Electric Usage Chart

Discussion in 'Maintenance and Troubleshooting' started by PAPete, Jan 1, 2011.

  1. PAPete

    PAPete New Member

    As an FYI - Attached is a chart I created in Excel of the ratio of daily kwh usage (from electric company) to daily heating degree days (from www.degreedays.net). My system did not seem to be running properly and the electric bills were very high. Communicating this data to the installer eliminated the 'cost of electricity' issue and allowed me to focus solely on electric usage. Because the house is not occupied, almost no other electric is being used, so this data primarily represents just heat pump electrical usage.

    Recently, the system was fixed after it was determined that the compressor had been on lockout for an extended period of time and was running only on auxiliary heat.

    I will continue to update this chart to determine if the fix made a positive impact on electric usage. Sorry the image isn't too clear.

    Attached Files:

  2. MefromMichigan

    MefromMichigan New Member

    Let us know how your electric use has improved (as I am having a similar issue using 150kw a day). thanks!
  3. MikeBaxter

    MikeBaxter New Member

    Electrical Usage

    I've had my Geothermal in for a year now, and for the second winter in a row am seeing upwards of 150KWH per day usage in the heating months. Our system is very efficient in the cooling months. I have attached a chart of our usage since installation.

    Something is definately wrong in my book...

    Attached Files:

  4. PAPete

    PAPete New Member

    Before providing an update, I wanted to wait a couple weeks to see if the last 'fix' worked. It appears to have. My Kwh usage has dropped considerably from highs of 170+ and an average of about 150 per day to an average of 45 - 50 per day. Keep in mind that the house is unoccupied so the kwh usage is primarily for the geo heat pump system. Rarely are lights in use and there are no appliances installed. My electric rate is about $.10/kwh so my cost has dropped from about $15 to $5 per day.

    There have been two repairs so far. First, the system needed to be recharged. When that was done, a short was introduced causing the thermostat to malfunction. That was unrecognized and left unaddressed for many weeks. That caused the resistance / strip heat to run continuously. Second, the short was corrected and the system began to work properly.

    I have limited knowledge to be able to comment if 150 kwh is acceptable for a situation, but based on the original 'geodesigner' system analysis that was done I could tell something was definitely wrong as it estimated about 9,500 annual kwh for heating. At 150 kwh per day the 9,500 kwh would be consumed in 63 days / 2 months. As someone pointed on another post of mine (Another unhappy high electric use victim), based on my system specs, if the loop system ran 24 hrs per day my total usage should be 96 kwh. So, 150 a day was a bad sign.

    As a point of reference, the house size with unfinished basement is 4,349 sq ft - unfinished basement is 1,655 sq ft; 1st floor is 1,655 sq ft; and 2nd floor is 1,040 sq ft. The thermostat is set at 70 on the first floor, with duct work to 1st and 2nd floors and minimal duct work in basement. The temperatures that are being maintained: basement about 60 deg, first floor 70 deg, and second floor about 66 - 68 deg.

    I believe it is important to consider external conditions so I have been tracking the kwh usage in relation to heating degree days (HDD). When the system was malfunctioning the usage was 3 or 4 kwh per HDD. It is now closer to 1. The outside temperatures have been fairly consistent for the past two months. I've attached a few charts illustrating the electric usage a variety of different ways. They all show that over the last couple weeks the electric usage has dropped dramatically.

    Attached Files:

  5. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Feel free to call me, as I may be able to help. I could not open the AEP file.

  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Give my voice back, I lost it in PA on the trip from DC to Cleveland.

    At last it sounds like you might be getting the bugs out of the system. Feel free to give me a call if this is not resolved.

  7. newgeohp

    newgeohp New Member

    I'm glad you got it working

    I like your first graph KWH per HDD deg.
    You can see you were using about 3.7 KWH per deg when you were using strip heat only. Now you are using 1.2 with compressor and maybe some strip heat.
    That would be at least a COP of 3 and maybe better depending on if you are using any strip heat now.
  8. PAPete

    PAPete New Member

    Because I am rarely at the house I do not know if the heat strip is being used. But, the few times I've been there for any length of time the system only ran about 15 minutes so I assume the strip is not being used (much).

    Now that I feel the system is working okay, I dropped the set point to 60 degrees today to save money.

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