Sustainable Information Technology

Green IT in the Home: The Ultimate Guide

Green Home Graphic

Are you concerned about the impact your home computing has on the environment? Are you sure you’re following Green IT guidelines when you buy a new PC or mobile, tablet or laptop?

What about energy consumption as you use your PC, or what to do when you dispose of it?

Up until now, the Green IT movement has been focused on making sure that large and medium sized organisations use Information Technology more efficiently and in a more environmentally friendly way. Corporations use a lot of IT kit, so it’s vital that they use IT  responsibly.

But why Green IT only for companies? We can use all of the same techniques and lessons learned in business and industry to make improvements in the way we use IT as private individuals in the home and on mobile devices.

Environmentally, this is crucial. Carbon emissions from domestic use of IT by each of us may well be tiny, but when those emissions are multiplied by the ever growing number of global users of IT, the problem becomes significant. It’s not just energy use either. There are other factors to consider – which is where the IT Lifecycle comes in.

 The Green IT Life Cycle

If you think that being a Green IT user in the home is only about buying a more energy-efficient PC, laptop, smartphone or tablet, this article is for you. Just like major corporations, we need to take into account the whole of the Green IT life cycle, and base our buying (or not buying) on a much wider set of considerations. We can think about the Green IT lifecycle in terms of these categories:

  • Materials, Manufacture and Transport
  • Use of IT equipment
  • Disposal of the equipment

Materials, manufacture and transport

The carbon footprint of IT equipment is produced in two kinds of ways. The one that most people are aware of is the amount of energy consumed while the kit is in use.

The second source of carbon, other Green House Gases and environmentally unfriendly effects is referred to as embodied emissions. Materials have to be mined, transported, transformed into devices through manufacturing processes, transported again, used and disposed of. You need to take embodied emissions into account to really embrace Green IT.

All of these activities and the carbon emissions they produce are embodied in the IT devices we use. And for each one there is a price to be paid which is not always just about emissions but also other issues such as working conditions, landfill use and disposal of toxic substances.

Materials, manufacture and transport are all about the supply chain. We need to consider how the earth’s raw materials are transformed and transported to become the IT devices which we find it increasingly difficult to do without. In practical terms, we need to investigate the manufacturers and retailers who provide our equipment. Do they treat and pay their workers fairly? Are they environmentally responsible? Do they work with and for the communities they are a part of, or do they exploit the people and environment around them?

 Use of IT Equipment – 5 Green IT questions answered

There’s a lot we can do to minimise environmental impact when we use home or mobile computing devices.

How can I choose energy efficient laptops or PCs?

Firstly, laptops usually consume significantly less energy than PCs and are therefore cheaper to run and generate less emissions. There are various certification schemes that compare energy efficiency in IT equipment, and you should check those to see which manufacturers are producing the Greener devices. Depending on where you are in the world, there could be a more specific local certification scheme, but you can start with the following list of resources:

Energy Star Computer Finder

If you’re at all concerned about the environment, I think this quote from Energy Star shows just how important Green IT is:

“If all computers sold in the U.S. met ENERGY STAR requirements, the savings in energy costs would grow to $1.8 billion each year, reducing greenhouse gas emissions equivalent to those from more than 2 million vehicles.”

Energy Saving Trust – Recommended Computing Products

The Trust states that “around 12.2 million desktop computers in the UK, and around 17.3 million laptop computers. As the UK has around 26.5 million homes, domestic computers (desktops and laptops) now outnumber households.

Choosing an energy efficient desktop or laptop computer can have a real impact on reducing carbon dioxide (CO2) emissions.”


I haven’t personally used sust-it’s services yet but their site seems like a very powerful resource. They’ve put a huge amount of work into providing lists of equipment ranked by annual power consumption, and you see running costs based on energy tariffs in the UK, US and many European countries.

Do I need the biggest storage drive or most powerful processor?

More storage and processor power is quickly becoming redundant as cloud computing becomes cheaper and more convenient. There are huge amounts of free storage available with Dropbox, GoogleDrive and Amazon Cloud Drive.

