DIY PV System to Save Money AND for SHTF

[Paul]

Like the plan but 600 watts as an absolute max won't go far.
Plugging into the shed could be an issue.
Depending on the cable run, quality, rating, you could have greater line losses than you think.
I always down rate current capability by 1/3 when running though (can I say dubious) wiring.

Earthing could also be an issue.
If your shed wiring is correct and up to code it'll be fed through an RCD.
That RCD will be referenced to the house earthing and in urban locations that's usually PME earthing.
I've had issues with external generator earthing fighting PME and lets face it, solar is just another form of generator.
You trundling round panels on long wires won't help either.
Copper losses are something to take into consideration.

Also, inverters are pretty good at dealing with the occasional surge but hate too much rapid inductive switching i.e. motors and their start up chokes even simple ones like central heating pumps.
PV systems use the mains to buffer this electrical noise, but as a stand alone system it's going to be hammered.
It's because of this I don't directly drive my mains preferring to use the PV inverter to run a separate 500 watt UPS.

Have you thought of providing a totally separate LV system?
Solar is not bad at keeping batteries topped up even in winter (with a much greater markdown in performance in reality to the book figures).
We've got a simple 12 VDC loop in our house powering PIR triggered LED light sources.
Walk anywhere in the dark round the house and it triggers a 6 X LED light.
Total load with everything on? 228mA.
(Took SWMBO and I running frantically round the hovel to keep everything on to test this)
Average, 60mA. That's cock all load.

Two great advantages doing this.
It leaves the UPS to run the essentials i.e. boiler and horrible inductive water pump, leaving emergency capacity for the VERY important camping kettle (120 watts)

I work slightly differently though to conventional PV systems though and during a power out, CH and other essentials are all swopped over to a separate circuit.
Bit of a bind but safer all round.