Ask This Old House plumbing and heating expert Richard Trethewey learns how to add storage to an existing photovoltaic array. SUBSCRIBE to This Old House: http://bit.ly/SubscribeThisOldHouse Time: 1 day Cost: Varies based on system size Skill Level: Professional Tools List: Drill/driver PVC pipe cutter Philips screwdriver Wire strippers Shopping List: AC Battery Electrical Conduit 12…