[Colorado Doug]

No doubt about it. IT IS VOLTS. I would guess less than 400 watts. Perhaps more than the reported 750,000 volts though. A friend and I built one in seventh grade. It kicked out about a million but at very low amps. Still, it would light up every light in the science lab. Mine was about the same size as this one.

They are pretty easy to make and pretty safe-at least on the secondary side. The input voltage is about 15,000 volts, 25 ma (an old neon light transformer) BUT! That goes through a capacitor made out of a 2'x2' x 1/4" glass plate with aluminum foil, glued on both sides. There is a spark gap of about 2" after the capacitor. That sucker has some JUICE at that point. That "low voltage" (15kv) gap sounds like a machine gun. It hurts bad if you get into the gap too! The gap at the capacitor will actually break the glass in time. The spark from the top of the secondary is high frequency and while much more voltage, it just bites a little.

The primary winding of my Tesla was about ten turns. The secondary is about a gazillion turns of 30 gauge magnetic wire. A small motor with contacts on a spinning dielectric disc just before the primary coil really ramps up the spark on a Tesla coil.

[Colorado Doug]

I take back the estimate of perhaps more than 750,000 volts for this one. I just saw the picture. This is a girly-man Tesla. A little sissy table top coil that I don't think could put out 500k. Mine was six feet tall.

[Colorado Doug]

a capacitor made out of a 2'x2' x 1/4" glass plate with aluminum foil, glued on both sides

Oh how I miss the smell of ozone. That sucker could have fixed the ozone hole in no time with the O3 that it cranked out. The glass glowed purple.