Resistive heating is 100% efficient, they are saying 96% for microwave, meaning you will need 4% more power to achieve the same heating either in a tank or no tank.
Yes, I wasn’t suggesting that this solution was more efficient, but that solutions that are more efficient than what they replace are what we should be focusing on. It’s fine to say that resistive is 100% efficient, but my point was that a 10kW instant electric heater is not enough to meet the demands of many households (and falls well short of a gas boiler output) and you can’t just say install a 20kW electric heater because typically household supply is not built for that. And so if you heat a tank of water (a typical immersion heater is 3kW) then all of a sudden you have heat loss and you are nowhere near 100% efficient.
Again the discussion being resistive versus microwave, restive should be better even in an instant water heater, again microwave has no advantage that I see.
And when talking about efficiency you must specify context. In this case heating water via electricity, not losses of storing the heated water which is a separate issue based on tank vs instant regardless of heating method.
I am curious what form of energy you think the other 4% turns into?
Both systems are 100% efficient at turning electricity into heat. Neither system is 100% efficient at turning electricity into useful hot water. There are always losses. They're just being honest with their accounting.
The electronic components that create microwaves (magnetron, transformer etc.) are only 50-70% efficient at making microwaves the rest being lost to waste heat. In order for this device to be 96% efficient they must be capturing waste heat in the water through some sort of heat exchanger.
Whats the point then? A resistive element immersed in water converts nearly 100% (probably some light losses at the elements base) of the energy to heat in the water its immersed in.
So on one hand you have complicated expensive microwave system that still resistively heats the water in a much more complicated way losing 4% still to waste heat or you have a much more simple resistive heating system that probably does better.