Not sure if other energy suppliers are doing a similar deal, but E.On are giving away free energy monitors worth about ?45 to each customer. These wireless devices have an easy to fit clamp you place around the incoming cable to your home (read van), and they work out your current consumption and usage.
With the electric hookup we are not bothered about reducing cost, but they would be great for keeping an eye on loading, especially if you are on fussy sites on the continent.