As of most recent estimates, the cost of a BESS by MW is between $200,000 and $420,000, varying by location, system size, and market conditions. This translates to around $150 - $420 per kWh, though in some markets, prices have dropped as low as $120 - $140 per kWh. Key. . If you want to know how many kilowatt-hours (kWh) of electricity the devices uses in an hour, or a day, or longer, just leave everything set up and read the display later. Monitors are especially useful for finding the amount of kWh used over any period of time for devices that don't run. . How much do a BESS cost per megawatt (MW), and more importantly, is this cost likely to decrease further? Are you an energy investor, utility planner, or just a fan of energy storage? You've landed on the right page. The cost per MW of a BESS is set by a number of factors, including battery. . The formula for calculating electricity cost is: To convert watts to kilowatts, divide by 1000: kW = Watts ÷ 1000 For a 2000W appliance running for 5 hours at $0. Enter the number of kWh used. .