Powervault uses either Lead Acid or Lithium-ion Phosphate battery technology to store energy in your home. The Lead Acid Powervault has a lower upfront cost but doesn't last as long as the Lithium-ion Phosphate Powervault. The Lead Acid Powervault's batteries have a lifetime of 5 – 7 years. The Lithium-ion Phosphate Powervault's cells have a lifetime of 11 – 13 years. It is possible to buy a Lead Acid Powervault now and, in 5 – 7 years when the batteries reach the end of their useful life, then upgrade to Lithium-ion Phosphate cells.