The electricity standard is 110 volt AC, the same as in the US and Canada. Three prong outlets are not readily available, so an adaptor is a good idea. Electrical stores in Cancun have them in stock. The larger hotels have converters for most 220-volt devices. Mexico does not use a ground wire in its electrical wiring, so power surges are a common problem. If you plan to use a laptop computer, you should invest in a surge protector sold in Mexican electronic stores.