The answer is simple: only a little. The exact power consumption when Gravaa actively inflates your tires depends on many factors, as the Technology page explains. On average, the power consumption is 4 Watts (per wheel) when inflating and 0 Watts when the system is no longer inflating (deflation requires no power, of course). The power Gravaa does draw (when active) is more than compensated by the advantages you will achieve by riding with adaptable tire pressure; with less friction/rolling resistance or improved traction, you stand to beat your friends or competitors.