However, service providers can add more photovoltaic systems at the current price. Because the total cost of the minimum required photovoltaic system becomes approximately half with $1.0/W solar modules, they can provide the same scale of energy supply to customers as the AP, which feeds 60 W constant energy to more 35.2% (= 60 x 24/4092) customers. It is interesting to consider the return on investment of additional photovoltaic systems, but that is outside the scope of this paper.