Voltage: 220 – 240 V, 50 Hz (same as the rest of continental Europe)
Socket type: Europlug /Schuko with two round pins.
Adaptors are needed for appliances made for countries outside the EU.
Some hotels might offer an adaptor but it is best to carry your own.
Adaptors are hard to find in Bulgaria outside big cities.
Big electronic stores like Technopolis and Technomarket and the bigger gas stations usually sell them for approximately 10 lv (5 euro).