# B KWh versus kW times Time

1. Mar 16, 2017

### FQVBSina

Say I have a 60W device.

I know running for one hour it uses 60 W x 3600 s = 216 kJ of energy.

Does that mean it uses 216 kWh of energy?

Or does kWh means 60 W x 1 hour = 60 kWh?

I am confused because the units in 60 kWh is not in their simplified terms.

More specifically, this pertains to a project that I am working on.
From experimental values, I found that with X kg/s of water flowing through the heat exchanger and some temperature increase, I can find the power of the heat exchanger in kW.
I would like to provide the values in BTU since that is just what people still use in the States.
I realized BTU is an energy unit, not power, and 1 kWh = 3412 BTU.
So I need to convert kW to kWh.

2. Mar 16, 2017

### davenn

you have a k in there that you shouldn't

60 W x 1 hour = 60 Wh

so going from what I wrote above

a 1kW heater running for 1 hour = 1kWh

3. Mar 16, 2017

### FQVBSina

Alright, thanks! I thought kWh is basically kJ. I guess kWh needs to convert by a factor of 3600 before it becomes kJ then.

4. Mar 16, 2017

### CWatters

Yes that's possible/correct.

I believe they actually use BTU/h (BTU per hour) but the "h" is sometimes omitted (bad practice).

So you just need to use..

1 kW = 3412 BTU/hr

5. Mar 17, 2017

### SlowThinker

One thing worth remembering: a Joule is a Wattsecond.
So 3600 J = 3600 W s = 1 W h = 0.001 kW h .