Off grid power isn稚 truly free, LOL
No, it is not free, and a lot of times it ends up being its own lifestyle....a person's hobby onto itself. Which that is fine of course.
When you factor in heating a home though, and power generation combined; it really closes the gap on buying on grid power and domestic heat.
In this case, I am using what I got for major parts to make the genset, but if I was to buy the gensets instead, I think a better approach would be to buy smaller units, and then synchronize the two together when they were needed. The cost of syncing equipment is not that expensive, and would allow one engine to run when a smaller amount of power is needed, or when heat is needed. I say the latter because it would only take one engine, at half the size, for all my heating needs. I would just need a secondary genset to fire up for the bigger electrical loads.
It has been years since I worked for the railroad and synced in AC gensets, but that was using analog controls, so I imagine today, with digital technology, it is probably a lot easier, and probably could be automated. Maybe set the second genset to lag, then have it fire up at 75% load on the first? Maybe run use one as primary, and one as back-up so that every 30,000 hours you replace just one. Or maybe alternate the units so that you get close to 60,000 hours out of them before both have to be replaced? (I do not know...same, but different I guess).
When I did the math on one bigger engine, with combined heat and power, using plug and play gensets and fuel consumption, it worked so that I was within $1200 of buying propane and buying on-grid power 24/7-150 days. Since then, propane has gone up, and grid power just went up 2% on a PUC approved KWH hike, so it is even more favorable then when I first ran the numbers. I think with a two genset setup, a person could get bought power and heat closer to self-produced power and heat...150 days (the heating season here).