  A smart meter (SM) measures a consumer's electricity consumption and reports
it automatically to a utility provider (UP) in almost real time. Despite many
advantages of SMs, their use also leads to serious concerns about consumer
privacy. In this paper, SM privacy is studied by considering the presence of a
renewable energy source (RES) and a rechargeable battery (RB), which can be
used to partially hide the consumer's energy consumption behavior. Privacy is
measured by the information leakage rate, which denotes the average mutual
information between the user's real energy consumption and the energy requested
from the grid, which the SM reads and reports to the UP. The impact of the
knowledge of the amount of energy generated by the RES at the UP is also
considered. The minimum information leakage rate is characterized as a
computable information theoretic single-letter expression in the two extreme
cases, that is, when the battery capacity is infinite or zero. Numerical
results are presented for the finite battery capacity case to illustrate the
potential privacy gains from the existence of an RB. It is shown that, while
the information leakage rate decreases with increasing availability of an RES,
larger storage capacity is needed to fully exploit the available energy to
improve the privacy.
