Mattia Butta, José Ignacio Márquez Camacho
Special thanks to Pavel Mlejnek for helping in measuring
Energy saving has recently become a very popular topic, in the last few years. Several pleas are frequently made for energy saving to population of industrialized countries. In the framework of such pleas, people is usually asked to switch the TV set off, when not used. This is supposed to make a family saving energy wasted by the TV in stand by mode. This suggestion is one of the most frequently repeated by many sources.
We want to understand if the stand-by mode of TV is really the most important issue for energy saving of a family.
We measured the power consumption of a TV and we estimated its energy consumption. Then, we compared it with the power consumption of other electrical appliances normally used in our houses, in order to easily quantify the energy wasted by TV in stand-by mode.
We used a ZES LMG 500 to measure the power consumption of all devices. Power has been measured every 0.5 seconds and the value stored on a flash disk. We later performed intgration of the power (when not constant) to get total energy consumption.
We took into account an old TV set produced by TESLA (found in a second hand shop). Unfortunately we do not have any additional data, about the model number.
However, we should mention that newer TVs employ techniques to spare energy in stand-by mode. Using an old TV we consider one of the worst possible case. The power consumption of the TV-set resulted to be 3.3 W.
We consider that in a normal family a TV could be watched around 4 hours per day , that is the idle time to be considered as stand-by is around 20 hours.
This results in 3.3 W*20 h= 66 Wh. This is the energy wasted every day by an old TV in a normal family if left in stand-by mode.
As most of the people are not able to quantify how much 66Wh are, we compare it with the normal usage of other appliances: we will mainly focus on the most energy demanding devices, considering the utilization which could be easily omitted by a normal family.
The considered vacuum cleaner consumes 792 W. If we consider a 30 minutes, as time necessary to properly clean a flat, we get a 792*0.5h= 396 Wh. This energy consumption corresponds to the energy absorbed by the TV set in 6 days.
This energy could be easily saved by using a broom instead of a vacuum cleaner.
We have measured the energy necessary to defrose a 400 g portion of lasagne using a microwave oven. As the microwave oven as switch-type behaviour (max power and no power consecutively applied with variable duty cycle, depending on the requested power), we simply integrated the data sampled every 0.5 s, in order to calculate the total power. In this case we used 300 Wh, to defrose the lasagne portion. We must mention this energy do not include the energy necessary to warm the food up. We simply consider the energy necessary to rise the food to food temperature.
Such energy corresponds to 4.5 days of TV left in stand-by mode. We can save this energy simply by leaving the food out of the freezer some hours, without using the microwave oven.
Ironing a shirt
We have measured the energy necessary to iron a man shirt, using a normal flatiron with built-in heater. As this kind of iron warm up rather quickly, we did not consider the energy consumption to warm up the device (which should be divided by all clothes ironed in that session). The energy necessary to iron a single shirt was 108 Wh, corresponding to 1.6 time the energy absorbed by TV in stand-by mode.
We can save this energy simply avoiding to change a shirt every single day.
We have considered the situation of a long hair person (namely one of the author) who need to dry his hair by using a hairdryer. The employed hairdryer has power consumption 1047 W, and the time requested to dry the hair was 6 minutes. The final energy consumption was therefore 1047 W * 0.1 h = 104.7 Wh, corresponding to 1.6 time the energy wasted by TV in stand-by mode. This energy consumption could be avoided by simply letting hair dry without using a hairdryer.
An electric heater is quite common in several families. It is usually employed to warm up the bathroom, when showering. This clearly makes the environment much more comfortable, but it also determines a huge energy consumption, which could be avoided by simply tolerating a lower temperature and therefore not using the heater.
We measured the power of a portable heater and it resulted 1681 W. If we consider that is can be used 20 minutes while being in bathroom, we derive 1681W *0.3h = 560 Wh, that is 8.5 days of TV in stand-by mode.
Finally, we identified five common behaviours which contribute to increase our energy consumption much more than the TV set in stand-by mode. If we want to save energy we should rather start reducing the usage of electrical appliances, which require more energy. We could estimate the cost of the TV stand-by in 66 Wh * 350 days (we consider a two weeks holiday per year) = 23 kWh per year. Considering the price for electrical energy in italy this corresponds to 23 kWh * 0.11479 Euro/kWh = 2.65 Euro. If we take into account that modern TV are designed in such a way that they consume less energy than our old TV used in this investigation, we realize that we end up in spending a couple of Euros per year. As a couple of coffees (or beers, depending on the country where we live).
We don’t make anything bad in turning the TV off, but it should be clear this won’t change much the total energy consumption of our family. We believe authorities should better focus on educating people to save energy in other appliances, which consume much more energy than the TV in stand-by mode.
We produced a movie where we try to explain in much more efficient way, this bunch of numbers. Values in the movie are slightly different: this is a popular video, whose goal is to make this issue understandable even for not scientific educated people, so we prefered to show “easy numbers” rather that being precise. The meaning of the research is the same, even if the numbers are slightly different.