A surface mount energy storage device in the form of a supercapacitor (1) includes a generally rectangular folded prismatic housing (2) and two energy storage elements (not shown) that are sealingly contained within the housing (2) and which are connected in series. A mount, in the form of an integrally formed tinned metal frame (3), extends about and captively retains housing (2) in the folded configuration shown. Two terminals, in the form of elongate contacts (4, 5) extend from the energy storage elements and terminate outside housing (2) for allowing external electrical connection to the elements.