I had 2, 500 watt, front wheel, Golden Motors, EBike kits.
I put them on Wal-Mart mountain bikes in 2007 and 08.
I used a 25AH, 36 volt, lifepo4 battery for mine, since I had bad knees, and 20 AH for the DW. We both weigh over 200 lbs.
We used them, as our transportation, for 5 years, while cruising the east coast. We also had a, 2 child carrier , for grocery shopping.
The front wheel added some weight to the bike, but being a direct drive, hub mounted, brushless motor, it added no resistance.
I believe our longest, battery killing, trip was 16 miles, at the full speed of about 15 mph. We recharged at a friends dock, and returned to ours.
During one of our Eria Canal rides, we traveled over 30 miles, during an all day ride, before recharge. Of course, we did save power, by pedaling, while using the electric to assist, and the canal trail is flat.
Due to salt water exposure, we retired the bikes and stored the wheel kits, last year. We have been settling down in the Keys, for the winters and keep a car with us.
If you are in good shape, I would recommend the 250 watt, rear wheel kit and 15 AH battery, from Golden Motors.