220 volts, standard European socket and plug
Electricity supply is 220 volts throughout Spain with 2 pin wall sockets.
Adapter needed for UK electrical plugs
If you want to use an electric equipment with a UK electrical plugs, you will need an electricity plug adapter that will convert the standard 3 pin socket into a 2 pin socket.
220 volts may ruin US electronic devices
Travelers from the US should obtain both an adapter and a transformer to operate American electronic devices.
Many American electronic equipments run on 110 volts. Connecting such device to a 220-volt electronic outlet may severly damage the appliance. To prevent that, apply a transformer to step down the voltage to 110 volts.
Many electronic devices run on both 110 and 220 volts. Make sure to check the voltage range your appliance is able to handle.