We have a Sky+ satellite unit with integral hard disk recorder. In the UK this is known as a Sky+ box. The unit can be programmed to easily record programmes 24 hours per day and record complete series at a repeating time. It has lots of features, including OnDemand services where a wide range of channels are recorded on the off chance you might want to watch them. My specific Model Sky + HD unit is made by Amstrad
We also have a 46" Samsung LED TV which is hooked up to the Sky+ unit .
I use a CurrentCost household energy monitor, which is hooked up to the internet via a unit called a netsmart, also from CurrentCost (see my other post on currentcost). I can see on a web page a graph of my household energy consumption in close to real time. A 3rd type of device from CurrentCost is the Individual Alliance Monitor (IAM) which is a unit which plugs into the mains socket and an individual appliance plugs into it. It enables me to record and chart the consumption of any single device i.e the TV. I have two of these IAM devices which separately get recorded via the netsmart and so I can measure the energy consumption and patterns of consumption over time.I move them around to try to understand the patterns of consumption of different appliances i.e fridges , computers, fridges etc. It keeps me out of trouble.
Recently I moved the IAMs and connected them to the Sky+ unit and the Samsung TV, really just to see actually how much energy a fairly modern TV + hard disk recorder would consume.
Both devices are never turned off at the wall. The Sky+ unit has to stay on in order to record programmes throughout the day based on our families choices - that's what hard disk recorders do. The TV is turned off via the remote, but the wall socket is hidden away and inconvenient to disconnect.
I'm often hearing about the "evils" of standby mode and wanted to test to see if this is the case. I know you can buy so-called "Green" mains multi-way adapters which enable you to turn things off absolutely, even when hidden away using a master switch or remote. Trouble is that disk recorders need to be always on, or risk missing a programme set to record, and my TV mains socket was inaccessible. It has no electro-mechanical switch, just a power off mode on the remote which leaves a red LED glowing.
In this chart you can see a red line indicating the power consumption of the Sky+ unit and the purple line indicating the power consumption of the Samsung LED TV. This was captured after I had set the Sky+ units ECO standby mode and you can clearly see the period of minimal consumption
After a few days I had built up a set of charts from the IAM's which were quite revealing :
1) The Samsung LED TV used 100watts when in use. When in standby i.e turned off via the remote it used no measurable power or rather registered 0 on the IAM device, effectively zero consumption.
2) The Sky+ HD unit varied from 15 watts to 25 watts, over the day, depending on function. Standby mode (amber light) instigated from the remote power button registered 15 watts. Watching TV live this goes up to around 20 watts and 25 when the hard disk is working i.e recording or playing an existing recording. The more it has to do , the more power it consumes. fair enough.
So, in an extreme case, if the TV is left on for 24 hours, then the household will have consumed 100 watts * 24 hours = 2400 watts or 2.4 Units of electricity which would cost 34.8p.
Realistically if the household watched the TV for 4 hours , this would be 400 watts or .4 of a Unit. Which equates to 5.8p
The SKY+ Unit would consume between 15 * 24 = 360 watts per day for a day of no recording or use, through to an upper limit of 25 * 24 = 600 watts or 0.6 units per day which equates to 5.22p minimum to 8.7p per day if in continuous use
At time of writing the average price of a unit (kWh) of electricity in the UK is 14.5 p
I was a little surprised by how little energy both devices used. The Sky+ unit has many of the characteristics of a PC i.e a mother board, a hard drive etc..
I was interested to see if I could improve their performance using the provided configuration settings.
1) The TV. The Samsung TV has a very wide range of configurable settings via the remote controls .
via the Green Menu button -> Picture -> ECO solution. Within ECO solution I could set two optional settings , Auto-brightness which adjusts the screen brightness based on background light conditions i.e brighter when the room is brighter, darker when the room is darker. I could also set the ECO Mode setting itself to be low, medium or high i.e the total amount of brightness cut. I set it to low i.e. a small brightness cut, and set the Auto-brightness to auto.
Via the IAM chart, this showed a drop from 100 watts down to between 60-70 watts. Some fluctuation over the day which I put down to salient light conditions. However this is a respectable 30watts saving per hour, which is the same as swapping a 40 watt conventional bulb for a low energy equivalent. Experimenting further, setting the high ECO setting took the power consumption down to 45 watts, so a 55 watts saving per hour, though this varied with the light i.e more savings in the evening or when the room was darker.
I found the high mode rather grainy and settled on the light ECO setting which didn't appreciably affect the picture .
2) the Sky+ unit.
Two other things I set were
- Services -> Customise . I disabled both Pushed On Demand and On Demand Downloads. I do not need the unit to speculatively record programmes on my behalf.
- From the Setup option on the top of the Sky menu under Picture, I set the SCART control setting to off. I don't know if this saves energy but as the TV only uses the HDMI connection, I figured disabling SCART could only be a good thing.
After a few days monitoring of the Sky+ Unit, I could see that between certain hours at night the unit would sometimes power down completely, consuming no detectable power. Typically this was between 3:30 and 6 am, so 2.5 Hours when the unit was not using 25 or even 15 watts. on some days this mode does not engage as I assume this is where a recording falls within this period.
A further adjustment would be to double check that all the Scheduled recordings you are making are needed, as there is a knock on power implication to recording especially during the night power-down period. Hence setting the ECO standby mode has a potential saving of 2.5hours * 15 watts which is 37.5 watts over 24 hour period .
These savings are small, as if I watch 4 hours per day of TV I'm saving 120 watts from the TV settings, and possibly a further 37.5 watts from the Sky using ECO standby if no planned recordings fall during the night period. So that's around 160watts over a 24 hour period, which is 2.33p.
Over the year that is 58.4 KwH which I believe equates to approx 30 Kg of CO2 ** or �8.46, assuming 14.5p per unit cost. These appliances use reasonably low amounts of power . However the savings cost me just a few minutes of changing a few settings on my TV and Sky+ box , and save me a bit of money over the year and help reduce my CO2 footprint, albeit by a pretty small amount. If everyone did it , it could be significant
**Calculating the CO2 impact of electricity savings is hard as the precise amount of CO2 per KwH or electricity produced varies with the mix of generating technology on-line supplying to the National Grid. An assumption of 0.5 Kg of CO2 per KwH has been used and is in line with Government approved figures
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