Calculate your PUE Goals and Savings


Here’s a neat little calculator from 42U. In a single page, with the input of a few figures which are easily obtained, you can get a good overview of the savings achievable by aiming for a specific  Power Usage Effectiveness (PUE). The calculator asks for your existing PUE rating if known, and you can then adjust the target PUE. Input the cost of your electricity and your IT load in Kilowatts and off you go.




The resulting calculations tell you just how much money and CO2 you will save in the short and long term if you achieve your selected PUE goal (below).


If you are new to the world of Data Center Efficiency and energy saving, this is a great introduction. It doesn’t go into too much detail and there are some handy notes on the same page which will assist in the learning curve too. There’s even a video if you can’t be bothered to read – perfect for a Friday afternoon!

Another Data Center Metric Already? Cue CUE!

New reaches me from Dave Ohara’s great blog over at the Green Data Center Blog that the Green Grid have announced the CUE metric, Carbon Usage Effectiveness metric to help measure the carbon impact of IT equipment. Here’s the logic, which seems simple enough..


CUE = Total CO2 emissions caused by the Total Data Center Energy

                                             IT Equipment Energy


The carbon emissions divided by IT load. This provides a ratio of kg/CO2/kWHr where the best possible result is 0.  Fair enough? You should be at or near zero for example if you are using 100% renewable energy.

But is CUE a PUE too far? Mr Ohara seems to think so and I tend to agree, but for different reasons. As Dave states in his piece:

I think this is a metric that will not be popular.  Why? Because what is really important to many people is the total number of metric tons of CO2.  That’s an easy number for people to understand. PUE is an easy metric for people to grasp as the closer to 1.0 the better.  PUE is discussed much more than DCiE.

I actually think that the objections will be much more simple than that. Given that the Green Grid are also unleashing WUE (Water Usage Effectiveness) isn’t it just the case that most Data Center managers will be too busy to cope with all of these new metrics? And surely it just creates more margin for some companies to ‘fudge’ the figures if they so choose.

I think that it would be much easier to have a single Data Center metric that calculated the overall performance on all fronts. These days we seem to be faced with ever increasing amounts of red tape and reporting requirements, and although I think that the Green Grid is doing a fantastic job in enabling the industry to create some sort of understandable  reporting, I feel that these new metrics may be facing a cool reception.

Dave Ohara’s post can be viewed in full here:

The Data Center of the Future

As time goes on, data centers are moving more and more towards green technologies in an effort to become as efficient and carbon neutral as possible. Ultimately however, we are going to reach a critical point where green technology is no longer able to meet the electrical and infrastructure demands of a modern data center and I honestly believe we are already close. Google has already done the almost impossible; an average PUE of just 1.2 across its facilities with its sights firmly set on 1.1 in the near future. How they achieved this is detailed in the article ‘How low can you go?‘. In short, this means that for every watt of grid electricity used to power the IT equipment, only 0.2 watts is required to run the facility and the closer we get to 1.0 (or zero watts required to run the facility), the more difficult things become.

Despite the fact that the likes of Google and Facebook are seemingly making monthly breakthroughs in data center efficiency, there is going to come a point where we simply cannot go any lower due to the fact that data centers (in most cases) need some sort of infrastructure in addition to the IT equipment. This can range from building management systems, fans and chillers, down to lighting and running water. All of these represent an overhead. The biggest overhead today remains cooling. Regardless of how you are keeping your servers cool; free-air, sea water or old fashioned air conditioners, you still need power to run the cooling system and for the most part, that power comes straight from the grid. Not necessarily for long though.

University of Arizona physicists have discovered a new way of turning waste heat into electrical power. Using a theoretical model of a ‘molecular thermoelectric device’, it may be possible to re-use probably the biggest emission from most data centers today; hot air. According to Justin Bergfield, a doctoral candidate in the UA College of Optical Sciences and lead author of an article in the scientific journal, ACS Nano, “Thermoelectricity makes it possible to cleanly convert heat directly into electrical energy in a device with no moving parts,”. The technology works in a similar way to how noise-cancelling headphones are able to reduce background noise; a process called ‘quantum interference’ where two opposing but equal waves cancel each other out. In this case, the way in which the device (a sandwich of two electrodes with a molecular ‘forest’ filling) works is by encouraging the buildup of voltage between the two electrodes when quantum interference occurs and a heat source is present.

