High capacitance electrical capacitors
These are supercapacitors you are talking about. A lithium ion battery of the same energy capacity will both cost and weigh 10% as much or less. Capacitors are therefore only considered where power density is of concern (how fast you need the energy to be available, such as in high intensity camera flash units or electric detonators for explosives for example), in which case chemical batteries can't compare. 

For home use, slow, steady and sustained is key, so electrochemical storage is here to stay for many years. Not to mention $$$.