When a lower cost solar power supply is needed, a Reduced Energy at Night (REN) type supply may be the answer. If you have a structure with little interference, such as a well casing with a good cement job or a coated pipeline, and the structure maintains polarization and can be polarized during the daytime, a REN type power supply will do the job. Only a fraction of the current required to initially polarize a structure is needed to maintain polarization once the structure is polarized. 
   The Reduced Energy at Night (REN) power supply is designed to provide 100% of the daytime current rating during daytime solar energy periods and a minimum of 1/2 the daytime current rating of the power supply at night. This reduces the size and quantity of components required resulting in lower power supply costs. REN type regulators provide the customer with the ability to adjust the output voltage  electronically from zero to the rated output of the power supply. The unit automatically drops to 50% of the daytime output current during periods of darkness. 
   REN type units are shipped with all required components for easy installation in the field.