Home Power Audit: Overview and Conclusions

Posted in Tech on August 20th, 2009 by Andy
Baby polar bear says: "Thanks for cutting your carbon footprint!"

Baby polar bear says: "Thanks for cutting your carbon footprint!"

So what has been the result of conducting this audit? Let’s look back over some previous posts:

  • Introduction
    • We looked at power meters, and how to interpret the results.
  • Should I Unplug My Telly?
    • We discovered that leaving your gadgets on standby could be costing a lot of money
  • Battery-Powered Devices
    • It’s all about rechargeable batteries. There’s really no sane reason to be using disposables.
  • Green Computing
    • Some solutions: use a laptop/netbook/nettop, avoid torrenting with desktop PCs, use the power management features, and if you build your own, opt for efficient components.
  • Technological Solutions
    • Low energy lighbulbs, green electricity, home power meters, and micro power generation.

As a result of conducting this audit i’ve now got a better idea of where my electricity is going to waste. I’ve been able to make some simple changes in behaviour, combined with some automated methods, and have already cut my home power usage.

It’s a pretty simple process, it saves you money, and it helps fight climate change. So what are you waiting for?


Home Power Audit: Technological Solutions

Posted in Tech on August 16th, 2009 by Andy

There’s two main ways to save electricity: change your behaviour, or change your technology. Since most people are a bit lazy, what tech is there that can make being green easy?

Saves power, saves money, saves hassle. Sounds good!

Saves power, saves money, saves hassle. Sounds good!

Low-energy lightbulbs

Looking at the results of my own audit, it’s pretty easy to see which rooms are using low-energy lighting, and which aren’t. Installing low-energy bulbs can knock hundreds of watts off your energy use in one simple stroke. As an added bonus, low-energy bulbs last many times long than old-fashioned incandescent bulbs.

There are some limitations though. Most low-energy CFL bulbs can’t be used on a dimmer switch, and they have to be disposed of as electronics because they contain small amounts of heavy metals. As long as your local authorities have set up proper disposal systems for waste electrical goods that isn’t an issue environmentally

Switch to green energy

Probably the single greenest thing you can do, and one of the easiest. Switching to an electricity supplier that buys their energy from 100% renewable resources slashes your electrical carbon footprint to zero. Most green electricity is slightly more expensive than dirty power, but if you conduct your own power audit you should be able to easily find a way to economise that will pay for the difference.

This meter has been set to show cost of the power being used in real time

This meter has been set to show cost of the power being used in real time

Home power meters

Installing a real-time power usage meter on the wall can lead to real savings. It sounds too simple to work, but showing you how much juice you’re wasting at any time can be a great motivator. These devices are cheap and clip safely onto your existing wiring.

Home micro power generation

Depending on your budget and where you live, installing a small wind turbine, solar power generation or solar water heating can be economical. The exact details of break-even points for this kind of heavy-tech solution vary depending on a lot of factors, so it’s best to consult a supplier in your area.

Buy efficient gadgets

Start looking at power usage when you consider buying new toys. For large appliances this is now displayed prominently in the form of energy star ratings. Let the vendors know that energy ratings will influence your decision to buy.


Home Power Audit: Green Computing

Posted in Computers, Gadgets, Tech on August 12th, 2009 by Andy

Your computers are probably sucking a lot more power than you realise.

Take my audit results (PDF). My desktop PC can quite happily sit there sucking 100W, more than i’d be using to light the whole house some nights. Coupled with the fact that PCs are routinely left on for hours (or even continuously) and it adds up to a moderately shocking amount of wasteage.

Use a laptop

Laptops use a fraction of the power of desktops, and often have similar performance. From my audit results you can see that my laptop uses about 80% less power than my desktop.

Use a netbook or nettop

Don’t believe the hype from computer manufacturers. If (like most people) you spend most of your time on the computer using the internet, you don’t need a powerful desktop machine.

Netbooks are small super-efficient laptops designed for low-power use and long battery life. They’ll happily run a browser, office apps and internet goodies like Skype. As a bonus, most come preinstalled with Linux, so you won’t need to worry about viruses and malware.

The Asus Eeebox is so small you can mount it on the back of your monitor

The Asus Eeebox is so small you can mount it on the back of your monitor

A nettop is a similar animal, but for desktop use. Most desktop machines are hugely overpowered for browsing, but a nettop with a fast connection will give you 100% of the online experience without the overkill.

