"KwH." You stinker.
Actually, how fast the total amount of energy is released could make it dangerous. If it's dissipated into a 100 Watt bulb, it would take 300,000 hours if I kept my decimals straight. If it's discharged into a copper bar, it could be explosive, like dropping a wrench across your car battery terminals.
Look at it this way. A spark from your hand to the wall electric plate after crossing the carpet may hit 20 or 30 thousand horsepower and yield a loud crack because the discharge occurs in microseconds.
But the total energy involved cannot possibly be more than the energy it took for you to shuffle across the carpet.
It's the time involved. You can't say 30,000 kWh is dangerous until you describe the timing involved.
Smaller quantities of energy are described in ergs or Joules, or electron Volts or foot-pounds and some other units. But a Joule is one Watt for one second, or one Watt-second. An electron Volt is 4.45049-23 Watt-hours. (0.000000000000000000000445049 Wh)
A foot-pound is 1.3558179483 Joules.
It depends on who's doing the describing as to what type of units are used.
For cartridges, it's foot pounds here in the US, overseas, it's Joules.
For cars, it's horsepower here and Watts over there.
Terry, 230RN