Wednesday, October 29, 2008

Energy Saving Tips -- TV

The bulk of electricity in many households is used by entertainment devices, e.g. TVs, computers, game consoles.

The easiest way to cut down electricity is not to use these devices at all. Easier said than done, so the second best thing is to use them less, which again is obvious, but also easier said than done, the last thing that you can do is use devices that are not so power hungry. Do not rush to the shops yet, it might be in your best interest to hang on to your old power hungry appliance, I'll explain below.

I would strongly suggest that you get a plug in electricity meter. I personally use a Brennenstuhl PM 230 Power and Energy Monitor, but there are other models


This can be one of the main drivers of electricity consumption. I can be quite smug here as I don't own a television, which enables me to save not only loads on electricity but £140 pounds a year on TV license fees. Enough of my smugness.

I do however have a 20" monitor. This uses 70-90W, depending on brightness and the amount of white displayed on the screen.

It's hard to do an apples to apples comparisons of TV technologies, but the image below can be taken as an average guide of what each type of technology uses and how much it would cost you yearly to run it (1 kWh @ 11.57p). I don't have exact model numbers for the TVs used, so I won't post them. The plasma TV was measured by a friend with a different power meter.

I can hear you say how the screen sizes are not the same, that is true but nigh on impossible to find a CRT that is 42".

While it is possible to calculate an average power usage per square cm, this can be misleading as there isn't a linear scaling.

The same friend that measured the plasma TV, also measured his 5.1 surround system that uses a whooping 130 W, which means that it uses the same amount of power as a 32" CRT TV.

Perhaps the most important figure is the stand by figure, which unfortunately I only have for the plasma TV, 30 W. While this might not sound like much, if you leave it on standby for 20 hours and use it for 4 every day you are looking at £76 of electricity in total, 25 of those pounds for the TV to be warming up air.

You might have heard many times on the media how you should not leave appliances in standby, I've just given you 25 reasons not to, unless you've got shares in your utility company.

There are also digital tuners and DVD/Blu-Ray Players. Unfortunately I don't have data for these. Sony quotes 8w for its DVP-NS39 model (dvd player) and 26 W for its BDP-S350 Blu-ray (Blu-Ray player). Standby figures are below 1W.

Humax quotes 10W in use, 5W in standy by for its F2-FOXT set top box (freeview digital tuner)

As you can see it pretty soon adds up, with a maximum power of 440W for watching freeview, 438 W watching DVDs and 456 W watching Blu-Ray discs on the plasma TV. While you are unlikely to watch 4 hours daily of blu-ray discs, it is not outrageous to think that you will use your 5.1 surround system while watching telly, were you to do this, you are looking at an extra £22, which brings your maximum consumption up to £98 and this is only to watch television.

A word of warning to people thinking about using a PS3 as a blu-ray player. The PS3 uses around 170 W, which is incidentally about as much power as it uses while idling PS3. Leave your PS3 idling 24/7 and you are looking at a whopping £172 a year, but I am getting ahead of myself

Sunday, October 26, 2008

Energy Saving Tips -- Lighting

I guess I should go over the basics when it comes to energy saving.

Incandescent lights are out. No ifs, no buts. If you want to save energy and money they have got to go. Light is the byproduct of heating up the tungsten coil, which is why they are so inefficient.
See a comparison below of how much it costs to run a 100 watt tungsten light bulb versus how much it costs to run an equivalent CFL. (kWh @ 11.57 pence)


At the time of writing Tesco quotes £2.94 for a 20 W CFL, which means that even with an average use of one hour it is better to use a CFL. If you then take into account that CFLs can last 6000-15000 hours vs 1000-2000 hours for incandescent light bulbs, then the total cost of ownership is so high for incandescent light bulbs that it is simply a no brainer to use CFLs.

