Check my math please...

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FLguy
FLguy Member Posts: 1

I'm looking at a way to power my condo during downtimes, such as events like Hurricane Ian we just went through here in SW Florida. See if I am correct on this please:

Refrigerator: 115 v x 2.1 amps = 356.5 watts. To run for 24h would be 356.5 x 24 = 8556 watt-hours. Seems like this exceeds the capacity of your electrical storage units.

Also, am I correct that three, 200 watt solar panels = 600 watts, so 10 hours of recharging under optimal conditions = 6000 watt-hours?

Thank you for any advice you can give.😎

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  • JPP
    JPP Member Posts: 1 ✭✭
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    Can't help on the math, but I'm sure someone will...but I am looking at generators and found this article in Popular Mechanics (they are a trusted site been around forever). They say the Yeti 1500x can power a full sized refrigerator for 28 hours. Here's the link https://www.popularmechanics.com/adventure/outdoors/g37295464/best-solar-powered-generators/ That's without additional batteries. Not sure about the solar panels tho..


    Good luck...

  • Sarah
    Sarah Member Posts: 3 ✭✭
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    Those fridge watts are at peak, I believe. The compressor doesn’t typically run all the time. Usually about 1/3 of the time from my reading. The more you open and close it the more often it will kick off and on tho

  • jg164
    jg164 Administrator, Moderator Posts: 313 admin
    edited August 2023
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    The best way to get run times for your conditions is to measure them because they vary so wildly from place to place and fridge to fridge even for the same brand and how often you open the door.

    If you have not yet purchased a Yeti, spend $20-$40 and measure the actual power consumption for the situation you are planning for with a watt meter or smart plug. Then write down the Watt Hours used for the planned duration. To be even more precise, actually run the fridge off the yeti and be present to switch the fridge back to wall power when the Yeti runs out of power. All other calulations and estimates may help for purchase planning but I would do real power out testing to gain confidence in what I can actually rely on.

    Here is what I mean

    I found the US DOE page that stores all the Yellow "Energy Guide" values. There are currently 4,081,562 appliances listed as of right now! You can search for appliances by model and convert the annual Kilowatt hours to just instantaneous watts.

    1. 645 KiloWattHours/Year
    2. times by 1000 = WattHours/year
    3. divide by 8760 hours per year = Watts = 76.63

    Here is the Residential Refrigerator and freezer section CCMS - Public Database (doe.gov)

    Each Goal Zero product page shows some runtime and recharge estimates in a section down the page called "What can the yeti power?"

    Here are the Full Size Refrigerator numbers for the big 3 Yetis when I checked today:

    Those run times might be assuming very ideal conditions like these:

    • The fridge is running like new.
    • The cord between the Fridge and the Yeti is short, securely connected and is of a large enough gauge that the voltage drop is low.
    • The fridge contents were already cooled to its set temperatures before starting on Yeti power.
    • The fridge is not opened at all for that duration.
    • The room is cool enough that the fridge does not have to work extra hard.
    • The fridge is able to maintain its set temperatures at an average of 71W.
    • The Yeti is not powering anything else, is running like new and does not need to run its fans too cool itself.
    • The Yeti inverter power loss for converting DC battery power to AC power is really low.
    • The Yeti is set to use the full capacity in performance mode 0-100%

    As soon as those conditions change, the run times will change.

  • jg164
    jg164 Administrator, Moderator Posts: 313 admin
    edited August 2023
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    Here is an example of a watt log overtime for a house fridge that was started from room temperature. Notice the larger power draw on the left as the fridge works to cool to set temps and then only turns the compressor on every now and then to maintain temp. Some fridges will also turn on a defrosting heating element periodically which surges at ~200W for 10 minutes and then the fridge has to do extra cooling to get back to set temps. This log is for a 28cu.ft fridge with no running ice maker.