Why do New York buildings stay lit all night?

While ecology and energy savings are increasingly discussed, many office buildings in New York remain lit throughout the night. Here's why.

New York’s Nighttime Energy Consumption

Walk through New York at night or look at photos of the skyline after dark, and you’ll notice something striking: entire floors of office buildings stay lit throughout the night, even when few or no employees are inside. This is especially visible in the Financial District, where the One World Trade Center glows brightly.
All those illuminated offices seem like an enormous waste of electricity. Con Edison, New York’s main power utility, has actually done the math: the city loses an estimated 5,200 megawatts of electricity every hour during the night.

There’s actually a practical reason behind this energy use. Buildings stay lit primarily for aircraft visibility. Air traffic continues around the clock at New York-JFK, Newark, and LaGuardia airports, carrying both passengers and cargo. While flight paths are well-defined, maximum visibility helps pilots navigate safely.
The same applies to helicopter flights in New York. Manhattan has 3 heliports, 2 of which are open to the public, and pilots need clear sight lines to judge distances from surrounding buildings. Building lights are ultimately a safety measure.

The question of nighttime office building lighting remains controversial in New York. With modern instrument flying and GPS technology, some argue that the red lights on top of buildings are sufficient, making full illumination unnecessary.
In 2015, a city council member introduced a bill requiring office buildings to turn off unoccupied open-plan offices and individual offices at night to save energy. Animal advocates joined the debate, pointing out that building lights disorient birds and cause fatal collisions. Opposition has been strong, however.
New York is moving slowly on this issue, and buildings are likely to stay lit for the foreseeable future.