North American appliances are compatible with Costa Rica's electrical system (110 volts) and outlets (parallel two-prong). Australian and European appliances require a two-prong adapter and a 220-volt to 110-volt transformer. Never use an outlet that specifically warns against using higher-voltage appliances without a transformer. Dual-voltage appliances (i.e., they operate equally well on 110 and 220 volts) such as most laptops, phone chargers, and hair dryers, need only a two-prong adapter, but you should bring a surge protector for your computer.
Walkabout Travel Gear. See "Solving the Riddle of Global Electricity" under "Shop Walkabout Travel Gear" for answers to power questions. 800/852–7085; www.walkabouttravelgear.com.