Sunday, 5 June 2011

Carbon emissions from watching TV

Working out the carbon emissions/hour from watching TV is not so easy as you might think because there are a lot of components to consider, some of them very variable and hard to gauge. There are carbon emissions from the electricity to power the TV, from making the TV, making the program and, if you really want to be comprehensive, emissions from the spending choices of the TV stars who earn high salaries from appearing on the programs.

 ComponentFactors
Electricity to drive the TV: 70-500W between 1 or more persons (1) Depends on choice of TV and how many of you watch together
Emissions to make the TV 100-250kg (2) amortised over a few years and 10-50 hours watching/week for 1 or more people Depends on the choice of TV, then how long you keep the TV and how much you watch and how many of you watch together
TV signal transmission infrastructure and power Negligible given the number of viewers
Emissions to make the program Depends hugely on the type of program, especially on how much travel is involved, and then on how many people watch it
Emissions from film and TV stars spending their earnings ?

The more you watch, the less the embodied emissions in the TV matter and the more people watch a program the less it matters how much carbon is emitted in making the program. However, the more you watch the more electricity you use and perhaps also the more the TV stars are paid and spend.

This graph shows how just the first two components vary depending on how much you watch per week. I assume you keep the TV for five years and there are two people watching at all times. I show a smallish LCD TV which consumes 80W and has 100kg embodied CO2 emissions and also a much larger plasma TV which consumes 300W and has 220kg CO2 embodied emissions. For people who watch very little – only 7 hours per week – the embodied emissions may double the overall carbon but for TV addicts the embodied emissions make little difference.

As for the making of the program, the best figures I have found are for the making of Away We Go (2009), a romantic comedy directed by Sam Mendes. The film was made as a case study in reducing environmental impact so we can assume most films have higher emissions but for Away We Go the overall carbon emissions came to 975 tonnes CO2 (3), or 595 tonnes/hour (it is 98 minutes long). Judging by the gross takings about 1 million people have seen it in the cinema but according to the UK Film Council, 25/26 viewings of a film are on TV or DVD (4), so maybe this film will be watched 26 million times total. That brings the emissions to 25g/hour/person, which is the same again as the emissions from powering an 80W TV.

Nearly half the emissions from making this film came from air travel and most of the rest was from petrol and diesel for cars and trucks and generators for on-location filming. Programs made in a studio, reality TV and soaps which are shot mainly on one location will have much lower emissions. Nature programs like David Attenborough wildlife documentaries involve huge amounts of travel.

As for the emissions from the stars spending their salaries, we can use some data from my earlier post on avoiding the rebound effect. Suppose the salary bill for the leading stars on the film is £2 million  (the total budget for Away We Go was $17 million) and 26 million people watch it. That comes to 8p/viewer. If this was spent on beer in a pub, it would generate 9g  CO2 which is not much compared with the other emissions. However, 8p worth of a steak dinners would be more like 115g and 8p worth of plane trips more like 180g.

In all then, very roughly because there are a lot of assumptions here, watching a film on TV generates carbon emissions at the rate of
  • 20-80g/hour from the electricity to power the TV,
  • perhaps half as much again from the making the TV,
  • 25g/hour or more to make the film (much less for studio TV productions)
  • another 9-180g/hour from the stars spending their money.

Are you surprised? I was.

References
(1) NRDC TV Energy Efficiency Research
(2) How Bad are Bananas (Mike Berners-Lee)
(3) Away We Go Goes Green
(4) UK Film Council statistical yearbook

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