Electrical requirements for tankless water heater

[sam E]

Now I'm wondering how long it would take that 15 watt water heater to heat enough water for a bath.

Probably forever, since it cools off faster than it heats. 0% efficiency.

[makolber]

assuming your delt T is in F degrees I get 19.8 kW

using 3.785 kg per gallon and a specific heat of 4.187 J/g K

it is interesting at $0.15 per kW hour it costs about 5 cents a minute to take a shower.

also a 45 deg F rise is a pretty cold shower, need more like 70 F rise, 50 to 120...no?

Mark

[Tony Hwang]

Hi,

1 BTU/hr is ~0.3W