The technology is currently only in the theoretical stage but has the potential to increase efficiency across a wide-range of applications including manufacturing and automotive. It also represents a real opportunity to dramatically increase the efficiency of data centers where these devices would be used to capture the hot exhaust from the servers and covert it to energy to power the IT load. This could be exploited to a point where a data center could exist ‘off the grid’ or even further where it is able to provide energy back to the grid which would be especially beneficial in particularly power stretched areas such as New York City which are running over capacity.

Clearly at this point, the technology is largely a pipe-dream but it is extremely encouraging to see that research such as this provides us real hope for the future…

New Green Grid report consolidates PUE reporting progress

As I've stated before, sometimes there just seems to be too many standards out there. So hats off to the Green Grid who have got together with some of the key players in the field of measuring Data Center efficiency to produce a new report. Aiming to simplify the complex task of measuring PUE in the Data Center, Green Grid has worked with 7×24 Exchange, ASHRAE, Silicon Valley Leadership Group, U.S. Department of Energy Save Energy Now Program, U.S. Environmental Protection Agency’s ENERGY STAR Program, United States Green Building Council, and Uptime Institute. The new report, entitled “Recommendations for Measuring and Reporting Overall Data Center Efficiency – Version 1 – Measuring PUE at Dedicated Data Centers,” contains recommendations from all of the above organisations.

Generally speaking the report does the following:

Provides guidance on how to calculate PUE from weighted energy types, based on source energy
Outlines four recommended measurement categories for PUE, as a subset of The Green Grid’s measurement methods
Provides guidance for renewable energy sources, combined heat and power plants, and reuse of data center energy

Simple, effective, and a good start. I like the way that the Green Grid work to get stuff released and straight onto the next version – which in this case will cover mixed use buildings alongside the dedicated Data Centers covered in this version 1 report.

Download the full report here

Read the press release here




Raising the bar on Data Center energy efficiency

There’s nothing like a bit of competition get folks behind a good cause. The PUE standard had given data center designers and managers a defined figure to aim for and companies are now proud to publish  their PUE for the world (or not)  to see just how much energy/money/time they are saving.

As Andy Dominey says in yesterday’s post – the new ebay facility in Utah raises the bar in terms of energy efficiency, achieving an estimated PUE of just 1.4. So every Watt of energy used by servers or storage, only requires a total data center input of 1.4 watts. Very efficient. However,there's always someone who is aiming that little bit higher..

Cambridge Elean Data Campus – A Vision of the Future?

A UK company, BNB Developments, is planning to build a data center that they claim will have a PUE of less than 1. Huh? As they say on their website, there's no such thing as a Green data center, just greener..

The key to the efficiency of the solution is that the site just happens to have it’s own CHP Power Station. CHP? Well that’s Combined Heat and Power – a type of power station that’s been around for quite some time.

CHP 101

Energy isn't just wasted in the places that we finally use it; most of the waste in our electricity system happens before it even reaches our homes and businesses. Conventional power stations throw away enough heat as is needed to provide hot water and heating for every building here in the UK. How does this happen? Well, generating electricity by burning stuff like gas or coal for example produces huge amounts of 'waste' heat, which is simply thrown away by our power stations – for example, as steam up the cooling towers. Outrageous!

On average, our large, centralized power stations throw away two thirds of the energy they generate.

If power stations can be sited close to where heat is needed – say, near towns and villages or on industrial sites like Elean at Cambridge – then this heat can be captured and supplied to homes and businesses or used in industrial processes such as data center cooling. The heat capture technology exists and is actually well established in countries like Denmark and the Netherlands.

Here's how these guys aim to run the data center using CHP:

As you can see from this neat flow diagram, at the 700,000 sq ft Elean site near Cambridge, they are planning to use power from the existing CHP site, along with other energy saving technologies. This, they claim will result in a negative PUE. It uses some other cool technologies such as Absorption Cooling but that’s not unusual, it’s the onsite power source that’s key. All that heat that is usually wasted by power generators is re-harnessed and used to power the cooling facility. Crucially it should also exempt them from a chunk of tax in the form of the UK CRC Levvy so the financials stack up nicely too. Put it this way, if I had a truck load of servers with no home I would be heading their way. So maybe there's no such thing as a green datacenter, but if all of the servers in this facility were running NightWatchman Server Edition, it's hard to see just how you could make it any greener!

