Simply put, a Volt is a unit to measure electrical current. 

Volt is the measure of potential difference which causes a current to flow through, having some resistance in the medium. Or in more technical terms, it is the SI unit of electromotive force. It is the difference of potential that would drive one ampere of current against one ohm resistance.

Volts are the amount of voltage, electrical current, required to run a solar hot water pump.
Water pumps that run on PV can handle the voltage fluctuation that solar panels produce. Nonetheless, pumps are primarily designed to run on their stated voltage. For example, 12V DC water pumps should run on a 12V PV panel. 24V DC water pumps on a 24V PV panel.
Constantly running a water pump on higher voltage will increase the speed on the pump. Doing that will greatly reduce their life expectancy. Running the pump on a lower voltage will in turn slow the speed of the pump. In contrast to the first example, this does not reduce the pump’s life expectancy.
If you have any questions or doubts, feel free to contact us. We’d be happy to answer any query!