The cost of electricity to power a Z series forklift is typically between 12 to 15 percent of the cost of how much it costs to power an internal combustion (IC) forklift. A standard IC forklift can only operate up to eight hours a day before needing be to refueled. That means you constantly need to purchase fuel to keep up with the demands of your workplace. Also, most IC forklifts are made without a built-in gas gauge, making it harder to monitor tank levels for refueling.