Check out the full story at


Global Data Center efficiency standard agreed.. almost

Standards can be a good thing, especially in IT (think USB, Firewire etc). Standards for measurement are great too, such as the Metric system which is used by most of the known world. Sorry couldn't resist that one America…

What is more relevant and also very imporant to us folks here at 1E is a standard for measuring Data Center Efficiency, which is just one of the things we're about. Fortuitously enough then, that news reaches me today via the global telegraph , that good sense has prevailed in the world of Data Center metrics in the form of an agreed global standard in this field. Almost.

The Green Grid has announced that agreement has been reached with various agencies  including the U.S. Department of Energy’s Save Now and Federal Energy Management Programs, U.S. Environmental Protection Agency’s ENERGY STAR Program, European Commission JRC Code of Conduct, Japan’s Ministry of Economy, Trade and Industry, Japan’s Green IT Promotion Council, and The Green Grid.

These participants have agreed on the use of Power Usage Effectiveness (PUE) as the preferred energy efficiency metric. PUE as a measurement metric has been around for a while but hopefully this agreement will see the metric go global.

This is important so that Data Centers of all shapes, sizes and nationality can be measured with the same set of rules, and it will also help to quantify the effectiveness of so called 'Green IT' initiatives with a recognised standard. In plain English, that means the CFO's may be a little happier about paying for it!

One important entry in the agreement, which I feel has been a tad unreported, is in the following paragraph of the document.

Desired Outcomes:
Effective energy efficiency metrics that:
1. Measure the actual IT work output of the data center compared to actual energy consumption. It is of note that in the process to define IT work output, the following interim measurements are being defined and / or validated:
a. IT – Measure the potential IT work output compared to expected energy consumption; and measure operational utilization of IT equipment

b. Data center facility and infrastructure – Measure the data center infrastructure efficiency (PUE)

So, as you can see I've highlighted the bit that excites me – just in case you missed it. This is what we've been trying to get over to people here at 1E for years, and that is the fact that it's all very well measuring the amount of energy that comes into the data center, and you can even measure things at the individual rack or UPS level, but to achieve true efficiency you need to monitor individual servers to see just what they are doing. Just because a server is on, well, it don't mean a thing.

In the next paragraph of the agreement, it states:

Guiding Principles
The collective groups are in agreement on the following guiding principles, as an interim step toward the desired outcomes (1. b.). It is recommended that data centers begin to measure PUE according to these principles:
 - Power Usage Effectiveness (PUE) using source energy is the preferred energy efficiency metric. PUE is a measurement of the total energy of the data center divided by the IT energy consumption
 -  The industry should improve the IT measurement capabilities to ultimately enable taking the measurement directly at the IT load (e.g. servers). At a minimum IT energy measurements should be measured at the output of the UPS
 - For a dedicated data center, total energy measurement should include all energy sources at the point of utility handoff. For data centers in larger buildings, total energy should include all cooling, lighting, and support infrastructure, in addition to IT load

So what they are saying here, is that in order to make your efficiency measurement as accurate as possible, you need to be monitoring your servers. Which is exactly why we introduced the concept of Useful Work™.

Using NightWatchman Server Edition you can monitor the exact metrics that this agreement is talking about, and integrate the results into your overall efficiency stats. Our monitoring capability in NWSE tells you exactly what a server is doing and when. For instance it can highlight when backups are running (Useful Work), or when a rogue application is chewing up the CPU and/or disk (Really Not Useful Work). Having identified a potential slacker server you can then implement our Drowsy Mode which is where the real savings start. BTW Really Not Useful Work is something I just made up but I quite like it and may submit it to the Green Grid for the next draft – what do you think?

In summary, I think that this agreement signifies a great leap forward in Data Center efficiency measurement. China and India have yet to get involved but I'm sure it's just a matter of time, and then we will at least have a chance to implement true global energy savings.

Useful Work Whitepaper

NightWatchman Server Edition Homepage

The Agreement in full (Green Grid)