High efficient central 24V and 12V power supply what shall supply all devices in a house of 7 flats

checked them but I do find only 24 V. In addition they state typical 90%efficiency which is not that accurate as I could choose between 92 %, 94%, … at other vendors.

Are there any proper power supply providing 24V AND 12 V as that would things make easier in regard of power supply sizing