Wh to Ah converter

Amp-hours are what battery banks are sold in and watt-hours are what loads consume, so this conversion sits in the middle of every off-grid sizing calculation. Ah = Wh ÷ V, and the system voltage matters as much as the capacity: 1,200 Wh is 100 Ah at 12 V and 25 Ah at 48 V. That is the reason larger systems run at higher voltages — the same energy at four times the voltage draws a quarter of the current, which means thinner cable and far lower losses.

Depth of discharge is where the rating and the reality separate, and it is not a small correction. A lead-acid battery discharged below about 50% repeatedly has a drastically shortened life, so a 100 Ah lead-acid bank is a 50 Ah bank in practice. Lithium iron phosphate tolerates 80–90%, which is most of why it displaced lead-acid despite costing more per amp-hour — the usable capacity per pound is much closer than the headline figures suggest.

One caution about the C-rate: capacity is quoted at a specific discharge rate, usually C/20 for lead-acid. Draw the same battery at C/5 and you get noticeably less than the rated capacity, because of Peukert’s effect. Lithium is far less sensitive to this, which is another reason its real-world capacity holds up better.