There are also many free or very inexpensive applications in the cloud, such as Google Apps. We need to start thinking of our computers as gateways into the internet where we can store our files and run our programs.

Are there ways to save energy and do other good Green IT stuff as I use home PCs and laptops?

There are indeed!

Always switch off computers when not in use, or use sleep mode settings. All Energy Star recommended devices come with power usage controls such as sleep mode, so make sure you set these.  For example, on a Windows device, go to the control panel and search on ‘Power option’. You can choose or edit a power plan, change battery settings or when the computer sleeps, and when to turn off the display.

Just as in a huge datacentre, airflow in your study or other room where you have computing equipment is important. Good airflow will result in your computer’s cooling fans kicking in less frequently – thereby saving energy. This is especially important with desktop PCs.

Modern LCD monitor screens do not need screensavers. Running screensaver software actually consumes energy, so don’t use one unless you have an old-fashioned screen.

Also think about printing – do you need to do it, and if so, can you use recycled paper?   

When should I replace an old PC that may be energy inefficient?

Replace old PC

I wonder if it's time to replace my old PC?

As technology improves, newer computers tend to use less energy than older ones. But just regularly buying the latest computer – besides being an expensive strategy! – isn’t the answer. Don’t forget that when you buy any computer, you also buy its embedded emissions, not just its potential to be more efficient in operation. So a new computer has to be MUCH more energy efficient to justify replacing an older one if you want to follow Green IT practices.

Although it doesn’t take embedded emissions into account as far as I can see, there is a service by Sust-IT (again, I haven’t used the service, and have no connection with the company) that they claim helps you to decide on “Repair vs New”. You fill in a form describing your current kit, and they send you back advice. If anyone has used this service, please let me know how it worked out.

What about energy sources?

To take Green It in the home seriously, you have to consider not just how much electricity is being used, but whether the power is being generated from low-carbon sources. The answer will of course be relevant for all of your electricity consumption in the house.

There is no substitute for research in this area. Go to your supplier’s web site and examine their claims on renewable energy, then find some independent opinion on whether that supplier lives up to their promises.

How should I dispose of computing equipment?

The UK Government has some solid advice in this area, not all of which will apply in other coutries. Try here for similar advice in the USA.

In addition to what’s already been said about keeping your computers and mobile devices for longer, the advice boils down to this:

  • Make sure you wipe all of your personal information!
  • Freecycle: give and receive unwanted items for free Opens new window
  • Freegle: give and receive unwanted items for free Opens new window
  • Donate to charities: some specialist charities use your donated technology in developing countries
  • Make sure you wipe all of your personal information!
  • Find an electrical recycling site or contact your local council’s recycling team
  • “When you buy a new electrical item, ask the shop where you buy it how they will help you recycle the item you’re replacing. Under the Waste Electronic and Electrical Equipment (WEEE) Regulations, they must either:
    • accept in-store, free of charge an electronic item equivalent to the new item you’re buying
    • tell you where you can take the old item for recycling free of charge”

What else do you think should be added to our Green IT in the Home guide? Let us know!

What is the Cloud?

Back in the day, I worked as a network technician for one of Britain’s biggest companies. Whenever a new system came along, if the network architects had done their jobs properly, we would get a system diagram that explained how the network linked up people and computers and software. The diagrams looked something like this:

Pre-Internet Network Diagram

Pre-Internet Network Diagram

The Internet and the Cloud – Who Knew?

Then one day I woke up and the internet had happened. And suddenly I was presented with a network diagram that looked more like this:

Cloud Internet Diagram

Cloud Internet Diagram

At this point I went along to the network architect and had a brief conversation along these lines:

Me: What’s this cloud thing on the diagram?

Her: The internet.

Me: Why?

Her: So we can connect everything up more easily. The internet has lots of special computers like routers and switches that direct the communications between our computers and software and the people who use them.

Me: Is there anything else in the cloud?

Her: Not much. Yet.

