Unlike most Android OEMs, Apple does not include battery capacities in its spec lists for iPhones. However, it may be a particularly pressing issue this year, as the new 12 series has gone 5G, something that may eat screen-on time. A Dutch carrier has listed actual milliamp-hour figures for all 4 variants, and they make for worrying reading.
Apple never releases the actual capacities of its flagship iPhone mobile devices on its own site, preferring to make claims for their longevity instead. However, a Dutch carrier claims to have found out more concrete specs for every variant of the new 12 series. According to it, none of them exceeds its predecessor in this respect.