  We propose an online pricing mechanism for electric vehicle (EV) charging. A
charging station decides prices for each arriving EV depending on the energy
and the time within which the EV will be served (i.e. deadline). The user
selects either one of the contracts by paying the prescribed price or rejects
all depending on their surpluses. The charging station can serve users using
renewable energy and conventional energy. Users may select longer deadlines as
they may have to pay less because of the less amount of conventional energy,
however, they have to wait a longer period. We consider a {\em myopic} charging
station and show that there exists a pricing mechanism which jointly maximizes
the social welfare and the profit of the charging station when the charging
station knows the utilities of the users. However, when the charging station
does not know the utilities of the users, the social welfare pricing strategy
may not maximize the expected profit of the charging station and even the
profit may be $0$. We propose a fixed profit pricing strategy which provides a
guaranteed fixed profit to the charging station and can maximize the profit in
practice. We empirically show that our proposed mechanism reduces the
peak-demand and utilizes the limited charging spots in a charging station
efficiently.
