Living in Electric Dreams

Posted on June 6th, 2012 by

Without precise energy consumption measurements, the cost and carbon savings reported by PC power management solutions can be wildly inaccurate. So, what drives an organization to adopt PC power management tools? Typically, it is the combined desire to reduce carbon footprint and generate cost savings across the business. Both of these goals are based on affecting the underlying energy consumption, so it is vitally important that you accurately measure energy consumption to have valid CO2 and cost savings numbers.

Calculate kWh accurately and the rest will follow

When reporting on consumption or savings, there are a number of key metrics an enterprise must be aware of. The three most critical are: the quantity of electricity used by its PCs, the cost of this electricity and finally, the CO2 emissions caused by the electricity its PCs are consuming.

To calculate how much electricity a fleet of corporate PCs is using, solutions that only use average consumption figures are not enough. For example, a low-energy PC might use as little as 25W while a high-performance workstation could use more than 300W. This is a considerable difference and makes the use of an average to calculate electricity consumption ill-advised and impractical not to mention inaccurate. To ensure accurate measurement, there must be an appreciation of the variable electricity consumption rates of different PC makes and models. This data should also be fed into the PC power management solution’s reporting console.

The cost of PC energy usage is calculated by multiplying the amount of energy used (in kilowatt-hours (kWh) by the price per kWh (the electricity tariff). Take a global organization for example. Different office locations will source electricity from different utility providers, which will therefore have different electricity tariffs. A global organization’s PC power management solution must support multi-location tariff-based reporting where a combination of two or more tariffs (a day rate and a night rate for example) may apply. A U.S. branch office might pay 10 cents per kilowatt hour while at a Canadian office, the tariff is 30 cents. As with energy consumption, many PC power management solutions tend to work with average tariffs for reporting purposes. Should an organization need these reports to demonstrate compliance with legislation or for corporate sustainability objectives, average amounts simply won’t suffice.

The CO2 emissions caused by electricity use are based on a carbon emissions factor provided by the electricity utility, which takes into account the mix of methods that were used to produce the electricity (e.g., coal fired power stations usually emit more carbon per kWh of electricity produced than natural gas fired power stations or wind power). To calculate the CO2 emitted, an organization must multiply the kWh of electricity used by the carbon emissions factor (e.g., 1.329 lbs. CO2/kWh). As kWh forms the base of this calculation and of the total cost, it is vital to have an accurate measurement.

Getting it right

The right PC power management solution will accurately record the time spent in each power state on the local machine down to the minute. The amount of energy consumed varies depending on this power state. In many cases, even when the machine is off, it will still be consuming energy. The solution needs to be able to record the power states locally on each machine so that it knows about every state transition and never misses any. Organizations need to be wary of agentless solutions that utilize remote polling as this will inaccurately report the time a state changes or even miss some states entirely.

Organizations need to make sure they have a way to record the time spent on, off, in hibernation and sleep modes, as well as if the screen, any additional monitors and hard disk are saving power. A strong PC power management solution would be able to take this information and report it back to the central database where it can then look up the make and model of the computer and the energy it consumes in each of those states. Organizations should look for products with a comprehensive database of desktops, laptops and monitors and, as a result, the ability to output the most accurate picture of energy consumption.

The end result will be a highly accurate report of the true kWh usage of every machine across the entire enterprise, allowing for precise calculations of the savings in cost and CO2 that an organization is making. If an enterprise is not measuring kWh accurately, then it is basing its savings calculations on a guess, thus living in an (electric) dream world.


The opinions expressed in this article are solely those of  the author Nick Milne-Home, president, 1E,  


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