from this thread
As I have posted before, it isn't a watts to Ah ratio that matters.
Having said something before doesn’t make it any more true.
It is the ability to produce more than you need in the worse conditions that you will be in.
New folks don’t know how to calculate that or they wouldn’t ask similar questions in thread after thread.
The 1:1 - 3:1 ratios are intended to get them into the ballpark. It works.
So again it is the ratio of watts to your needs in the worse conditions.
The house bank is sized to the camper’s needs. Therefore these two statements are functionally equivalent for our purposes:
“it is the ratio of watts to your needs in the
“it is the ratio of watts to the bank capacity in the worst conditions”
Need 100 watts in ideal conditions could mean 300 in bad.
It is shocking how well this lines up with the 1:1 - 3:1 rule of thumb. I hope everyone is starting to see why. It is the same idea expressed two different ways. Saying “1:1 in good conditions and up to 3:1 in bad conditions” is simpler to understand and remember.
And that’s how rules of thumb are supposed to work.