Joe Seaton First add up the running watts on everything you want to power with the genset. Allow for surge current for things like well pumps and compressors used in freezers and refrigeraters. You should take a look at the next bigger size, it may not be that much more. I am using a Gen-Tran transfer switch also.
All sounds like you need to plan well . My boiler is turned off all year unless anyone wants a shower. If leccy goes we light a candle and I head out for the dark sky's with no lp . But for now I'm melting on the hearth rug wi a beer , and were sat in the dark , apart from her indoors watching tv