  Incentive programs and ongoing reduction in costs are driving joint
installation of solar PV panels and storage systems in residential households.
There is a need for optimal investment decisions to reduce the electricity
consumption costs of the households further. In this paper, we first develop
analytical expression of storage investment decision and then of solar
investment decision for a household which is under net metering billing
mechanism with time of use pricing condition. Using real data of a residential
household in Austin, TX, USA, we study how the investment decisions would
provide benefit for a period of one year. Results show significant profit when
using storage devices and solar panels optimally for the system. It is
important to note that though our approach can help significantly to take
investment decisions, the solution will still be sub-optimal for somebody who
needs optimal investment jointly on both storage and solar systems.
