I know that it's 450 kilovolts because the breakdown voltage of atmosphere at sea level is ~30 KV per cm of distance.

Even if you say that his capacitance is lower because he has two jars in series, because they are identical the capacitance is half, they are still 100 watt sparks in that case, which would work out to 50 watts per second generated on average, with one hand, relaxed, with very little resistance.

I know that it's 450 kilovolts because the breakdown voltage of atmosphere at sea level is ~30 KV per cm of distance