At an average of 4 hours a day and assuming 8000 hours lifetime, a CFL will cost you:


£18.58 in electricity + £2.94 to buy the CFL

Assuming a lifetime of 2000 hours for incandescent lights, 8000 hours will cost you:


£92.91 in electricity + 99p to buy a pack of four incandescent light bulbs

CFLs are not the panacea. They do contain mercury, so it is advisable not use them where kids can knock them down and break them. They also emit more UV light. This is only a concern if you are sensitive to UV light AND are very close to the CFL. On a more mundane level they don't work with dimmer switches and can take time to switch on.

I can't think of any real reason for using dimmer switches, so it is not a problem for me. If you have a hallway that you need to light quickly I suggest using Halogen lights, while they are in essence incandescent lights they are brighter (in lm/W terms) and therefore need less energy than normal incandescent lights.

The SI unit of luminous flux is the lumen, unfortunately the lumen is not a common day unit and unlike the kilogram or the metre it is hard to have a feel for what a lumen actually is. You can get an idea by looking at the graph below, linked from Wikipedia, that shows a plot of Power vs Luminous Flux. An incandescent light bulb (red line) has approximately 1250 lm @ 100 W, if you look at a 100 W incandescent light you are looking at approximately 1250 lumens of luminous flux. I don't expect that you will need to be able to estimate luminous flux of light bulbs by looking at them, but this should give you an idea of what a lumen, or 1250 lumen look like.

In order to get 1250 lm with a CFL ( green line) it takes approximately 18 W. It takes a Halogen light bulb approximately 40 W to reach 1250 lm.

Friday, October 24, 2008

Measuring Energy (2)

Now it's time for the hard part: To measure energy usage regularly.

At the very least you should take meter readings once every quarter, this way you will be paying what you use rather than estimates. Feel free to lie to your utility company if you reckon that they will increase your monthly direct debit during the winter. This is essentially an interest free loan to your utility company. It's a shame that ofgem is such a gutless regulator. Again EbiCo has it right and doesn't provide discounts for receiving interest free loans from its customers (i.e. discounts for paying by direct debit).

You should aim to take meter readings every month. If you are really committed, like myself, you can take them every week. Make sure you take them at the same time each time (this is only relevant for weekly meter readings), as a couple of hours of heavy electricity or gas usage can skew your meter readings significantly.

Once you start taking readings, it is a good idea to put them in a spreadsheet. I personally use OpenOffice, it's free and can handle Micro$oft Office documents. The best idea is to create a plot like this one:

Energy Use

This way you can easily see how much energy you are using and with the plot above as a basis you can create a plot like the one below, which tells you how much it costs.

Energy cost

Tuesday, October 21, 2008

Measuring Energy

The first step in saving energy is to measure how much energy one uses. You might think that your utility company already does that, and you would be right, but I am talking about taking control here. If you were to ask yourself how much energy you use a year, it is possible that you know how much you paid for that energy but it is unlikely that you know how much energy you have used and this is what is important, the amount of energy that you use, if you don't know how much you use you'll never know how much energy you are saving. It seems unlikely that prices will be coming down soon or ever for that matter (I'll rant about that in another occasion), therefore any savings are going to have to be made by you, but before you make any savings you need to know how much energy you have used.

In a country like the UK, heating during winter is essential, particularly given the age of the housing stock, and air conditioning in the summer is a luxury. If you, like me, heat your house using gas (LNG) then your gas bill is going to be determined to a large extent by the weather. If you don't use gas, your electricity bill will be affected by the weather, but there is plenty of scope for reducing it.

At any rate, grab your old utility bills and get counting. Go back as far back as possible and look at the kWh figures. You want to compare like for like, therefore if you have made substantial changes to your house, e.g. doubled glazed windows, insulation or added an extension or conservatory, get your bills from after the change, that way you can measure exactly how much energy you use in your house as it is now. What you want to arrive is at a yearly usage figure for both electricity and gas. This will be your baseline energy use, your target as it were.

This is all well and good, but I appreciate that with utility companies relying more and more on estimates, the figure you arrive at might not be very accurate, that's true, you could try going back a couple of years and calculate the average energy use per year, that should iron out inaccuracies due to poor estimates.

