The Powys-based company - owned by Hugh Spowers - will begin trialling their new cars during 2018 and currently have 750 people signed-up for the pilot scheme, the Wired reported.
Spowers said: "We should have the first car running in January and we should have the 20 built and in operation by June."
During the trial the cars will be tested on a broad range of users and this includes members of the public, private sector companies.
Originally, Riversimple were supposed to test 20 cars in the UK but missed its self-imposed target.
Spowers said: "It is a low car and it is a very low seat. We want to see how older people will react to it.
"As soon as we've got these cars built, our design programme forks.
"The production version by-and-large will look the same. The surfaces will be changing slightly, we're going to be doing more aerodynamic work."
Riversimple has set itself the target of bringing its vehicles to market towards the end of 2020.
The car is powered by a hydrogen fuel cell - which combines gas with water to create electricity - and can have a range of up to 300 miles.