I currently have a SMA Sunny Boy 6KW inverter for our solar system which is grid connected. I also have a 125 amp/50amp manual transfer switch to allow my 9KW propane generator to route limited power to the house main breaker panel for when power is out. I first turn off almost all breakers in the main panel except for a mini-split A/C breaker, and a few 110 breakers for the refrigerator/freezer, internet modem, and a lighting circuit. This installation works fine.

I would like to do something to allow use of a separate 110 outlet that the Sunny Boy inverter supports for daylight use of the solar energy and not have to always use the generator when the grid is down. Since this outlet only supports 2200 watts I would like to use it basically when the weather is nice but I want to keep the refrigerator/freezer running. Obviously, an extension cord from this outlet to the refrigerator would work but this involves moving the refrigerator to switch the plug which is not an easy task.

Can anyone suggest a safe way to get power to refrigerator without having to move it each time to sometimes use this capability for limited power from the inverter? Yes, I have a EE degree but I basically only do basic house wiring.

  • Use an inverter which can control the start / stop of the generator
    – Solar Mike
    Apr 8 at 19:39
  • Sunny Boy includes many inverters. Some are grid-tie only, and others have special tricks. We would need to know the model. Also +1 for knowing your limits. Home wiring is a very different world, the EE'ing is done behind the curtain and it's all about conformance with that design. Apr 8 at 21:27
  • What precise model is your inverter? Apr 9 at 2:37

1 Answer 1


Well there's an easy approach: short extension cords. Connect the refrigerator to the wall outlet through two short extension cords; tie or mount the connection between the two cords at a place that's easily reached without moving the refrigerator.

If you prefer a more hard-wired approach there are infinitely many ways to approach it. One is to re-work the mains wiring that feeds the refrigerator outlet, incorporating a DPDT switch and an inlet socket. Connect them so that the DPDT selects between mains power or inlet power; use an extension cord to patch between the inlet socket and the inverter's receptacle. There is lots of flexibility as to how these would be physically arranged. It might be convenient to put the switch near the refrigerator or near the circuit breaker panel; it might be convenient to put the inlet socket near the switch or near the solar inverter. It's up to you.

  • Sunny Boy 6.0-US inverter – Model SB 6.0-1SP-US-40 The 110 outlet is already wired to the inverter about 12 inches away with a standard 110 outlet.
    – Dave
    Apr 9 at 20:14

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