Optimising the voltage will not cause lights to dim; lighting levels will be maintained within their original design specification. Remember that the powerPerfector is bringing the voltage from an 'over-voltage' (240V) to the correct, design optimum voltage (220V), so as a result the lighting output will be at the designed level, and the efficiency and longevity of the lighting system will be maximised. We have never had a report of a discernible drop in lumen output following a powerPerfector installation.