How much electricity does a battery recharge consume?

Just a little! For a 15kWh battery we will need 15kWh to fully recharge it. The cost depends on your electricity rate.
Supposing a cost of 25cent/kWh, we will spend 3,75€ for a full charge. Obviously, charging with a home photovoltaic system cuts the costs almost down to zero! Moreover, charging columns at shopping centres and in some public buildings are often completely free.