Basically, any bike can be converted to electric. Whether or not it makes sense to do so depends on the end goal. If you have a very specific bicycle you love and want to convert, it might make sense. If you're looking just to save money and time, probably not.
A conversion can sometimes take nearly as much money as buying a readymade electric bicycle. If you love tinkering and building however, sometimes the money doesn't matter as much!
We do stock some kits and parts for converting your existing bike. In order to determine if it will fit, we would need the following information:
For a hub motor:
Rear Dropout width in mm
Size of your existing rear wheel (diameter and width)
Type and number of speeds on rear wheel (cassette or freewheel, 7 speed, 8 speed, etc)
Bottom bracket width (for mid-drive motor)