There is a standard for smart meters called DLMS [1]. It's the most used protocol for smart meters for a while now. The protocol supports two way authentication and uses AES-GCM.
Providing a secure medium for meter communication is in the interest of both the user and the power companies: Users are protected from malicious commands to the meter (using the breaker to disconnect your power, changing the used tariff, ...) and power suppliers prevent fraud.