The Polar Night Energy team acknowledges this but argues that a sand battery is a far more cost-effective solution. The team has calculated that their battery is eight to 10 times cheaper than a lithium battery which stores the same amount of energy. To generate 8 MWh of energy using the Kankaanpää sand battery costs about $200,000 (£174,000), says Eronen. A lithium-ion battery storing 8 MWh of energy would cost at least $1,600,000 (£1,391,000), he says.