And be off-grid? Or just be energy-cost neutral? If you want the latter any number of folks can get 'zero cost' panels put on their roof by agreeing to buy their power from the panel installer instead of PG&E.
Off-grid is harder since there is a ton of maintenance that goes on with battery systems. That said, for a single family detached home, we're getting close to the point where there would be enough volume in the foundation / floor for charge storage in "super" caps. When we were installing the 5.2kV system on our house we looked at Maxell supercaps and it would have added another $122,000 to the install but you could have nominally fit them under the house (about 1800 sq ft of crawlspace). The reason I think such things would be better off being built into the foundation is that you really really don't want a rat to urinate on your system and cause a (brief) short. A lot of energy that can come out way to fast to be safe.
Off-grid is harder since there is a ton of maintenance that goes on with battery systems. That said, for a single family detached home, we're getting close to the point where there would be enough volume in the foundation / floor for charge storage in "super" caps. When we were installing the 5.2kV system on our house we looked at Maxell supercaps and it would have added another $122,000 to the install but you could have nominally fit them under the house (about 1800 sq ft of crawlspace). The reason I think such things would be better off being built into the foundation is that you really really don't want a rat to urinate on your system and cause a (brief) short. A lot of energy that can come out way to fast to be safe.