Me: I think I’ll write a smog* about this. After I’ve listened to Tears for Fears on my room-sized ghetto blaster.
*Blogs didn’t exist then. I was predicting what they would be called once they were invented. I think you’ll find I was 50% right.

Today’s Cloud

So the origins of what we call the cloud today are in this diagramming technique. Back then, the cloud simply represented the internet. But the cloud and the way we use it have continued to develop over time.

The most obvious thing in the cloud is the web itself. In effect you are using a cloud service now as you read this smog blog. The words you are reading are encoded on a web page that sits on a web server (a computer dedicated to ‘serving’ web pages) which is connected to the internet. Nowadays we might say the web server sits in the cloud.

Just to complete the picture, you navigate your way through the cloud using a special set of communication protocols to convert the web page address (the string of characters in the address bar beginning with ‘www’ ) into an address that computers can understand.

So far so good.

But today, when people talk about the cloud, they are really talking about specific characteristics of the internet. A good marketing word was needed to quickly and easily summarise these characteristics, and ‘cloud’ is a pretty good marketing word.

The cloud – as the term is now being used – has come to mean a bunch of different things, all based upon the idea of running computers and / or their software on the internet (in the cloud) rather than on local PCs or servers or mainframe (very large) computers. Depending on who you are (a company, a private citizen) and what you are trying to achieve, the implications of the cloud and how you use it are far-reaching.

How companies use the cloud

Let’s imagine Acme Corporation, which is using cloud computing; and Zenith Corporation, which provides cloud computing services to Acme and other companies.

  • Acme workers access data, files and software programs from anywhere, as long as they have an internet connection. Not just on PCs, but on tablets and smartphones.
  • Acme’s data is stored on servers which are owned by Zenith and which sit in Zenith’s huge Data Centre.
  • The costs of purchasing and setting up storage devices is high and sometimes unpredictable. By having Zenith do this for them, Acme can lower their costs (they don’t need to own the servers or the skills needed to design and operate them). Because Zenith have well defined ‘price plans’ for their services, Acme can now also predict their costs more accurately.
  • Acme’s costs of developing or buying in software to run on its own computers are even higher. Zenith also has a SaaS proposition which Acme can use. SaaS is Software as a Service, which means that Acme can access software as and when it needs it. Again, Acme’s costs are potentially much lower and can be predicted more accurately. Two very well known examples of SaaS are Salesforce CRM and Google Apps.
  • The boss of Acme (which sells beds for cats) feels that when it comes to IT, the tail is wagging the dog. Too much time, effort and money are being put into IT, and not enough on selling cat beds. Zenith are the experts (thinks the Acme boss), so we’ll let them provide us with all of that clever IT stuff while we get down to the real business of pussy cat beds (this at least is the argument, though for many companies a complete outsource of IT of this type is an ambition rather than a reality).

How individuals use the cloud

Let’s take me as an example.

  • I use Google Drive and Dropbox to store files so that I can free up space on my laptop
  • Amazon’s Cloud Drive is where I store pictures and music
  • On the business / personal borderline, Mailchimp is where I go to send out formatted emails to lists of contacts – this is pure SaaS
The list of cloud apps is endless. I don’t use an iPhone, but if I did there would be many thousands of free and paid-for apps to access, and these are all in the “iCloud”.

Green IT and the Cloud

It is a green umbrella and it is under a cloudThe claim is that cloud computing is ‘green’. Green IT is all about using less energy (and cleaner sources of energy).

To an extent, cloud computing does this by being more efficient at storing data and programmes and by ensuring that computer capacity is just right (so that idle servers aren’t sitting around drawing electricity from the grid. One of the techniques for achieving this is virtualisation).

There is also the possibility that because of the scale of shared cloud computing services, less resources and energy are used. In other words, it is more environmentally friendly to have ten companies’ servers and software services in a single data centre than it is for each of those ten companies to have their own smaller data centres, servers, etc. This seems like good sense.

However, DCs use huge amounts of power, and data centre efficiency is a whole other other kettle of fish. Try what is PUE? for more on that subject.


What is PUE?

