I'm also playing off grid, and it's been hit and miss. I bought the fridge and stove that came with the Cottage Living pack (I don't have EL). For the most part, as long as I have the ingredients, I can make the dishes in the off-grid, canning, and animal treat categories without any issue. I once tried a dish from City Living. My sim was able to do the prep part, but can't seem to finish cooking the dish on the stove.
Once in a while I'd also get the message that there is no power off-grid, and nearly all the cooking options are grayed out, but then it comes back again. I haven't figured out yet how the power works and how to get a surplus. Auto lights are also hit and miss. One time I was able to select auto lights, another time I couldn't. Without EL I don't really know how to get a surplus of power? Is it just a matter of waiting it out? The only things I'm aware of that uses power on the lot are the fridge, stove, maybe the lights/candles.
So far I've only gotten a message for using up all the water, but that is easily fixed by getting water from the fishing spot. Also, I think I've gotten a pop up that gives an option to turn off utilities, but I thought I'd keep it for a bit more of a challenge. For a small house on an off grid lot, with only a stove, a fridge and small bathroom, is $400/bill a lot or reasonable? I do have one chicken coop and one animal shed.