The number of PV installations on buildings connected to the electricity grid has grown in recent years. Government subsidy programs (particularly in Germany and Japan) and green pricing policies of utilities or electricity service providers have stimulated demand. Demand is also driven by the desire of individuals or companies to obtain their electricity from a clean, non-polluting, renewable source. These consumers are usually willing to pay only a small premium for renewable energy. Increasingly, the incentive is an attractive financial return on the investment through the sale of solar electricity at premium feed-in tariff rates.
In solar systems connected to the electricity grid, the PV system supplies electricity to the building, and any daytime excess may be exported to the grid. Batteries are not required because the grid supplies any extra demand. However, to be independent of the grid supply, battery storage is needed to provide power at night.
Holiday or vacation homes without access to the electricity grid can use solar systems more cost-effectively than if the grid was extended to reach the location. Remote homes in sunny locations can obtain reliable electricity to meet basic needs with a simple system comprising of a PV panel, a rechargeable battery to store the energy captured during daylight hours, a regulator (or charge controller), and the necessary wiring and switches. Such systems are often called solar home systems (SHS).