A startup hopes to crack Germany’s residential energy storage market with a flow battery, despite problems for the technology elsewhere.

VoltStorage, of Olching, Bavaria, is commercializing Europe’s first redox flow battery for home use in a move that echoes Redflow’s brief excursion into the residential market in Australia.

The VoltStorage Series 100 battery, with 3.6 kilowatts and 6.8 kilowatt-hours of capacity, was being offered at a preorder price of €5,999 (about USD $7,060). It is not clear if this price includes installation costs and sales tax.

For comparison, the 4.6-kilowatt, 13.5-kilowatt-hour lithium-ion Tesla Powerwall sells for €7,350 ($8,650) in Germany, including supporting hardware and 19 percent sales tax, with installation costing up to a further €3,300 ($3,890).

Assuming the VoltStorage price excludes installation but includes sales tax, buying the flow battery will cost more than a third more per installed kilowatt-hour of capacity than the Powerwall.