Hi BFL13,
If the solar is to be autonomous and not rely on (gasp) a generator, then it behooves the designer to have the possibility to equalize. If you accept (Mexico Wanderer does) that 5 amps per 100 amp-hours of storage is the bare minimum to allow that to happen, then a well designed system, where no other charging source is to be used should meet that 5 amp window. This translates to about 60 watts per 100 amp-hours.
A small battery bank may show a greater depth of discharge--so more solar is needed per 100 amp-hours. For a larger bank of say 500 amp-hours the three hundred watts of solar may be enough to return all the energy used.
If an inverter is used then the amount of energy used may skyrocket. I can and do run my air conditioner from the battery bank. That draws about 140 amps. To replace that energy use with solar may be too much of a challenge, even if I go to MPPT and very high output panels.