Armed with this figure(s) (My figures below)

7500 kWh for gas
1900 kWh for electricity

You are ready to start saving.

It might be due to my scientific background but I like talking of energy use in kWh rather than how much it costs. This approach is more transparent as the savings or otherwise are not dependent on the whims of the utility companies. It is also fiendishly hard to calculate how much you are actually paying because of the many discounts and tariff tiers, kudos to EbiCo for having a simple tariff.

In order to simplify the calculation of how much energy you pay for during a year, I suggest you do the following:
  • Ignore discounts (Dual fuel, online, special rates, etc)
  • Calculate an average electricity and gas price tariff.
In order to calculate an average tariff one needs to calculate the relative weight of each tariff, so in my case my supplier (Scottish Power) charges anything above 4572 kWh p.a. at a lower rate, talk about madness, the more you use the less expensive it is, comparatively. Anyway back to my calculations:

4572/7500 ~ 0.61

So 60% is at the higher rate (4.860p per kWh), 40% at the lower rate (3.837p per kWh)

My average gas tariff = 0.6*4.860 + 0.4*3.837 = 4.497p per kWh

Doing the same for electricity I get an average rate of:

11.57p per kWh

(The cut-off for higher rate is 900 kWh p.a. for electricity)

Just bear in mind that the lower your energy use the higher your average rate will be. However, do not be deceived into thinking that you are not saving money, you are. Think about it this way, If I were to use 4000 kWh of gas a year, it would cost me £194.4, however if I were to use 5000 kWh I would pay £238.6.

So armed with these figures on to the energy saving sunset we ride

Sunday, October 19, 2008

Welcome to Energy Savers 'R' Us

I would like to say that I had an epiphany, that suddenly there was a break in the clouds, the sun rays hit me square in the face and I realized that I needed to start saving energy or perhaps an amazingly high energy bill arrived, a bill that I would be unable to pay without foregoing food and entertainment. In fact I can think of half a dozen different scenarios that are much more interesting that the truth, which is that, much like Germany in the thirties, this was a slow descent, not towards fascism but towards an understanding that I need not give my money to the utility companies unnecessarily. It was also a slow descent into the madness and obsession that only newly converted zealots are capable of.

Welcome to the obsesive world of energy saving (WES henceforth), next stop lower energy bills.

I am thirty one and I share a tiny flat with my girlfriend, who shall remain nameless. The flat is an old mid-terrace house divided up into three individual flats. We live in the ground floor flat. The flat has one bedroom and is around 40 square meters. The house was built around 1920 and it shows. Our kind landlord decided to install double glazed windows, for which we are very grateful as he did not increase the rent following such a leap into the twentieth century (thanks Olivier!). Unfortunately, the leap did not extend into insulation, which I can only presume that the house completely lacks as it appears completely unable to maintain any sort of reasonable temperature without the help of the central heating. The kitchen and the bathroom are on a sort of extension to the house, with only a roof on top. The flat on top does not extend above our kitchen and bathroom and I really wished it did, as the lack of insulation makes the kitchen and bathroom a nightmare of cold grey mornings, really unpleasant showers and terrible shaving sessions. As it happens, it is West facing, which means that all the misery the cold brings during Autumn/Winter is sometimes replaced by plastic melting heat, which unfortunately there isn't enough of. On the plus side it does remind me a bit of my grandmother's flat in Santa Cruz de Tenerife where one side of the flat was west facing and temperatures were easily above thirty all through the summer. Upon entry I would follow the ritual that all males in my family would go through: I would say hello, walk into the back room and take my t-shirt off. The problem with our flat is that unlike my grandmother's where the temperature was constant around the flat, here it is not. Candle wax goes soft in the kitchen but you need a jumper in the lounge, just like back home but in a forty square meter flat.

I think that what I was trying to say is that we can't actually change much in our flat, if we could I probably wouldn't be moaning in this Blog. I would have got insulation everywhere, changed the sole remaining light fixture not using low energy light bulbs and that probably would have been enough to reduce our heating bill enough not to care, but we can't and so I am moaning here.