PamCarter1: I want to start small with off grid Chest Freezer

This discussion was created from comments split from: Inverter to run small chest freezer?.


  • PamCarter1PamCarter1 Registered Users, Users Awaiting Email Confirmation Posts: 1
    I want to start small by running a small chest freezer totally on solar. I have ordered 3  200 Watt panels . I was planning on 3 deep cycle batteries. What size inverter will I need,?  I had rather buy larger than too small so I can add to this set up later. Also can you recommend a charge controller or anything else I might need . Thanks for any input in advance !
  • mcgivormcgivor Solar Expert Posts: 2,816 ✭✭✭✭✭
    To properly size a system my suggestion is to log the energy use with a Kill-a-watt type power logger using grid over the course of a week, preferably in the warmest months, this will provide a fairly accurate figure of its demands. From this the amount of PV along with the battery needs can be calculated, geographic location will be a factor in determining what equipment is required. Don't buy anything until a calculation is made, that is a recipe for dissapointment.

    Creating a new thread will be advantageous as all feedback will be directed towards your particular questions.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • BB.BB. Super Moderators, Administrators Posts: 29,006 admin
    Welcome to the forum Pam,

    I have split your post to a new thread--So, as McGivor said, we can discuss your needs and questions specifically.

    The thread you posted in has a lot of the basic information on sizing such a system. To give you some better answers, I would like to ask you some questions...

    Why do you want to have an off grid freezer? To save money? To have emergency backup power (storms)? Getting an RV ready for travel?

    Where will the system be installed? Possibly outside Dallas/Ft Worth Texas?

    Will this be 12 months a year system? Emergency backup (winter/summer/when typical power outages)?

    It is pretty difficult to start small and upsize a system later. The loads define the battery bank size, and the loads+battery bank size drives the size of the solar array (more loads, more solar, poor sun/shade/etc. more panels, larger battery bank, more panels)....

    If you size the system large enough for a freezer (where you need more than enough harvested energy to keep the Freezer running 100% of the time (i.e., after a few bad weather days, or very hot weather/dropping in new food to freeze--You don't want the system to be shut down for a couple of days for the batteries to recover). This usually means that a bit larger system, and you can run some LED lighting, small laptop, cell phone charger (for Internet), and run a 12 volt RV Water pump. And during bad weather, you just cut back on the optional power usage to keep enough power for the freezer.

    Besides simply using power 24x7 (typically 1,000 to 2,000 WH per day), standard compressor refrigerators/freezer motors have a very high starting current requirement--Which means as larger AC inverter (1,200-1,500 Watt minimum) and larger battery bank. And this also gives you some extra Watts to run the optional loads.

    There are newer "Inverter Compressor" fridges (and freezers?) that are becoming available now... They use about the same amount of energy (Watt*Hours per day), but have much lower starting current (you may be able to run a 300 or 600 Watt inverter and smaller AH battery bank). I have not seen inverter-compressor freezers in small capacity freezers in the USA yet (more common outside USA), but with a little looking around you may find some (I am not in the solar/appliance business--So I don't have direct knowledge of the market).

    Once you have a good idea of your electrical needs--Then you can start penciling in equipment. I highly suggest that you do not purchase anything solar until you have done the paper designs. It sometimes can be difficult to mix the "un-designed" equipment into a single system.

    I just did a quick search on HomeDepot and they list a (not cheap) $1,100 6 cuft upright 12/24 VDC freezer that pulls 532 Watt*Hours per day (1/2 or 1/4 typical freezers).>++st:{inverter+compressor+freezer}:st+cnn:{0:0}+cnb:{0:0}+oos:{0:1}+pt:{freezer}:pt+rt:{inverter+compressor}:rt+dln:{564660}+qu:{inverter+compressor+freezer}:qu

    It would make a sweet DC solar power system... And being an upright unit, you don't have the issues of having to dig through a chest freezer and moving baskets around to find the food.

    It is a manual defrost--Which can be a pain.

