Nissan has entered a new market already served by Tesla Motors’ Powerwall energy storage units.

The partnership between U.K.-based arm of the Japanese automaker and Enel SpA, Italy’s largest utility, will let Nissan EV owners sell excess energy back to the grid. That excess energy from the electric vehicles will be stored in energy storage units separate from the vehicles.

Presently, the deal would apply to Nissan Leafs and e-NV200 electric vans which can sell excess energy from their lithium-ion batteries during periods of peak demand to the utility. These electric vehicles serve Nissan and Enel as mobile power sources competing with offerings from battery storage products such as Tesla’s Powerwall battery.

“We believe electric vehicles can become a mobile power unit,” said Paul Wilcox, Nissan’s chairman for Europe. “Customers can save money on their energy bills.”

Nissan and Enel will be doing a trial run by identifying 100 Nissan electric vehicle drivers willing to try out Enel’s “vehicle-to-grid” software. That software allows electricity to be traded through National Grid Plc, a British utility company. If the trial program is a success, it will be rolled out on a commercial basis, said Ernesto Ciorra, head of innovation and sustainability for Enel.

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The energy storage unit, which has been named “xStorage,” unit will be available in October and was developed by Nissan and Cleveland-based Eaton Corp. The system will be priced starting at 4,000 euros ($4,556) and will be available across Europe.

The xStorage units will be more costly than Tesla’s offering. Tesla’s 7 kWh Powerwall is $3,000, and the 10 kWh unit sells for $3,500. Initial Powerwall shipments went out to the U.S. and Australian markets.

Nissan is hoping selling excess energy will make its electric vehicles more attractive to U.K. consumers. Incentives for purchasing EVs in England ended earlier this year.

Consumers in the U.K. had been able to access an EV rebate program. Previously set to run out last fall, U.K. government officials expanded the rebates to spur more sales of EVs before the incentive program ended in February 2016.