The Video Doorbell is compatible with doorbell transformers that output 16-24 VAC (volts alternating current) with a maximum of 40VA (volt-amps). 16 VAC and 10VA is the smallest recommended transformer to power the Video Doorbell.
A doorbell chime operates on low voltage through your transformer. The transformer takes the standard electrical voltage, usually around 110-120 volts, and lowers it to approximately 10-24 volts.
Risk of electrical shock. Always use caution when handling electrical wiring.
Many builders install the doorbell transformer near the main electrical panel or inside the doorbell’s chime or bell housing for easy access. Voltage and Volt-Amps (VA) are listed on the transformer. This may appear as "max load" or "max power consumption rating."
Example of a US transformer