The aim of this post is to explain the background to Power Usage Effectiveness (PUE), what it is, what it’s used for and what people are saying about it.

The concept of ‘Green IT’  is a fairly new one. As technology changes and in turn transforms society, our understanding of what Green IT is and should be develops alongside it.  But the basic idea of Green IT is to make sustainable information technology a reality in businesses and in the home. One of the ways we can do that is to use metrics which help us understand and measure how efficient and sustainable IT actually is. PUE (Power Usage Effectiveness) is just such a metric.

Social Networks and the Cloud and eCommerce and Mobile Computing and… and… and…

PUE Power Usage Effectiveness But before we get into the specifics of what PUE is, let’s think about how these changes in technology are playing out in the real world. The global economy and society is driven by IT – in the huge expansion of social networks, eCommerce applications delivered from the cloud and the many flavours of mobile computing. In the developed economies we tend to relate these developments to cool stuff – people, places, games and applications. We equate celebrity tweeting, Silicon Valley (or Silicon Roundabout), viral marketing of Hollywood blockbusters, the latest iPad release and so on with what the internet is all about, and in some ways we’re right.

But many commentators have noted how the use of mobile ‘phones to find and share information is transforming day-to-day life for the poor in developing countries. This is an example of how the demand for information and connectivity will continue to grow exponentially for some years yet (see the United Nations Broadband Commission for Digital Development for some interesting background on global connectivity).

What these technologies have in common is their need to deliver information from data centres, the often immense buildings which house the servers and other computers which hold the information that’s presented to us through the web – in our offices and homes and on our PCs, ‘phones and tablets.

Those servers and computers need power: lots of power.

There are also other critical pieces of IT equipment that handle connectivity – such as switches, routers and load balancers. In the PUE equation, all of these pieces of kit taken together are what is referred to as IT Equipment Power.

IT’s all about Data Centres

But let’s think about this and what a modern data centre is like: potentially thousands of servers; potentially hundreds or thousands of network devices – switches, routers and so on… and all of this in a confined space. The amount of energy (the IT Equipment Power referred to above) being consumed is immense – but so is the heat being generated. So one of the first jobs of the data centre is to keep all of this equipment at acceptable operating temperatures. Like any other building, there are also other demands on the power supply. So the Total Facility Power part of the PUE metric includes items such as

  • IT Equipment Power (as discussed above)
  • Computer Room Air Conditioning (CRAC) Units and other kinds of cooling systems
  • Lighting
  • Power Distribution Units (PDUs)
  • Distribution losses
  • Generators
  • Uninterrupted Power Supply modules (UPS)

At last: the PUE Metric

Now that we know what is meant by IT Equipment Power and Total Facility Power we can start to understand what the PUE metric is really getting at.

The thinking behind the Power usage effectiveness (PUE) metric is that the efficiency of the data centre can be indicated by how much total facility power is needed in proportion to the power consumed by the IT Equipment alone. So if we had a scenario where total facility power was twice as much as IT equipment power alone, we would be running an inefficient data centre. The ideal PUE value is therefore 1.0 – a figure that would indicate that the ONLY power being used was that consumed by the IT equipment itself. Another way of stating this is that as the usage of power becomes more effective, the total facility power value and IT equipment power value will move closer to being equal.

The PUE metric was developed by The Green Grid. The inverse of PUE is DCiE, or Data Center infrastructure Efficiency.

Criticisms and drawbacks of PUE

Several criticisms have been levelled at PUE. These criticisms have to be seen in the wider context of Green IT, which is why I started this article with a description of what Green IT is trying to achieve. Data centres themselves, though big and complex – don’t exist in a vacuum. For starters, they are connected to power grids, and this is the source of the first criticism of the PUE metric:

Gripe 1: PUE doesn’t care about where data centres get their power from

Some electricity is generated with low carbon emissions. Other sources of power are ‘dirty’. PUE doesn’t discriminate between them. This was articulated in the 2012 Greenpeace report How Clean is Your Cloud? This is what Greenpeace said:

Some companies (are) inappropriately using metrics such as Power Usage Effectiveness (PUE) in place of meaningful metrics that would speak to the actual performance of their data center(s) in terms of computing resource or the natural resource being consumed in generating electricity.

