According to industry standards, power surges inside a building can reach up to 6,000 Volts, and 3,000 amperes, and deliver up to 90 joules of energy.  90 Joules is not a lot of energy.  To put that in perspective, it would raise the temperature of a bottle of water about one degree F.  But since the surge energy is delivered in less than 100 microseconds, the amount of power exceeds 18,000,000 watts of power!