Most commercial controllers display the temperature of the hot water in the store and provide general status information about the system, including overall energy production.
Controllers provide an overrun time to extract some of the heat energy left in interconnecting pipes after the panels cool off.
They may also implement certain safety features such as cooling the store when it exceeds a preset temperature such as 65 °C, by sending excess heat back to the panels to be given off to the environment.
One claimed advantage of PV power is that it reduces the overall carbon emissions associated with operating the system since it avoids the need to supply this energy from fossil sources.
Neither of these options is really compatible with the simple direct-PV pump approach and so such systems are limited to using the less efficient flat panel collectors.
[citation needed] The benefits of a PV powered solar controller comes at a cost in reduced system performance in the range of 1-10%.
[1] This is due to heat losses at times when the panel may be hotter than the water store but there is insufficient sunlight to power the pump.