It's amazing how many Perpetual Motion scams seem to go with enthusiasm through the survivalist/prepper communities.
Be they Perpetual Motion, "Over-unity energy", "Stop bowing to the government/energy companies"... For a small price, you can buy the plans for a machine guaranteed(*) to produce more power than it uses.
(* Assuming you've built it correctly. We know it will work, therefore if it doesn't work for you, you haven't built it correctly, therefore you can't collect on the guarantee.)
Plus the many people who will sell you information on how to construct your own solar panels (as previously discussed).
One of my favourite authors in one of his books (fantasy, set in a world where magic exists but is unpredictable) says as part of the storyline how "dwarves had managed to make gold from lead - but what they hadn't heard is that they were doing it the hard way. The difference between the hard way and the easy one was that the hard way works." As the book progresses, you find that they had created a movable-type printing press (previously unknown).
So it is with anything - if anyone is selling you as easy something normally difficult, you can probably bet that it isn't going to work.
It's understandable - you look at situations, realise that you are vulnerable, or paying money that could be spent in other ways, and you'll want to cut expenses.
If people in such groups were of a more experimentalist bent, and more willing to go "See, it doesn't work" - and to listen to people who said such (without saying that said people are in league with commerce or government), then it might be something...
Likewise, you have plenty of communities being talked about - For Preppers, By Preppers - and if you don't subscribe to their beliefs, convenants, etc., you're not welcome. I've seen one or two planned that were based around the majority of people being involved in the community's single industry, typically fire-arms manufacture. With a noticeable lack of the normal amenities, gardens, farms, and... well, real self-sufficiency to which they claim to aspire.
I think, like perpetual motion scams, they might look good on paper, but probably aren't going to work as intended....