MM since the power drop is a factor of current and the resistance, the higher the voltage, the lower the current, the less power lost, thus the 400,000V supergrid to move power any distance, 132,000V , 33,000V then local down to 11,000V. percentage losses are in the region of small numbers 3% maybe, transforrmers are 98%efficient most losses are at mains voltages, maybe up to 5%