Smart metering is an essential element of the future smart grid development. However, frequent data collected by home smart meters reveal a wealth of information about residential appliance usage. This gives rise to the smart metering privacy problem. Smart metering data privacy can be protected by using a battery to mask energy usage profiles. However, such a system privately modifies usage consumption patterns and it may induce a cost depending on battery performance and dynamic utility pricing. The aim of this paper is to show a) how information theoretic anonymity metrics can be used to measure the privacy protection offered by a water-filling power transformation algorithm, b) how a good level of protection and a low maintenance cost can be obtained with reasonably sized batteries, and c) what is the impact on the utility and price. Our initial cost analysis results suggest that it is possible to communicate granular smart metering information, protect the consumers' privacy at a low cost, and promote load balancing in the smart grid. That renders our privacy protection system affordable.