2L of water has a mass of 2 kg
15 degrees ac to oiling will make a deltaT of 85 degrees
cp for water is 4186 J/kgC
So Q = 2*4186*85 = 712 kJ = 676 BTU
of course this is over 6 minutes, so the power evolved by the RMH would be these numbers divided by 360 seconds. So approximately 2 kW of power.
These numbers are rough ballpark kind of numbers. Your water probably isn't pure water, so the density, specific heat, and boiling points will all be a little different. But still, your stove is putting out a fair bit of energy!
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