The green case against digital billboards

By Fred Kuhlman • januari 21st, 2011

This is reprint from, written by Barnaby Page.

While digital outdoor’s many critics in the U.S. have largely focused on traffic safety and light pollution, a Pennsylvania architect and urban planner has opened a new front, charging that digital sites consume vastly more energy than conventional billboards.

A paper from Gregory Young, available from the Scenic America pressure group and produced in collaboration with Philadelphia’s Society Created to Reduce Urban Blight (SCRUB), says that static billboards annually consume less energy than an average U.S. home – about 7000kWh for an advertising site and 11,000kWh for a household – but digital outdoor signs can require more than 40 times as much as their non-digital counterparts.

Among the worst performers are billboards from Eraled, ThinkSign and Optec, the report says, with one Optec unit eating 324,000kWh a year. The best performers include Barco and Lighthouse, with power consumption assessed by Young at 74,000kWh and 93,000kWh respectively.

“Out-of-home advertising is simply not an appropriate or responsible application for digital technology,” the report says. It dismisses the contention that digital billboards should gain green kudos because LEDs are more energy-efficient than the conventional light sources used to illuminate static billboards.

“These claims overlook one key bit of common sense: whereas traditional, static signage is illuminated by two or three ‘inefficient’ lamps at night time, digital signs are comprised of hundreds, if not thousands, of ‘green’ LED bulbs, each using 2-10W, lit 24 hours a day. For instance, a 14-by-48-foot LED billboard can have between 900 and 10,000 diodes,” the report says.

“Bulb-to-bulb comparisons are irrelevant in this context,” it concludes.

To exacerbate matters, says Young, digital billboards are frequently operated at higher brightness levels than necessary. He notes that when digital-signage technology supplier Noventri experimented with running displays at half-brightness, it reduced power consumption by nearly 40 percent without sacrificing readability.

But it is not only lighting that attracts Young’s scepticism. He notes that digital billboards also draw power for their cooling systems, especially during periods of hot weather, when they add to the already onerous load on the power grid imposed by buildings’ air conditioning.

He quotes a suggestion that digital billboards will need to be replaced roughly every 11 years, as opposed to 15 years for static billboards, and says that when defunct they generate more waste, although he acknowledges that digital units “lack the potentially toxic adhesives” used in static signs.

What’s to be done?

Timing his report to coincide with a major revamp of Philadelphia’s zoning rules, Young does not propose an all-out ban similar to those that have been enacted in cities such as Denver and Dallas, but calls for tight restrictions on light levels and hours of operation.

He begins by advising that the zoning rules should “include any and all digital signage, defined as any sign capable of displaying words, symbols, figures or images that can be electronically or mechanically changed by remote or automatic means, not just those that are animated, flashing, or intermittent, which can be subjective descriptions”.

Among his prescriptions for acceptable operation are that “the illumination projected from any [sign] shall at no time exceed 0.1 foot-candle onto a residential [site], and 1.0 foot-candle onto a non-residential [site]. This should apply to light emitted from any form of signage, on-premise or off-premise. We also propose specific luminance limits of 100 nits for night-time conditions, applicable to all digital signage.”

Further, suggests Young, “off-premises digital signs [should] be extinguished automatically no later than 11pm each evening until dawn. Signs for establishments that operate or remain open past 11pm [should] remain on no later than one half hour past the close of the establishment.”

Draconian requirements, perhaps, but what’s unusual about Young’s contribution to the debate over digital billboards is that he scarcely mentions the generalised concept of visual blight; deals in quantifiables; and proposes restrictions that seem achievable, albeit undesirable for media owners, rather than refusing to settle for anything short of an outright prohibition. The shape of Philadelphia’s rewritten zoning code will show whether that approach is persuasive to the planners.

Oh no they don’t

Meanwhile, one digital-billboard vendor was quick to respond to the publicity received by Young’s report. Yesco Electronics says its units require just a quarter of the power they used six years ago, and that consumption is continuing to drop.

Yesco even says that at night its billboards use less power than “most traditionally-illuminated billboards”.

“We have seen a steady decrease in power requirements year over year, and expect the trend to continue,” said VP and general manager Rod Wardle. “In 2011, we anticipate another year-over-year decrease of 25 percent in power consumption.

“Rapid improvements in efficiency make yesterday’s power-consumption data out-of-date,” he added in an apparent reference to Young’s paper.


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