The company EGO developed a kit that you can retrofit to 70% of the bicycles. With 1,6hp of continuous power and 3,2hp in peak it allows to climb slopes up to 40 ° and reach speeds close to 70kph, the range is 40km.
The whole kit weighs 4,4kg (without the battery) the controller is placed in front of the bike (see picture below)
By the way where is the battery? It’s a LiFePO4 battery that you carry in a backpack, its weight is not communicated.
For the price, although it is not listed, an article (available on the site) of a German newspaper dated of September 2010 talks about 2222€… The same article quotes one of the creators who says that fitting the kit takes approximately 60 minutes to a good mechanic.