The effect of environmental conditions on photovoltaic modules is presented in this work. The average terminals voltages of three solar panels of 6, 12 and 33volts mounted on a gabbled rooftop of about 15meters high were examined for different priods.The result from the experiment reveals that the 6, 12 and 33volts panels by 7.30am generate their respective rated voltages. Further examination shows that between 12.00noon and 1.00pm local time, the panels output were maximally 9, 20.2 and 38volts respectively. Beyond 6.30pm the voltage readings from the panels decreases virtually to zero. Plots of the average voltage generated for different periods revealed time and cloud dependence. The voltages generated also depend on its angle of inclination with respect to the sun and location of the site. The result from the experimental data depict that photovoltaic power generated is sustainable and can satisfactorily power both domestic and industrial loads for capacity building.