Electrolyzer produces more heat than description

aside from the heat created, its output gas temp is 70c

The output of the gases are fixed. And yes, it produces ~6W of Heat. For each  1000.0g/s of water. It heats the area and it sums up.

It produces: 6.25W oh heat as device itself(device heating and dissipate heat around itself) + 0.888kg of O2 at 70c + 0.112kg of H2 and 70c.

This all rough and my guesses but: heat capacity of O2 in game 1.005 J/g/Celsius or 1005 J/kg/Celsius so it releases 62470.8J of heat energy with oxygen, and heat capacity of H2 in game 2.4 J/g/Celsius or 2400 J/kg/Celsius ~18816J of heat energy with hydrogen. If it was real world i'd say that it release slightly more then 81.28kW of heat energy(because 1 J/s = 1 watt, and we have +81.28kJ each second so 81.28kW) but i'm not sure how many J/s in 1 ingame watt, probably 81.28kJ/s = 81.28W in game.

So in total, probably, electrolyzer would deliver 81.28W+6.25W of heat...  And it consume 120W of electric power, so it have ~32% efficiency(67% heat losses)? Most sure i'm wrong with my calculations, but yes it produce lot more heat then 6.25W

Also you should exclude heat that was carried with water on input. But in game it seems just destroy water no matter how much heat was there, and create gasses with static 70c temperature. So can make heat exchanger and heat cold water with hot gasses after electrolysis and destroy this heated water in electrolyzer resulting in 0 extra heat gain. Sounds wrong...