    If you do stick with an AC freezer, here is the Kill-a-Watt type meter where you can measure your actual energy needs:

    Depending on your present and future needs--If it just a solar freezer + some other small loads (LED lights, cell phone charger, Tablet computer charger, RV water pump)--I would look very hard at DC freezers (like the HomeDepot one).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 1,266 ✭✭✭✭
    Also consider the Sunstar DC chest freezers.    I'd get 4 batteries and go 24V.   Perhaps with a Midnite Solar Kid charge controller.

    I am available for custom hardware/firmware development

  • WaterWheelWaterWheel Registered Users Posts: 320 ✭✭✭
    edited December 2018 #6
    My 1st solar system was designed to run my inefficient 5 cu/ft chest freezer (kept in the car port) that was rated at .8 kwhs/day.      Living in N. GA so the freezer used a lot of power during the long sunny hot days and less power in the winter.

    200 watts of Renegy panels (from Amazon) Tristar 45A MPPT controller, 1000 watt PSW inverter, and three 106 amp/hr marine batteries from Autozone.      It worked 98% of the time but a few times (over several years) not quite enough power to get the batteries charged enough a few times on cloudy hot days.      I needed a bit more panels which you seem to already have.

    I didn't know enough to do the basic math to keep the batteries fully charged so they only lasted 2 1/2 years but the rest of the system still works after 8 years (I added more panels and better batteries).

    As more knowledgeable people here have suggested find out how much power your freezer needs.       I now have a 2nd freezer that's twice the size of the 1st one and uses less electricity (rated at .7 kwh/day for a 10 cu/ft freezer so twice as efficient).

    Learn battery maintance, something I barely did with that 1st solar system.      While there are many great batteries out there I upgraded to Trojan T-1225 125 amp hour 12v batteries for the replacement set of batteries.      Found them at a local golf cart store and they are still going fine after 5 years.

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

  • NANOcontrolNANOcontrol Registered Users Posts: 122 ✭✭✭
    I use a 2KW inverter on my 7CF chest fridge. Anything less will likely not work on a standard AC compressor. As this is a light load except for starting, I remove the fans to reduce current draw.  I only use a car battery as I store cold in the day and don't run at night. This would also work for a freezer that can be brought very low in temperature. I go with more panels so it can work even on less than prime days. The control is a little more complex as it monitors battery voltage.  As long as the battery is above a certain level, the freezer should work as much as it can. Freezers can go several days without running if not opened much. That is my uncommon take on solving the problem.
  • jonrjonr Solar Expert Posts: 1,266 ✭✭✭✭
    edited December 2018 #8
    +1 on allowing a little bit of freezer/fridge temperature variation to shift power drain to sunlight hours (saving battery wear).     IMO, the ideal way to do this is two thermostats, with the availability of sun causing a switch between them.   

    Less perfect is a timer that turns it off for some number of hours before expected sunlight.  Be careful, in hot weather, many freezers won't have the excess compressor capacity to "catch up" in 8 hours.

    Any turn-off plan might  also turn off the inverter for additional savings.

    Gluing more foam to the freezer makes sense if you can tolerate the look (and the walls aren't used as a condenser).

    Get an inverter with good surge capability and low losses.  1000W works for me.

    I am available for custom hardware/firmware development

  • wild01wild01 Solar Expert Posts: 97 ✭✭✭
    edited January 22 #9
    if you are looking to start small and build up I would start with one of these and 4 l16 batteries. I have 2 mppsolar inverters and have been very impressed by them. for the price they can't be beat. these come with an 80 amp mppt charge controller built in and cost about what you would pay for just a charge controller. they ship them dhl strait from Taiwan and both mine got to me in 3 days. They are on ebay and amazon. Be aware they are not ul listed so if you need to be code compliant in this install they won't work. These can be stacked in split phase in the future so you can have 240v if you ever need it, but one would be capable of pushing an efficiently run house.

    they are on amazon and ebay. I've bought one of their inverters of of each and there was no difference in service. The shipping speed blew my mind, both of them where in the usa and through customs in 24 hours but they did hand off to usps for final delivery. (it took usps longer to go the last 200 miles than it did for dhl to get it from Taiwan to Denver. oh and dhl's tracking number stops showing updates after the handoff, but if you call they can still track it)

Sign In or Register to comment.