The electricity in Prague is 220v. The sockets take the two pin plug with round pins so keep this in mind and bring an adaptor. If you forget your adaptor then you can get one in a hardwear store (železářství) or Tesco. The Tesco on Národní Třída has it´s electrical department on the top floor and is almost certain to stock adaptors for adapting three pin to two pin plugs. Americans and Canadians will need a transformer to change the voltage.