Going ‘Green’ Saves Money

When I am asked to help districts save money or financially justify the paradigm shift to One to One computing, I suggest they audit their technology energy use. Shifting from traditional desktop PC’s to laptops, netbooks, or thin clients can save significant amounts of money, to say nothing of it being the environmentally correct thing to do.

A typical desktop computer uses between 65w-250w of electricity. A typical CRT monitor uses 80w and LCD 35w of electricity. You can get the actual amount of energy usage by checking the label on the specific device, or you can use a watt-meter to measure real energy consumption.

So, if we use 158w as an average for desktops and 58w as an average for monitors our total energy use is 216w per computer.

Let’s compute the energy cost of running just ONE computer for a typical school year.


1. The computer is in use 6hrs per day. (6hrs x 216w = 1296w)

2. The computer is left in power saver mode over night. (18hrs x 35w = 630w)

3. The computer is in use 200 days per year. (200 days x (1296w+630w) = 385,000w)

4. The computer is in power saver mode on weekends and holidays, approximately 100 days. (24hrs x 35w = 840w) x 100 days = 84,000w)

5. The computer uses no energy 65 days of the year.

Total yearly energy cost for ONE computer is 469,000w or 469 kilowatt hrs.

Estimated yearly cost for ONE computer @ .17 per kw hour = $80.

Energy cost for ONE computer over a (5) year lifespan = $400.

Total annual energy cost for ONE THOUSAND computers = $79,730.

Total energy cost of ONE THOUSAND computers over (5) years = $398,650.

Now, lets look at alternatives to the energy hungry desktop PC approach that is so prevalent in our schools today.

A laptop or netbook averages about 30w, most of it related to the display.

A thin client and display also averages about 30w.

Thus replacing a standard desktop with a laptop, netbook, or thin client device theoretically produces an 86% reduction in energy consumption.

Estimated yearly cost for ONE device @ .17 per kw hour = $11

(Savings =$69)

Energy cost of ONE device over a (5) year lifespan = $55

(Savings =$345)

Total annual energy cost of ONE THOUSAND computers = $11,000


Total energy cost of ONE THOUSAND computers over (5) years = $56,000


Even if we take the ‘best case’ desktop scenario: a 65w computer and 35w display, the energy savings for shifting to laptop, netbook, or thin client devices is 54% resulting in a savings of $227,230.

In One to One implementations, if students use battery power during the day and are required to charge their devices at home, the energy savings can be more than 95% and a cost savings of $378,717.

The yearly $68,530 savings in energy costs (ONE THOUSAND computers) can purchase:

An additional (228) netbooks, or thin clients per year. (@$300 per device)

Over (5) years a school can DOUBLE the number of devices available to students (1140) based on energy savings generated by switching to netbooks or thin clients.

If you are more interested in the traditional route you can purchase laptops and add an additional (86) devices per year (@$800 per laptop) and increase your network by (430) devices over (5) years.

Anyway you look at it there is a good case to be made to go “Green”.

It’s time to shift our technology energy paradigm.


Virtualization, Thin Clients, and Energy Consumption

In previous posts I documented a financial strategy that allows the average district to afford ubiquitous and/or one-to-one computing. This week I want to broaden the strategy to energy savings. It’s amazing what a significant savings replacing traditional ‘fat clients’ with ‘thin clients’ can be.

The University of Pennsylvania produced the energy graph below which shows the average PC drawing more than 100 watts during moderate use. This doesn’t include the monitor which on average can draw approximately 75 watts. So, for the sake of today’s post, let’s settle on 175 watts for the average energy use of a typical desktop used in our schools.


Below is another chart, from the Mr. Electricity blog, showing ranges of PC energy use.


The chart below, from Steve Greenburg, President of Thin Client Solutions, shows the average energy used by several models of WYSE Thin Clients. The 3630 model uses more energy because it has a built in monitor. The other energy readings are without monitors.


From the same report, notice that the amount of energy consumed by Thin Clients is significantly less compared to the traditional PC.


What kind of savings can we expect by implementing a Thin Client solution? Let’s look at a district with 1,000 computers.


1. 175 watts used by each computer.

2. Each computer in moderate use 6 hours per day; 185 days per year.

3. Computers left on overnight and during the summer use approximately 35 watts.

4. The Thin Client solution uses 6 watts plus 75 watts for the monitor.

5. A utility rate of $.14 per kilowatt hour

Using these assumptions, the total amount spent on energy for our 1,000 computers is $64,680.

Now, let’s do the same calculation with the Thin Client solution

The approximate savings by implementing Thin Clients for our 1,000 computer network is $29,291 per year; a 45% savings in energy costs.

The 5 year savings = $146,455

$146,455 can be used to purchase quite a few new $450 devices.

BTW, it’s not only cost effective; but the right thing to do for our environment


Note: Obviously, energy use can vary based on many equipment and usage factors. The savings shown here are illustrative only.