Ampere-hour (Ah)

An ampere-hour (Ah) is a unit of measurement for battery capacity, indicating how much electric charge a battery can store and deliver over time. One ampere-hour means a battery can supply one ampere of current for one hour.

In the solar industry, ampere-hours are commonly used to rate the capacity of deep-cycle batteries in off-grid and hybrid solar systems. For example, a 200 Ah battery at 12 volts stores 2,400 watt-hours (2.4 kWh) of energy. To determine the total energy capacity in kWh (which is more intuitive for homeowners), you multiply the Ah rating by the battery voltage and divide by 1,000. While residential lithium-ion batteries like the Tesla Powerwall are more commonly rated in kWh (13.5 kWh for the Powerwall), lead-acid and some off-grid batteries still use Ah ratings. Understanding ampere-hours helps homeowners compare battery options and calculate how much backup power they will have during an outage.