|Fig. 1: Radiohead's elegant LED stage lighting. (Source: Wikimedia Commons)|
I have always appreciated rock concerts for entirely the wrong reasons. As an engineer, I marvel at the cascade of currents and magnetic fields flowing through the PA stacks, producing a typhoon of acoustic waves that ricochet about the venue. My brain gawks at the complexity of the signal processing as dozens of instrumental inputs are filtered, equalized, delayed, and amplified. And yes, there are some musicians, too.
The power involved in one of these productions has always intimidated me. When the UK pop-turned-avant-garde rock ensemble Radiohead hired a consulting group to reduce the "carbon footprint" of their 2008 tour, I became curious: how much power does a rock concert actually use?  And, maybe more importantly, do we need to scale back the gratuitous production values that make chest-pounding, seizure-inducing concerts the epic experiences that they are in the name of a secure energy future?
Every concert is, by design, a unique experience. Venues range from hip, underground clubs supporting a few hundred fans, to major arenas designed for occupancies upwards of 100,000. For this investigation, it seemed a propos to use the 2008 Radiohead tour as a case study. A production on the scale of a Radiohead tour involves an incredible number of people, vehicles, materials, and other energy-consuming things. Three key elements of a concert which we have some insight into are the sound amplification, lighting fixtures, and audience transportation.
The US portion of the Radiohead tour used 12 racks of 3 L-Acoustics LA8 audio amplifiers, as well as 6 custom front-fill speakers powered by Crown IT 6000 amplifiers. Assuming each front-fill was two-way, requiring two channels of amplification, this would require 6 crown amps.  Both varieties of amplifier are specified to draw 11 A at 120 V for typical operation, resulting in an approximate power draw of 1500 W per amp. [3,4] Supposing a generous performance (lots of encores, etc) lasting 2 hours, the total energy consumed by sound amplification would be
Towards their goal of a "carbon neutral" tour, Radiohead insisted on using exclusively LED-based light fixtures on and back stage (most performances rely heavily on dimmable, incandescent PAR-64 1 kW theatre lighting). How much power did Radiohead's innovative LED system draw? Table 1 indicates the number of each LED fixture and corresponding maximum electrical power consumption. [5-11]
|Table 1: Power Consumption by Fixture Type.|
Again assuming a two-hour concert, the energy consumed would be
As an intriguing comparison, consider the power used by the 150 PAR-64's in Ronnie James Dio's Heaven and Hell tour: 
This analysis is too simplistic to conclude that Radiohead's LED lighting was more efficient by a factor of 5. Stage lighting is dynamic - hardly ever would all fixtures be on at full capacity simultaneously. The key point, however, is that between two fairly different approaches to concert lighting, the maximum energy consumed by fixtures is roughly 1 GJ.
A less obvious energy component of a rock concert is the gasoline burned in getting the audience to and from the show. How much gasoline is used? Consider Radiohead's performance at the Hollywood Bowl in Los Angeles, with a seating capacity of 18,000.  We'll assume that everyone in LA drives at a generous three passengers per car, and that spectators are travelling an hour on average (at highway speeds, 60 miles) each way to attend the show. This average distance is totally made up, based on a sense of what I would be willing to endure - it will turn out that this distance may vary greatly without changing the final conclusion. With these assumptions, the amount of gasoline used is
Or, in terms of joules, 
It's worth noting that the Hollywood Bowl was a relatively small venue on the tour. The band performed at many larger, outdoor festivals, such as Chicago's Lollapalooza with a turnout of 75,000 fans each day. 
It is clear from this cartoonishly simple calculation that the amount of energy used by the electrical elements of the band's performance is pitiful in contrast to that used by the audience in attending the event. Subtle changes in the choice of lighting design, PA arrangement, etc, will not account for a discrepancy this large. This conclusion is the same even if the average distance traveled per car were reduced by a factor of 10. Reducing the energy impact of a rock concert is synonymous with reducing the impact of transit in general. As such, any energy-conscious artist should not limit themselves in the scope of their production, but rather should consider where they perform and how the audience will get there. The conclusion of the 2007 carbon emissions analysis was essentially the same, claiming that the total band contribution including air travel, catering, rehearsals, etc. was dramatically less than that due to fan travel. 
As for my second question, should we be concerned about spending a few terajoules to see our favorite band? The five counties of the Los Angeles metro area use this amount of electrical energy in about 6 minutes (calculated using data from the California Energy Commission. Sadly, finding an official document with this number is nigh impossible). Radiohead's effort to control their energy consumption is admirable, but the order on which they directly contribute is too small to be significant. Nonetheless, by raising awareness with their fans, they may be able to affect change on a global scale.
© Patrick Landreman. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 C. Stentiford, "Ecological Footprint and Carbon Audit of Radiohead North American Tours, 2003 and 2006," Best Foot Forward, Ltd., July 2007.
 D. Emerick, "Tour Profile: Radiohead," Mix Magazine, 1 Oct 08.
 "LA8 Amplified Controller, L-Acoustics, LA8_UM_EN4-0, April 2011. [Copied and re-posted by permission of L-Acoustics.]
 I-Tech Series Operations Manual, Crown Audio, Inc., 137289-10, November 2007.
 J. Moody and P. Dexter, Concert Lighting: Techniques, Art, and Business, 3rd Ed. (Focal Press, 2009).
 "BB4 User's Manual," i-Pix, January 2009.
 "Satellite Mk II User's Manual," i-Pix, December 2011.
 "ColorReach TR Powercore Product Guide," Philips Color Kinetics, DAS-000048-00 R00 09-09, September 2009.
 "iW Blast TR Product Guide," Philips Color Kinetics, DAS-000012-00 R03 05-12, May 2012.
 "Versa TUBE Technical Manual," Element Labs, January 2007.
 M. Buckland and J. Henken, The Hollywood Bowl: Tales of Summer Nights (Princeton Architectural Press, 1999).
 S. Hibbs, "Two Hydrogen Cars," PH240, Report #1 (2010)
 G. Kot, "How Lollapalooza Changed Chicago's Concert Landscape," Chicago Tribune, 27 Jul 08.