“ A 3kg cat has a heat output of 14.8 watts, or 129.65 kilowatt-hours...”
Playing fast and loose here. That’s 129.65 kilowatt hours per year. 14.8 watts is 0.0148 kilowatts of course. Kilowatt hours are a measure of total energy output over a given time not instantaneous output.
Also that's kWh summed up over the year. Cats have constant output, but for house heating you'd want to concentrate it to just ~3-4 months. So we're closer to 50-60 cats at that point.
You would be surprised how often this error is made. Even in quality newspapers journalists tend to use kWh as a unit of power instead of energy. That probably happens because of the 'hour' part in kWh.
People have no problem understanding that km is distance, and km/h is speed.
With energy and power the units read less intuitively: energy is J (Joule) and power is really just J/s (Joules per second), but we call that W (Watt) and for purposes of energy consumption the unit is kWh, which is really just a fancy compact way of saying 3.6 MJ (Megajoules).
So we have journalists writing about new dams that produce x TWh and cats that produce 129.65 kWh. (Per what? Day? Month? Year? Lifespan of the dam?)
Playing fast and loose here. That’s 129.65 kilowatt hours per year. 14.8 watts is 0.0148 kilowatts of course. Kilowatt hours are a measure of total energy output over a given time not instantaneous output.