Despite being British, the British Virgin Islands use imperial measures: Miles, feet, and pounds are the common parlance. Speed limits are posted in miles, gas is sold by the gallon, and groceries are weighed in pounds and ounces. The same is true for the U.S. Virgin Islands.
Electricity is 110 volts, 60 cycles, the same as in the United States. No transformers or plug adapters are required. Both the U.S. and British Virgin Islands experience occasional power outages, but many hotels and guesthouses have backup generators so you may not notice.
The Virgin Islands  are on Atlantic standard time, one hour earlier than eastern standard time and four hours later than Greenwich mean time. There is no daylight saving time.