These are the simplest of solar-electric systems, with the fewest components. Because they don’t have batteries and are not hooked up to the utility, they only power the loads when the sun is shining. This means that they are only appropriate for a few select applications, notably water pumping and ventilation—when the sun shines, the fan or pump runs. At night these systems do not provide energy. These systems require a match between the PV modules and the load, and may also have electronics between the array and load to facilitate start-up and maximize energy production.