They’re built from laptop components and special efficient chipsets. You won’t be able to play the latest games on them, but if that doesn’t bother you, then they’re a really good option. As well as being more efficient than regular desktops they’re also quieter, cheaper and a lot smaller.

Examples include the Mac Mini, Asus EeeBox and the Linutop ( aka Viglen MPC-L)

Never torrent with your desktop

Torrents are great. The trouble is you need to leave the machine running for ages.


A NAS like the Qnap TS-209 will save power and money while protecting your data

In my case, leaving my desktop running 24/7 at 85W is not an attractive option. I’ve shifted all my torrent work over to a small efficient home file server from Qnap. Their range of home NAS (Network Attached Storage) devices will store all your movies and music on your home network, and download torrents at a measely 12W. Electricity costs for 24/7 use come to about £10.51 per year, compared to £70 for an 80W desktop machine. So the NAS totally pays for itself in electricity savings alone after about three years. Since I use one of the two-disk versions in a RAID1 setup, i’m also protected against data loss from hard drive failure, and the box is capable of a lot more. I’d recommend a similar device to anyone.

Use sleep/suspend

Modern PCs have more options than on and off. They can seamlessly move into low-powered standby states when they’re not being used.

Called sleep on Win/Mac and suspend on Linux, the machine shuts down all the hungry componants like processors, fans and hard drives, leaving your open apps in memory. At a moments notice they can be restarted. While in suspend my desktop only uses 1W more than it does when “off”!

I’d recommend setting your OS to suspend the machine whenever it’s idle for a few minutes. Most desktop keyboards and all laptops also have a hot key to suspend manually if you have to step away from the machine momentarily.

Use power-efficient components

If you build or modify your own machines then take a moment to look into efficient components.

Power supplies are a good place to start. Look for a model rated as “80Plus”, meaning it converts greater than 80% of the input power into usable power.

There are also some highly efficient CPUs on the market. For example the Athlon 4850e is a respectable 2.5GHz dual-core chip that’s rated at an amazing 45W, meaning it uses about half the power of similarly powerful CPUs.

Also, make sure your motherboard and CPU are compatible with the power-saving features built into modern chips. In a correctly matched motherboard a modern chip will reduce it’s voltage or even shut down whole cores depending on the demands on it. This can lead to large power savings.

Graphics cards are also a huge power consumer. In general, for machines that don’t do a lot of gaming, rendering or video work i’d suggest using the lowest-spec GPU that you can. For many people onboard graphics is perfectly usable.


It’s easy to be wasteful when it comes to powering your IT gear. But there’s also a ton of things you can do to give you a powerful, flexible setup that won’t eat the planet or your wallet.

Conducting an audit will show you where the problems are, and where a change in behaviour or hardware could bring about savings.


Home Power Audit: Battery-Powered Devices

Posted in Gadgets, Tech on July 24th, 2009 by Andy
We all have a lot of these little guys in our life

We all have a lot of these little guys in our life

In the first post of this home power audit series I described a way of measuring your power usage with a plug-in power meter. But what about electrical devices that don’t plug in?

We can get a good idea of home much power our battery devices use from rechargeable batteries. Using my plug-in meter I checked how much power it takes to recharge some flat AA batteries.

The bottom line:

Recharging 4xAA batteries took 0.13kWh of juice.

This usage would naturally include any overhead power loss from running the charger.

Should I use rechargeable or disposable batteries?

Rechargeables, always.

A rechargeable battery should be good for about 250 charges. At 0.13kWh for four batteries and 12.8p/kWh you’re looking at about 0.41p per battery per charge. Over the lifetime of the battery it’ll cost you a little over a £1 to recharge your £2 battery.

The equivalent 250 disposable batteries will cost you about £125. So it’s £3 vs £125. Per battery. Chargers cost about £10-20.

So apart from saving yourself a truckload of money you’ll keep a huge amount of highly toxic heavy metals out of the environment and you’ll save the hassle of continuously having to buy new batteries.

This is an absolute no-brainer, folks. If you haven’t already, buy a charger and start phasing your disposable batteries out when they run flat.


Home Power Audit: Should I unplug my telly?

Posted in Gadgets, Tech on July 21st, 2009 by Andy
This might be going a little overboard...

