This is a unique product designed, developed and manufactured by Sunair Power for inline power measurement from Solar. The SPM1500is a DC Wattmeter and Totalizer in one. The LCD screen switches between live readings of Voltage, Current, Power and various parameters on one screen and then switches to a second screen to display totalized readings. This is very useful in determining the state of your power supply system and will allow you to maximize the power harvested by Solar PV or Wind.