In its defence, PUE wasn’t designed to measure total carbon emissions. To do so, it would be difficult to know where to start and where to stop. There is undoubtedly a huge role for measuring the carbon efficiency of electricity generation in the move to Greener IT, but PUE shouldn’t really be held accountable for not doing something it wasn’t designed to do.

What Greenpeace are doing here is really less about the usefulness of PUE, and more about putting pressure on the big data centre owners and operators such as Google, Microsoft, Apple and Amazon, so that they move towards ‘clean power’ more quickly. I applaud them for doing so.

Gripe 2: PUE can be deceptive and misleading

This is the most serious charge aimed at PUE. Again the Greenpeace report points out that:

in some circumstances, (PUE) penalizes better performance. For example, if a… manager identified servers in their data center that were not being used, and
elected to shut them off and create virtual servers, as shown in the table below, this could result in decrease in the power consumption rate (good) but an increase in the facility’s PUE (bad).

This is a serious objection indeed. In the real world though, it’s likely that turning off the servers and getting that 5mw saving would also produce more than a 5mw reduction in the total data centre power demand, which is the whole point about the PUE measurement. In other words, the switched-off servers would no longer require cooling, could be moved out of the DC server to a holding area and thus potentially improve air flow in the server room itself, be removed from the monitoring tools (a minimal saving, true) and possibly some other things I haven’t thought of, all of which could further reduce. total power demand.

Gripe 3: There are better measures than PUE

Again, in the same report Greenpeace encourage the use of another metric developed by The Green Grid: CUE, or Carbon Usage Effectiveness. This provides a carbon per kilowatt hour intensity measurement and has not yet been widely adopted by the industry. It’s great that Greenpeace are puching for more intelligent measures.


Like any metric, PUE has to be used in the right context. It would be great to have holistic measures of everything, but that isn’t practical. Used in the right hands there can still be a role for PUE, at least in exposing the most glaring inefficiencies in data centre management.


What is Green IT?

‘Green IT’ is a relatively new concept. I want to give a simple explanation of what Green IT is, but that turns out to be surprisingly tricky. By the end of this article we will have a reasonable working definition, but we have to recognise that the concept of Green IT is developing over time.

Green IT refers to two things which are in themselves changing rapidly. The first is our understanding of what is Green and what isn’t. The second is Information Technology, which is extending its scope, techniques and social and geographical presence on a daily basis.

Why define Green IT?

What is Green IT? This book helps answer the question

What is Green IT? This book helps answer the question


Why is it important to define Green IT so closely?

As we’ll see, current influential definitions are surprisingly wide apart in their accounts of what Green IT is. For example, if an individual or an organisation wants to reduce IT related carbon emissions and they are following the BCS definition, they will focus on different actions to someone who is following the Greenpeace understanding of Green IT.

So here is our first definition, courtesy of “Green IT for Sustainable Business Practice” by Mark G. O’Neill and published by BCS:


Green IT is a collection of strategic and tactical initiatives that directly reduces the carbon footprint of an organisation’s computing operation… However, Green IT is not just focused on reducing the impact of the ICT industry. It is also focused on using the services of ICT to help reduce the organisation’s overall carbon footprint.

There are some interesting things to note about this basic definition.

The first is that it’s all about organisations, not individuals. We have to question this, given the tide of information technologies currently sweeping the world in the form of mobile computing devices.

The second is that the ‘strategic and tactical initiatives’ have a different emphasis to what Greenpeace, for example, would see as the most important Green IT strategies. More on that soon.

Next, there is an emphasis on how ICT can itself be used to help to lower carbon emissions in other areas. For example, IT connectivity can cause people to travel less because they meet, make purchases, or carry out banking transactions via their computers.

