The Switch’s battery seems to be better than many expected it to be. According to Ars Technica’s preview, the console’s charge went from 100% to 98% after spending eight hours in sleep mode. This is indeed a good sign to those concerned about the battery life on the console, but rechargeable batteries are notorious for wearing down over time though, so take with a grain of salt.
Battery life so far conforms to Nintendo’s stated specs—I can get about three hours of portable Zelda play on a full battery charge, depending on the screen brightness. The included AC adapter seems to fill about 1 percent of the battery per minute (give or take) when the system is in sleep mode (that mode is very power conscious, incidentally—after eight hours in “sleep,” a fully charged battery had only drained to 98 percent).