Amp hours are what the batteries are specified in, right down to cells that are 1.5V, 2V, 3.9V etc.. Yes, once they're in system you want to know kWh capacity of the system as a whole, but it makes sense that people think of what's written on the batteries first.
caymanjim knows his units, but the general public is so ignorant that it's common to hear people confusing a 1200-amp-hour battery with a 1200-(cold-cranking-)amp battery. even people who built a multi-voltage electrical system for their rv. the struggle is real
