Prices for the bikes begin at 24 Euros per day, and are all set with "Lithium-ion batteries that support travel at up to 25 kilometers an hour (15.5 mph), with a range of 85 kilometers (52 miles)." The focus really is on getting tourists to see the Spanish countryside and seaside and away from the city centers, which would regularly either require a rental car that limits the scenery and route, or a regular bike which limits how far you can travel in just one day, not to mention relying on athletic skill to be pedaling for hours and hours.
The electric bikes open up new paths and new sights to tourists, plus more of them as you're moving faster. The Hertz electric bikes can be booked here. Warning: the site is all in Spanish, so have your Google Translate ready if you need it.