On the surface, it makes little sense to put a big battery bank next to a commercial solar array. As it is, solar power is still more expensive than the grid in many places, so adding pricey batteries would just push the cost of energy up more. But what if you could finance the energy storage equipment, much the way solar panels are financed, and the batteries provided a revenue stream? In an off-grid-solar scenario, old-school lead-acid batteries are just there to provide power at night and on cloudy days. But modern grid-scale battery systems are only put in place to save money or provide services to the grid.