Direct energy consumption vs. embodied emissions

Finally, although it isn’t apparent from the qoute above, the BCS / O’Neill view of Green IT emphasises the ICT life cycle as follows:

…it is crucial that we understand not only the environmental impact of the energy consumption of infrastructure, but also the environmental impact of its manufacture, transport, usage and disposal. It is therefore vital that we consider not only the GHG emissions associated with energy consumption, but also the embodied emissions.

Green IT ‘strategic and tactical initiatives’

So what are the Green IT activities we should be focusing on, according to BCS / O’Neill? They can be summarised as follows:

  • Change the structure and culture of organisations so that Green IT is high on the corporate agenda and aligned with Corporate Social Responsibility policies
  • Make sure individuals and teams are in place to carry out structured Green IT activities
  • Embed Green IT practices into IT processes (based on the ITIL framework)
  • When procuring IT infrastructure, adhere to standards (such as Energy Star and EPEAT) which emphasise both lower embodied emissions and lower power consumption
  • Manage data centre power efficiency, with an emphasis on PUE (Power Utilisation Efficiency)
  • Move towards virtualisation, cloud computing and software as a service
  • Encourage common-sense actions and tactics such as switching off computers, and duplex printing

The Greenpeace definition of Green IT

According to its April 2012 report “How Clean is Your Cloud?”,  Greenpeace has a straightforward definition of Green IT:

Green IT=
Energy Efficiency+
Renewable Energy

The Greenpeace view is that data centres, with their massive consumption of power, should be the main focus of Green IT initiatives.

…the source of electricity must be factored into a meaningful definition of “green IT”. Energy efficiency alone will, at best, slow the growth of the sector’s footprint… renewable energy needs to become the priority for IT companies as they rapidly expand their data center infrastructure.

Current measures such as PUE are misleading, they argue, because they do not question the source of electricity itself. There are other fundamental reasons why Greenpeace sees PUE ratings, which some companies use as a way to indicate how ‘green’ they are, as poor indicators of environmental performance. The drift of the argument is that IT companies need to use better metrics, and that some of these are already available.

Greenpeace ‘strategies and tactics’ for Green IT

Greenpeaces’s “pathway to a cleaner cloud” includes these key features:

  • Tapping renewable grid power
  • Power purchase agreements for renewable energy
  • Onsite renewable energy
  • Investment in renewable energy or offsetting local energy demand
  • Funding negawatts: local energy efficiency offsets
  • Clean energy advocacy by companies

So, what is Green IT?

Let’s put these approaches together.

Like the BCS / O’Neill version of Green IT, the Greenpeace report is focused on companies and for the most part leaves out individual users of IT. Of course the Greenpeace report is all about corporate cloud computing infrastructure, and the BCS publication is aimed at obtaining a Green IT professional qualification for use in the commercial world, so you wouldn’t expect them to be focusing on anything else.

Both approaches, I’m sure, recognise the need for the engagement of individuals in Green IT, but that isn’t an emphasis of either of these publications.

Bearing that in mind, here’s my working definition of Green IT:

Green IT is a set of practical measures designed to ensure that Information Technology is developed, delivered and used in a way that is environmentally friendly, sustainable and energy efficient.

These practical measures include:

For organisations and individuals:

  • Procure IT equipment and other infrastructure products based on both their power consumption efficiency and their embedded emissions. Use standards such as EPEAT and ENERGY STAR to help with buying decisions
  • Prolong the life of IT equipment, or when appropriate move to lower energy consumption products
  • Move to duplex printing as the default
  • Move to cloud computing and software as a service where appropriate
  • Turn off unused equipment
  • Recycle IT consumables

For organisations only

  • Put Green IT high on the agenda, with board representation
  • Structure the organisation to support Green IT initiatives
  • Change IT processes (such as Service Asset and Configuration Management) at the micro level to embed Green IT
  • Manage data centre power efficiency. Review metrics to ensure that they help to manage energy consumption reductions effectively
  • Move to server virtualisation, cloud computing and software as a service where appropriate
  • Implement server (and PC) power management
  • Use renewable and cleaner power sources

Have I missed anything? Let me know!