Flash's 500-watt motor has been specifically tuned to perform well on hills. That said, we can't guarantee specific performance data for hills, since that depends on a variety of factors, including hill grade, rider weight, road/weather conditions, tire pressure, etc.
However, to give you an idea of uphill performance, our test riders regularly climb an 8% grade using throttle only (no pedaling), at speeds of 10 mph. They also have an easy time climbing a 12% hill using full pedal assist.