Amit Mahadik was shocked when he walked out of his apartment in Sydney's Barangaroo early one morning to see 60-storey buildings fully lit up like Christmas trees.

Why are lights left on? People working late, shift workers

People working late, shift workers Cleaners

Cleaners Security guards checking the building

Security guards checking the building "Diffusion of responsibility" (it's someone else's job)

"Diffusion of responsibility" (it's someone else's job) Forgetfulness, stress, lack of motivation

Amit has worked in London and Mumbai where office automation systems, which ensure lights go off at a certain time or when there's no movement detected, are the norm.

So he asked Curious Sydney to investigate: why do office buildings in Sydney CBD keep their lights on all through the night? It's hard to believe that so many people work overnight.

There are a variety of reasons why businesses or their tenants might leave their lights on, says Esther Bailey, sustainability engagement manager with the City of Sydney.

"If you look at the city in the evening it's really important to remember the city of Sydney is driving 25 per cent of the NSW economy — flexible hours means people are genuinely in the buildings much later at night, up to 7:00pm or 8:00pm at night," Ms Bailey said.

"After they leave you have the cleaners and maintenance staff who come in to perform tasks, so lighting in the city centre up until about 10:00pm is probably legitimate work.

"After that you should see some sensors and timers kicking in in some of the modern buildings, but obviously we've got more work to do to upgrade those controls in some of our older building stock."

Executive director of the Sydney Business Chamber Patricia Forsythe says in Sydney, where the banking, finance, business services sector is such a strong part of the economy, "companies are working in the 24-hour global cycle".

"I think that people would be very surprised to discover that many, many organisations operate in the global economy and will have people working well into the night or overnight, she said.

'It's just wasteful'

If cleaners and security guards are working during the night, why aren't there systems in place to ensure lights are turned off or motion sensors activated after they leave?

The first 100 per cent LED-lit building in Sydney at 200 George St. ( Supplied: City of Sydney )

The annual Earth Hour event, which is organised by WWF and encourages people to go "lights out", has been running for more than a decade.

The biggest environmental footprint in Sydney is caused by organisations, tenants and building owners leaving lights on at night, WWF's manager of low carbon futures, Monica Richter says.

"It's burning unnecessary greenhouse pollution into the atmosphere, so not only is it bad for the environment and bad for the changing climate, it's also wasting energy when energy prices have been really high," she said.

"So if companies and tenants were better disciplined and educated about the benefits of switching their lights they'd be able to save money as well as be better environmental citizens."

The energy needed to light a big city like Sydney is enormous, according to economist Bruce Mountain from CME.

"The electricity that's used to keep the lights on needs to be produced, and most of it will be coming from coal-fired power stations in the Hunter Valley," he said.

"They're wasting energy in the first place and spewing gases into the atmosphere that we really ought not to be for no useful purpose, so it's just wasteful."

Diffusion of responsibility

Do you know where the switch is to turn the lights off at the end of the day? ( ABC News )

People are only human and perhaps one thing that's for sure is that they will often assume that someone else will act on their behalf.

A study by London's Worcester Polytechnic Institute suggested that even when they know they should, people will fail to turn off the lights because they're lacking in motivation, are stressed or they assume someone else will take responsibility.

"Do we know where the switch is? How do we know we are the last person here and the other person hasn't just gone to the loo? Do we assume the cleaners are coming in later?"

Ms Bailey says more education about what systems are available and who we expect to operate them could make things clearer for everyone.

Owners versus tenants

The MLC building has saved 38 per cent of lighting costs by installing retrofitted carparks and stairwells. ( Supplied: City of Sydney )

Those interviewed for this story agree that most building owners now recognise the need to modernise because it makes good business sense and also helps the environment.

But there's a different set of priorities for the tenants of the buildings, who may resist extra costs imposed for retrofitting new lighting systems, Ms Bailey says.

"Because despite the fact that a lighting upgrade is such a no-brainer in terms of energy savings and emissions savings and taking this unnecessary light pollution from the night sky, that's not the primary focus of the people who are in there doing business," she said.

"I think that's one of the tensions that we probably need to address as a society."

Technology advances

What can you do in your workplace? Ask building owner or company to find out how much of the electricity bill is used on lighting

Ask building owner or company to find out how much of the electricity bill is used on lighting Speak to an engineer about movement-sensitive lighting systems making sure that they have the latest lighting technology

Speak to an engineer about movement-sensitive lighting systems making sure that they have the latest lighting technology Ask manager or CEO to encourage staff to turn lights and screens off at the end of the day

Ask manager or CEO to encourage staff to turn lights and screens off at the end of the day Ask security guards to turn off any remaining lights once everyone has gone

Ask security guards to turn off any remaining lights once everyone has gone Have incentives such as green champions in the workplace to encourage sustainable energy

Have incentives such as green champions in the workplace to encourage sustainable energy Replace older lightbulbs with LED

Lighting technology has been the area of most improvement in terms of energy consumption, and buildings are now using newer systems in conjunction with architects.

It's also important for the comfort, health and productivity of workers.

"Modern lightbulbs use a tenth to a fifteenth of the amount of energy per lumen [per unit of light output] that old ones did, but we are lighting things more intensively — using topical lighting, mood lighting and fashionable lighting," Dr Mountain said.

"A lot of lighting is used for large areas, all of which need to be lit to the same intensity as individual parts of the building, so it's still a great deal of waste."

The good news

At Barangaroo, the three Lend Lease International tower buildings seen by Amit early in the morning use LED lighting, providing a 30 per cent reduction on modern lighting installations.

A double skin facade and lightwell have been used at 1 Bligh Street in the city to maximise daytime lighting. ( Supplied: City of Sydney )

"They are driven by sensors after business hours and turn off after 15 minutes of no movement being detected in a zone. Typically, floors are occupied until 9:00pm by late workers," a Lend Lease spokeswoman says.

"Most office lights are off once cleaners complete their work by about 11:00pm each night."

City of Sydney has two sustainability programs working with building owners and office-based businesses, the Better Buildings Partnership [BBP], and the City Switch Green Office program.

Under the BBP, some of the large premium building owners in the CBD have cut their emissions by 52 per cent compared to a baseline measurement in 2006.

The Federal Government's Commercial Building Disclosure program triggers environmental compliance when a space comes up for lease or for sale, which has resulted in a 30 per cent decrease in lighting intensity since 2010.

In the first 100 per cent LED-lit building in Sydney, 200 George St, light bulbs only need changing every 12 years, reducing energy consumption by 30 to 50 per cent.

At the iconic but older MLC Centre, retrofitted carparks and stairwells have saved 38 per cent of lighting costs, and a double skin facade and lightwell have been used at 1 Bligh Street in the city to maximise daytime lighting.

WWF's Ms Richter believes there's been a definite shift in attitude, with property owners committing to becoming carbon positive by 2030 by investing in renewable energy or reducing their footprint.

"It's up to all of us — whether you're in Parramatta or Hornsby or the city CBD or north Sydney, it's being able to get tenants and educate them that they need to switch off the lights at the end of the day," she said.

Who asked the question? Amit Mahadik's question won the audience vote for investigation by Curious Sydney. Amit is passionate about sustainability and concerned people take unlimited consumption for granted. His previous employer, JP Morgan, installed automated systems for lighting its offices because of a keen focus on energy conservation. Amit finds it hard to believe that every floor in a 60-storey building needs to be lit all night. "Is it really people working all through the night in these offices or is it somebody who kept the lights on and just forgot to flick off the switch?"

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