Just for the heck of it I used an online electricity calculator to see actual amounts comparing a 2012 Mac mini to a mac pro PSU. Not everyone can switch to a mini, but for many users the HD 4000 graphics in the mini are able to run Photoshop, Lightroom, CS6, etc. without problems. This isn't an endorsement saying the mini will be the perfect match for any user, but for those that it does work for, the benefits in the electrical bill are amazing. If your electricity provider charges .10 per Kwh (about the average in the U.S., some providers are half that and some are 1 1/2 times that), a Mac mini using 50 watts running at full blast 24 hours per day would cost $3.36 per month or $43.68 per year. Even if you use Apple's numbers of 85 watts for the mini, that's $5.71 per month or $74.26 per year, running 24/7. A Mac Pro using 980 watts (a Mac Pro PSU runs 980 watts, from what I've found online) at full power 24/7 would cost $65.86 per month or $856.13 per year. While neither is going to run full blast 24/7, and actual Kwh used is going to vary greatly by each individual user, that's still a startling comparison. Basically, the electricity alone saved per year would pay for the mini. Even if actual usage on the Mac Pro is half that, the electricity savings would pay for the mini in well under 2 years.