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2013
Let us consider OSIsoft training facility located within OSIsoft’s offices in San Leandro, California.
The training facility has desktop PCs for 20 students, a desktop PC for the instructor, and several server class machines. The current facility first opened for customer classes in 1997. What savings or cost would be achieved by not upgrading the PCs and monitors of the training room? At one point in time, usual practice was to only upgrade the PCs every 4-5 years and upgrade the monitors only every second or third PC upgrade. The following use case suggests replacing both PCs and monitors every few years would pay for itself in energy savings alone.

Background – HVAC on weekday nights and during entire weekend were turned off for this room as part of a set-back, cost savings measure by the building management. During warmer months, each evening the room temperature would rise quickly to 85 degrees F and higher. On weekends, with the HVAC off from Friday afternoon until Monday morning, the temperature in the room would sometimes rise to 100 degrees F or more. The computers in the room had chronic problems with equipment failures until about 5 years ago. What happened 5 years ago?
  • Each student PC and the instructor’s PC had a 17 inch CRT display. These CRTs typically consumed 140-160 watts and ran 24x7. (546 BTU/hr) About 5 years ago these monitors were replaced with 17 inch flat screens of higher resolution. The new monitors typically consume 25-30 watts. (103 BTU/hr) CRTs turn a lot of their input power into heat. If we assume worst case and the input power all turns into heat, each of the new monitors produce 110 watts less heat.

Using a calculator found on Viewsonic’s website[1], we see the following:


The 20 student PC CRT monitors, the instructor's monitor, and a shared monitor for the server machines [2] in the room were costing OSIsoft about $5322 per year in electricity cost, just to operate the displays. That does not include the HVAC costs associated with removing heat from the classroom.


22 new flat screen monitors, which didn’t have “Energy Star” rating, are costing OSIsoft about $577 per year in electricity cost. If the new flat screen monitors had been purchased as “Energy Star” rated models, annual energy costs would be about $290.
  • Each student PC and the instructor’s PC were using about 265 watts. (910 BTU/hr[3]) The PCs were upgraded to newer, smaller units. The new PCs are using about 200 watts. (683 BTU/hr) If we assume the extra watts consumed were heat, the new PCs output only 75% of the heat the old PCs emitted.

With the old computers and monitors heat load into the classroom was significantly higher. PC
failures before upgrades were approximately twice what should have been expected based on manufacturer’s MTBF specifications. We could account for at least a portion of these failures due to environmental conditions of the classroom.

The sum of these upgrades resulted in about 600 fewer BTU/hr heat into the room per PC/monitor combination. It follows that reduction in HVAC demand during peak and off peak hours wound up being substantial, at least as measured by comfort level of personnel working in the classroom during off-peak hours. Failure rate of the new PCs has dropped to near zero annually. While it is warm in the classroom during weekend hours, working in the room is not unbearable. Combined electricity cost for PC/monitor savings is over $5000 per year. Due to the building infrastructure, it isn’t easy to guess at HVAC operational cost savings, but such savings are there.

Given that OSIsoft doesn’t usually replace the monitors at the same time PCs are upgraded, if we assume a payback period based on the PCs alone, PC operation energy cost savings wouldn’t pay for replacement cost of the PCs. However, if we add in the energy savings gained by replacement of both PCs and monitors, the replacement costs paid back in less than 3 years. Factoring in probable HVAC savings with PC/monitor operation energy savings, probable
payback period would be less than 2 years.


What are your potential savings in operational costs due to hardware upgrades you might implement?


[1] http://www.viewsoniceurope.com/uk/products/desktop-monitors/led-tco-calculator/



[2] http://www.docs.sony.com/release/CPD110GS.PDF


[3] http://downloads.dell.com/Manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-gx240_user's%20guide_en-us.pdf

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