Where does all the power go?

Ever wondered how much of your electricity bill goes on charging your laptop, or whether your TV is a bigger drain on your wallet than your kettle? I have…

A good basis to use in answering that question is the Annual ‘Energy Consumption in the UK’ report by DECC. Using their data on household electricity consumption, I’ve plotted a short history of UK electricity use by appliance. I’ve tried to aggregate similar devices together to create 6 categories: lighting, refrigeration, washing & drying, consumer electronics (TVs, consoles, device chargers), computing (desktops, laptops, monitors, printers) and cooking. It’s also important to note that this data is a total for all households in the UK, and is not taken on a per device basis.

The biggest individual energy guzzling devices today are TVs, refrigerators, halogen bulbs and power supply units (including chargers).

Some of this information isn’t surprising- refrigeration is notoriously expensive in physical terms, as it involves reversing a thermodynamic heat engine, in effect using energy to ‘suck’ the heat out of the colder compartment. Halogen bulbs are also commonly known as a large energy drain, due to their ubiquity and relatively low efficiency. Energy efficiency of both refrigeration and lighting have seen significant advances in the past few decades, and the relative drain on household energy of such devices reflects this.

I am, however, puzzled to see TVs on the list. The new generation of LED TVs and the advances in energy efficiency in electronics gave me the impression that these devices were far greener than their predecessors. In fact, the electricity used by TVs doubled between 1970 and 2000, and has almost tripled by 2012. I imagine this means that far more households have TVs now and that an increasing number of households own several. Even so, it is difficult to see why efficiency technology has not slowed the rate of growth of the electricity needs of televisions.

Laptops form a surprisingly small part of household electricity use, and power supply units (PSUs) and chargers appear to constitute a much larger energy drain. Perhaps the proliferation of smartphones and tablet PCs has something to do with this; the sheer number of devices that need charging may be the reason for the large increase in PSU consumption over the last few decades.

What can we take away from these statistics? On the surface, they hold few new suggestions in terms of how we should behave in order to save energy. It is common knowledge that one should boil as little water as possible in electric kettles, switch off devices and lights when they aren’t being used and purchase energy-saving devices instead of more power-hungry alternatives. However, these numbers do identify a large potential saving in energy consumption by switching to more efficient lighting methods and a significant rise in energy consumption by TVs and PSUs. The bottom line? Unplugging those idle device chargers won’t save the world from climate change, but it certainly could help.

This blog is written by Neeraj Oak, Cabot Institute.

Neeraj Oak

Converting probabilities between time-intervals

This is the first in an irregular sequence of snippets about some of the slightly more technical aspects of uncertainty and risk assessment. If you have a slightly more technical question, then please email me and I will try to answer it with a snippet. Suppose that an event has a probability of 0.015 (or 1.5%) of happening at least once in the next five years. Then the probability of the event happening at least once in the next year is 0.015 / 5 = 0.003 (or 0.3%), and the probability of it happening at least once in the next 20 years is 0.015 * 4 = 0.06 (or 6%). Here is the rule for scaling probabilities to different time intervals: if both probabilities (the original one and the new one) are no larger than 0.1 (or 10%), then simply multiply the original probability by the ratio of the new time-interval to the original time-interval, to find the new probability. This rule is an approximation which breaks down if either of the probabilities is greater than 0.1. For example

1-in-200 year events

You often read or hear references to the ‘1-in-200 year event’, or ‘200-year event’, or ‘event with a return period of 200 years’. Other popular horizons are 1-in-30 years and 1-in-10,000 years. This term applies to hazards which can occur over a range of magnitudes, like volcanic eruptions, earthquakes, tsunamis, space weather, and various hydro-meteorological hazards like floods, storms, hot or cold spells, and droughts. ‘1-in-200 years’ refers to a particular magnitude. In floods this might be represented as a contour on a map, showing an area that is inundated. If this contour is labelled as ‘1-in-200 years’ this means that the current rate of floods at least as large as this is 1/200 /yr, or 0.005 /yr. So if your house is inside the contour, there is currently a 0.005 (0.5%) chance of being flooded in the next year, and a 0.025 (2.5%) chance of being flooded in the next five years. The general definition is this: ‘1-in-200 year magnitude is x’ = ‘the current rate for eve

Coconuts and climate change

Before pursuing an MSc in Climate Change Science and Policy at the University of Bristol, I completed my undergraduate studies in Environmental Science at the University of Colombo, Sri Lanka. During my final year I carried out a research project that explored the impact of extreme weather events on coconut productivity across the three climatic zones of Sri Lanka. A few months ago, I managed to get a paper published and I thought it would be a good idea to share my findings on this platform. Climate change and crop productivity There has been a growing concern about the impact of extreme weather events on crop production across the globe, Sri Lanka being no exception. Coconut is becoming a rare commodity in the country, due to several reasons including the changing climate. The price hike in coconuts over the last few years is a good indication of how climate change is affecting coconut productivity across the country. Most coconut trees are no longer bearing fruits and thos

Cabot Institute for the Environment blog

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