Free Solar for worth getting for after the SHTF?

[Tarrel]

I've heard of people having difficulties selling their house with "free" solar panels installed. As an earlier poster said, it is the equivalent of having a sitting tenant, which means that a mortgage can be hard to come by.

If you're house is well insulated, it still makes sense to go for buying your own grid-connected system and gaining the income from the feed-in tarriffs. (These are roughly double for a house that meets EPC band C or above.)

I've looked into this a lot and, to be honest, the best solution if you want an off-grid, post-SHTF solution is to set up a separate system for off-grid, using 12V panels, a battery-bank and an inverter. For short-to-medium term power outages you can use extension leads from the inverter to your critical appliances (freezer, lighting, etc). In a total SHTF situation with permanent loss of grid power you can then re-wire your domestic circuits to run off the inverter.

Most grid-connected systems run at too high a voltage to be easily connected to 12V battery systems. If your panels run at, say, 72V you could set up 6 x 12V batteries in series to accept charge at 72V, but you'd then need an inverter to step up from 72V to 240V, and these are not easy to find compared to 12V or 24V ones.

So, in summary, probably better to see an off-grid solar back-up system and an on-grid money-saving system as two different things, although the idea of combining them does seem attractive.

---

Edit to add: As someone has mentioned, all grid-connected systems have an "Islanding" function that automatically shuts down the inverter in the event of grid failure. This is to prevent your power feeding into the grid and zapping the poor guy who's trying to fix the power outage. So, all the folks with grid-connected solar PV on their roofs will lose power in a power-cut, just like everyone else.