While the effects of street-canyon configuration on temperature, wind speed and direction, and air quality have received much attention, its impact on solar energy potential has not been much studied. This paper focuses on two aspects of the street-canyon configuration in the city of Geneva in Switzerland: (i) Quantifying its canyon geometric characteristics, including the widths, orientations, and aspect ratios of 1600 street canyons. (ii) Comparing the geometric characteristics with solar irradiation (kWhm-2) of street surface. The results show, first, that the solar irradiation is greatest for the months May to August and that street canyons orientated roughly WNW-ESE, that is, streets facing SSW. Second, street canyons with low aspect ratios (<1.0) and oriented WNW-ESE receive the greatest solar irradiation. In particular, when the aspect ratio reaches 0.5 in May and August, and 1.0 in June and July, the monthly solar irradiation falls below 70 kWhm-2. Third, street canyons of great widths (> 10-30 m) and oriented WNW-ESE receive the greatest solar irradiation. More specifically, the solar irradiation falls below 70 kWhm-2 in June and July for streets narrower than 10-15 m, and below the same value in May and August for streets narrower than 20-30 m.