Toyota has partnered with NEDO (New Energy and Industrial Technology Development Organisation) and electronics experts, Sharp, to further its development of on-car solar technology. It has created a test bed, based on a PHEV Prius, to ascertain the viability of solar charging as an additional energy source in terms of both cost and performance. To this end, the three-piece partnership is testing cells that are far more efficient than most.

The cells, which adorn the Prius in a somewhat less refined way than on the recently revealed Lightyear One, are Sharp 'triple junction' units. These have been knocking about since 2013 and, in testing, have been able to deliver efficiency of over 44 per cent and were primarily designed for use on satellites. In this application they are said to be operating at closer to 34 per cent.

Power derived from the solar cells, which are located on the bonnet, roof and boot of the Prius, maxes out at around 860 watts in ideal conditions. This equates to an additional 27 miles of charge through static charging (when the car is parked) and, interestingly, can extend the Toyota's range in electric-only mode by approximately 35 miles. This is some way off of the Lightyear's claimed charging performance, but then again it's doubtful that whatever Toyota might finally release for sale will cost £150 grand...

At present, Toyota offers a cost-option of solar charging to its PHEV Prius but it is a very modest system capable of just 180 watts (at 22 per cent efficiency) and an additional four miles of range over the course of a sunny day. While driving in electric-only mode, it merely supplies power to the auxiliary battery.