This might be going a little overboard...

By now, we’ve probably all heard that we should unplug or switch off any devices on standby around the house. The reward for doing so is that we get to continue having a planet to live on. Seems fair, but how true is it?

What’s the problem?

A lot of devices these days do actually consume power after they’ve been switched “off”. This can be seen from the results of my home power audit. Here’s some examples:

Off Idle Full
Flat panel TV 1.5W 1.5W 60W
14″ CRT TV 0W 3W 19.6W
Hifi 2.8W 26W 26W

So in fact it does look like we’re wasting some power. On all these devices “off” is taken as being switched off with the button on the front panel. Idle in the case of the tellys is standby mode, waiting for the remote to turn the screen on, and for the hifi is switched on but not playing anything.

How much is this costing me?

Even with them all switched “off”, we looking at wasting 4.3W. At 12.5p per kWh you’re talking about £4.70-ish of electricity per year. So hardly a big deal. However, if they were all left on idle we’d be looking at £33.40, which is starting to look like a real waste of money for just three devices. And i’m betting anyone that doesn’t live in a cave has a lot more than that.

What can I do about it?

  • Obviously, switch everything off whenever not in use.
  • If practical, switch off at the wall whenever you can.
  • Automate: buy timers that will switch off at the wall for you while you’re asleep or at work.

Tell me about these timers

They’re cheap. You can buy a plug-in timer for as little as £2. At that price it’ll pay for itself pretty quickly, and saves you the hassle of having to go around switching things off.

I sort my jumble of cables into things that have to be left on overnight (eg: router) and things that should be switched off (eg: TV) then put all the latter onto a timer that switches them on for a couple of hours in the morning and the evening. The timers have an override switch if you want to turn stuff on outside of these hours.

In my case I let the timer in my living room turn on for about 8 hours a day. That’s taken my standby wastage from 38.8W down to 28.5W, a saving of 27%. At that rate the timer pays for itself after 9 months, then everything after that is a saving. Best of all, I don’t have to actual do anything. Laziness + saving the world = win!

Savings will be even bigger on some of the more horrific standby power offenders. Mostly i’m thinking of PCs, more on that in a later post.

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Home Power Audit

Posted in Computers, Gadgets, Tech on July 18th, 2009 by Andy

Most of us only get a rough idea of how much electricity we use from how hard the power company stings us each month. But do you have any idea exactly what machines in your house are slurping all that juice? The only way to find out is conduct a home power audit, and the results can be pretty interesting.

Why bother?

  1. It’s easy. All you need is a plug-in power meter.
  2. Green is good. Conducting an audit will show you how you can reduce your carbon footprint.
  3. Money is good. You could be wasting a lot of cash each month.

Ok, how?

Plug-in meters are cheap and will pay for themselves in the savings you make

Plug-in meters are cheap and will pay for themselves in the savings you make

A plug-in meter does exactly what it sounds like. For my audit i’ve used a Brennenstuhl PM230 meter. You can pick one of these up for about £13 in the UK, and it does everything you need.  Another popular meter is the Kill-A-Watt, but they cost £10 more and do the same thing as the PM230.

These meters can do a lot of stuff, including calculating the actual cost of the power you use, but the main useful functions are showing watts being used by a device, and tracking usage over time in kWh.

Interpreting the results

First a bit of basic electrical theory. You’re probably aware that the power supply that comes out of the socket is rated in volts (either 230 or 110V AC, depending on what country you live in). But the measure of actual power consumption is the watt (W). Your power supplier bills you for the electricity you use in kilowatt-hours (kWh). Pretty simply: 1000W for one hour is 1kWh.

For most devices you’ll want to simply plug in your meter and note how many watts it sucks. For machines that run intermittently (such as fridges) you may want to take an average reading by leaving the meter plugged in for several hours. By dividing how many kWh by the number of hours you can get a rough average reading in watts to compare to other devices.

Important: Don’t forget to take readings of devices in their “off” and idle states. Many machines still suck juice when switched off, and anything that’s in a standby mode will certainly be slurping pennies out of your pocket the whole time.

Ok, let’s see some results!

Click here to download a PDF of my audit results.

Over the next few blogposts i’ll be taking a look at my results and discussing some of the issues, along with tips about how you can reduce your usage. Click on the tag home power audit on the right to see all the posts.

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