E=PT (Energy = Power * Time ) so see what Power is. It's Energy over Time.
P=IV (Power = Current * Voltage) FYI in case you need to calculate.
Using E=PT (which shows nicely what power is)
Power(Watts) = E/T = Energy(Joules) / Time(Seconds)
Power(Watts) is Joules per second.
There is such a thing as a watt hour and a kilowatt hour.
a watt hour is a unit of Energy, an alternative to Joules. Not a unit of power. It's how much Energy that is one watt(joule per second) over an hour. One watt hour is 3600 Joules. So, it's a bigger unit.
If you included in your post, the electricity cost, then somebody might be able to tell you. Otherwise perhaps somebody can tell you an electricity cost to use as an example
I suppose you could get an energy monitor and plug a drive in so it gets its power from the wall/mains socket. Or just use the rated power that the hard drive shows you. Then find out what the rate of charge is for electricity.
9Technically, power is the rate at which energy is transfered. A watt-hour is a measurement of energy: the amount of energy used in an hour at the rate of one watt is one watt-hour. Also note that many computer parts are labeled with the maximum power they may draw; actual power usage may be less at most times. – depquid – 2013-04-30T16:42:38.767
6Also, keep in mind that residential electricity is usually billed in kilowatt hours. Using 6 watts for 24 hours/day, 365 days/year will be about 52.5kWH. At my power company's current residential rates, that's about $4, so an SSD isn't going to pay for itself in energy costs anytime soon. – depquid – 2013-04-30T16:54:00.450
@depquid, right, but for laptops on batteries with ~50Wh capacity a 4 watt difference in power consumption may be quite a significant factor. – ulidtko – 2013-04-30T20:50:00.930
@ulidtko Yes, but the OP was about power cost savings, not battery depletion. I just realized that it says, "all our workstations," which implies a business environment. Since electricity for businesses may be billed for both power (demand) and energy used, and many rate plans are available, calculating business electricity costs for HDDs vs. SSDs is going to be much more complicated. – depquid – 2013-04-30T21:36:29.910