Amp-hour (Ah) Capacity
The unit for the amount of charge a battery can deliver at a given discharge rate; 100 Ah means a store that can sustain 5 A for roughly 20 hours. The value depends on the discharge rate and in RV batteries it is usually given with a 20-hour discharge (C20) reference.
Amp-hour is current multiplied by time. However, in lead-acid chemistry the total charge obtained decreases at fast discharge: the same battery that delivers 5 A for 20 hours lasts noticeably shorter than expected at 50 A. That is why it matters which discharge rate the catalogue value belongs to.
To make an energy calculation the Ah value has to be multiplied by the voltage: 12 V × 100 Ah ≈ 1.2 kWh. Only in this way can systems at different voltages be compared.
In RV planning the method is simple: you multiply the current of each load by its running time and add up the daily Ah consumption. LED lighting typically draws a few hundred mA and the water pump a few amperes while running. A levelling system with 12 V DC jacks such as the KTS200 draws current only during the cycle; its share of the daily total is small, but because its instantaneous current is high it is assessed separately in terms of cable cross-section and battery internal resistance.
The context in which this term is used: How to choose levelling jack capacity