an Emporia Vue 2 -- it will tell you your total usage and your usage on every circuit. This will quickly and decisively identify your problem.

  5. artisanfarms | | #11

    Check each circuit with an ammeter to see where the draw is. You likely have something partially shorted somewhere that is generating a fair amount of heat (and using a lot of power to do it). We had something similar happen in the shop a few years ago. A loader bucket on a tractor partially crushed an extension cord and turned the bucket into a space heater. We discovered it after getting a larger than expected electric bill.

    1. maine_tyler | | #12

      also add to the list an IR camera to check for hot breakers.

  6. paul_wiedefeld | | #14

    Looks like from 4/19 to 4/22 the issue was solved. Wonder what changed!

    1. wanmi | | #16

      Yes, the temp vs energy use graph is telling. So maybe the question should be: my heat source, heat pump system, single unit, double head, is using a ton of energy. Even when we are not in the place, which is most of the time, and the unit is turned off with the remote control or set to its lowest temp (55? 60? And it doesn’t seem to matter if off or set to lowest temp, kw use is very similar).

      Why would this efficient system use so much energy? Is there something obvious I should check?

      Thanks again, I really appreciate all the responses.

      Jim

      1. maine_tyler | | #19

        Do they have backup resistance heaters? There was a recent post here where that was the problem.

        It can be difficult to diagnose mini split consumption issues via online forum unless lots of information is shared. The energy monitor everyone is suggesting would help collect more data. You could also find a local tech to take a look.

        1. wanmi | | #23

          I plan on purchasing one of the monitors suggested. The resistance heating has been turned to off also and didn’t change consumption. But, that’s at the unit and not the breaker, which I will do next.

      2. paul_wiedefeld | | #26

        The most recent week doesn’t show the temperature impact as much - the 19th was cold and usage was low!

  7. nynick | | #17

    Shut your breakers off one at a time and track the meter and usage. The culprit should show up in a hurry.

  8. Expert Member
    Akos | | #20

    If your mini split is off and you are still running at 20kWh/day than there is a space heater somewhere running. Doesn't take much to chew up a lot of power with a space heater.

    Could be your utility room needs more heat than you think, you can get one of these plug in watt meters for the heater and check.

    Running multi splits at 50F or 60F would definitely use a fair bit of energy. Multi splits are quite terrible providing just a little bit of heat, so that case they would be short cycling a lot so COP would be not far off from a resistance space heater.

    As for power use when off, most heat pumps have a crankcase heater. This is somewhere around 30W to 60W, does add up but not a whole lot. Some heat pump manufactures do a terrible job of base pan heater control and in some cases it is turned on any time bellow freezing. These are in the range of 100W to 140W still not enough to account for 1kW baseload you are seeing.

    As other said, the best way is a whole house power meter. These are pretty cheap nowadays.

  9. pnw_guy | | #25

    OP, as another poster commented, get an Emporia Vue 2 with the 16 individual circuit clamps. It will quickly and decisively identify your problem.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |