1, you can first reflect to the power supply department of your place, because the high voltage will burn the electric equipment, and may cause fire in serious cases; even if not burned, long time high voltage, but also use the power supply part of the electrical appliances to accelerate aging, affecting the life of the 250V, exceeding 220V by 14%, and according to the standard of single-phase power supply, it should be +7% and -10% of 220V. If the power supply department does not solve the problem, you can go to other relevant departments, such as the Consumer Council and other departments to complain and refuse to pay the electricity bill. High voltage is worse than low voltage!
2, the regulator has a regulator range of indicators, choose the one that can cover 240, 250V.
3, about the capacity, it is best to calculate the home often turn on at the same time the total power of the appliances, and then amplify the 1.2 times or so. Of course, you want to choose a larger capacity, it is not impossible, just pay attention to two points: a, the greater the capacity of the regulator, the greater the loss of itself, that is, the regulator itself to use electricity, even if it is not connected to any appliances, but also power consumption, the greater the capacity of its own more power consumption. b, in general, the greater the capacity, the higher the price.