I've been commuting by bicycle for around 9 to 12 miles each way (depending on my route), over a change in grade of around 200 feet, for the last several weeks, on a hybrid bicycle. I've found that the weekends are an invaluable couple of days for my knees to recover each week, since I don't currently have a vehicle available to me.
I'm strongly considering either adding an after-market electric bicycle kit to my existing bicycle (a 2001 Giant Cypress), or buying a new bike made specifically for commuting. Having read as many descriptions as I can on electric-bicycle.com, though, I'm entirely confused as to what would be best for me.
My steepest incline on my commute (and on my preferred long-distance routes) doesn't exceed around 5 or 6 degrees, and I'd love the opportunity to be able to ride metric and imperial century routes again-- because of bursitis in both knees, I can no longer do this under my own power if there are uphills in the route. I miss being able to enjoy those nice long rides, though.
I am NOT looking for a moped. I want to pedal across the flats, coast the downhills, and enjoy an electronic assist on the uphills (but without turning it over entirely to the motor-- I still want -some- exercise out of this!).
In general, when my knees could handle more, on a crushed gravel trail in Pennsylvania, I handled an average of 13.5mph. Lately, I'm only averaging 8.5mph. This is adequate for my current commute, given the slopes in between home and office, but I'm interested in doing better.
Basically, I want to switch to an electric bicycle, if for no other reason than to improve my uphill efficiency. I'm not into racing, I don't normally ride in groups, and I don't care what my maximum downhill speed is. I just want to be able to ride uphill without killing my knees!
So... given that, what electric bike (under $US 1500) would you recommend?