Is MW/hr a valid unit?

I saw a similar physics error on a sign in a local transit train a while back. I don't know what the writers mean, but energy per unit time squared is not a useful unit. If you know what the writer is talking about, and can look up real physics units elsewhere, you might be able to work out what he/she should have written.

 

i don't see why not, MW/hr is the rate of change in power, or the "acceleration" of energy. while power describes the amount of energy used per unit time, power/s would describe the amount of power used per unit time, or how the energy per unit time is changing. i don't think there's a distinction between a "real unit" and a "not real unit", the ones you usually see are the useful ones. for example the gravitational constant has units N*m^2/kg^2 or m^3/(s^2 * kg), I don't think theres such thing as a unit that is "not valid", maybe just not useful

 

There would be very specific cases where such a unit could make any sense. If I asked how is the power generating abilities of a country changing over time, someone could say that country X is increasing its power generating abilities by 35 GW/year.... which you could reduce down to MW/hour, although that would be kinda silly.

Your ideas of what the units mean are correct.

 

Where I saw the unit was on a sign trumpeting the fabulous amount of power available from the sun, quoting in MW/hr. This does not make sense. Yes, one could imagine a scenario where MW/hr is meaningful, with respect to the ability of a power plant to respond to rapidly changing demand, but in the context of the sign it's incorrect.

 

Another possibility is that they don't mean to use it as a unit. In one hour the sun emits 1.385×10^30 J of energy coresponding to 3.846×10^20 MW. Perhaps they meant MJ/h but meant to say that in one hour, this is how much power is produced by the sun

 

MW-Hr is a valid unit as a measure of energy produced or consumed, 1MW-Hr is 3600 MJ (Mega Joules). It's rather easier to picture 24 Kw-Hrs as a fan heater running all day rather then 86,400 KJ.

 

There is a lot of misconception, in the general public, on the distinction between energy and power. As you said, it doesn't make sense to say the power is ___ MW/hr. Whoever wrote that does not understand it, and we can only guess as to the actual meaning.

 

there is nothing invalid about MW/hr, but I don't think that it means much as a unit. I don't think it has many applications. MW-hr is a measure of energy.

 

What is the ramp rate of the reactor? 90 MW/hr. Usually it's expressed in percent full power per hour but MW/hr works as well.