Don't know if it's a concern to you, but I recall that some companies could gather a hell of a lot more information than just your energy usage if they had access to your home supply.
IIRC It's to do with electrical signatures.
i.e. They can tell when you turn your TV on, the kettle on, or the gas boiler fires up (it's connected to the leccy supply) and so on.
Some devices can even leak more detailed information back due to the ring mains acting like receivers.
Van Eck phreaking is one method: https://en.wikipedia.org/wiki/Van_Eck_phreaking