The ADF model 2100 pressure washer offers a little less water (3.5 GPM) and more pressure (2100 PSI) which makes this brother to the Model 2000 desirable when the water system is marginal or you want to save water, but you need the pressure for those hard to clean applications. The model 2100 can be powered by either an electric or gas engine. It requires a 220 or 440 volt electrical connection, and the water can be heated by oil, gas, or electricity.