Electricity in Portugal

Electrical Plug/Outlet and Voltage Information for Portugal shows useful photos of different kinds of wall sockets and which kinds of plugs work in Portugal. Hint: Not ones from the U.S.
It also says:
"But the shape of the socket is only half the story!
Electrical sockets (outlets) in Portugal (República Portuguesa) usually supply electricity at between 220 and 240 volts AC. If you're plugging in an appliance that was built for 220-240 volt electrical input, or an appliance that is compatible with multiple voltages, then an adapter is all you need.
But travel plug adapters do not change the voltage, so the electricity coming through the adapter will still be the same 220-240 volts the socket is supplying. North American sockets supply electricity at between 110 and 120 volts, far lower than in most of the rest of the world. Consequently, North American appliances are generally built for 110-120 volts.
But that doesn't mean that your specific appliance isn't already compatible with the higher voltage -- it may very well be."

According to this Adapter and Converter Finder:
"If you are bringing an American appliance or electronic device, you will need an Adapter Plug for almost every country in order to plug into their electrical outlets.
If that appliance or electronic device is not dual-voltage and you are visiting a country with 230 volt electricity, you will need either a Voltage Converter or a Transformer.
If you are planning to run your non dual-voltage appliance or electronic device continuously, you will need a Transformer."

Adapters are light and cheap but transformers are heavier and more expensive.

If you have questions, I'd recommend going to a travel store, such as Wide World Travel Store in Wallingford or Rick Steves' in Edmonds.