Solar power can be generated directly from photovoltaic (PV) cells that convert sunlight into electricity or indirectly from concentrated solar power (CSP) systems that use lenses or mirrors to focus sunlight. PV cells were initially used for small and off-grid applications but are now also being used in grid-connected situations as the cost of solar electricity falls. Solar power provides a renewable and relatively inexpensive source of energy where grid connections are unavailable or too expensive.