Volt Home Battery B10

Ten kilowatt-hours of lithium iron phosphate - the chemistry that gives up a little energy density in exchange for not being a fire risk in a garage - stacked to thirty if you need more. It charges from your own roof first and from the grid only when the tariff is low, and it holds the house up during a power cut, switching in fast enough that the computers stay on. Ten-year warranty, wall or floor mounted, and quiet.