A 110-volt block heater typically uses between 400 watts and 1500 watts of power. Most block heaters that are larger than 1800 watts require 220-volt wiring.
The average cost to operate a 110 volt device overnight for ten hours when needed is $90 per year as of 2014, assuming an electrical rate of $0.11143/kWh. Wisconsin Public Service recommends installing a timer that starts the heater approximately two hours before the driver intends to start the vehicle, which reduces the cost by $70 or more annually at this rate, depending on the size of the heater.
Block heaters make vehicles easier to start when temperatures are cold outside. They connect to a power outlet through a cord fed through the grille of the vehicle. Warming the vehicle before starting keeps motor oil flowing more freely. The pre-warmed engine aids in fuel vaporization, to create less pollution than a vehicle using gasoline or other fuel to warm the engine.
The typical block heater inserts into a freeze plug hole that the manufacturer bores into the engine block. When in operation, it heats the metal of the engine, motor oil and coolant. In colder climates, vehicles often have factory-installed heater blocks. Aftermarket models are available for installation by a qualified mechanic or the owner.