What will happen if everyone on Earth turns on the lights at the same time, — Smithsonian researcher

An American researcher from Smithsonian Institution Harold Wallace asked an interesting question about what would happen if all the people on the planet turned on the lights at the same time. 

Obviously, this will lead to an immediate increase in electricity demand and create balancing problems for power plants. Power plants generate electricity from coal, natural gas, uranium, and water, wind and sunlight.

The generated electricity is supplied to the power grid for further transmission and distribution to consumers. To maintain the stable operation of the grid, electricity must be supplied on demand. When someone turns on a light, they consume electricity from the grid. The generator must immediately deliver the same amount of power to the grid. If the balance of the system is disturbed even for a few seconds, a blackout can occur. 

System operators use sensors and sophisticated computers to track electricity demand so, that they can adjust production according to need. The total demand for electricity, called load, varies greatly from hour to hour and from season to season.

If everyone on the planet turned on the lights at the same time, power plants would have to rapidly increase production to prevent a systemic failure. Coal and nuclear power plants can generate a lot of electricity at almost any time, but in the event of a maintenance outage or breakdown, they can take a long time to recover. In addition, they are slow to respond to changes in load.

Natural gas-fired power plants are more responsive to changes in load, so they are used more often during periods of high demand, such as hot summer days. Renewable energy sources, in particular, wind and solar power plants, are less polluting, but the balance of generation is more difficult to control, as solar activity and wind speed are highly variable.

Energy companies use powerful batteries to compensate for the imbalance of electricity during the growth/decline in demand. However, the capacity of batteries still does not allow storing enough energy to supply, for example, an entire city. Some hydropower operators can pump water into lakes during periods of low demand and then release this water to generate electricity when demand is high, by passing it through turbines. 

If everyone on the planet turned on the lights at the same time, two factors would prevent the destabilization of the power grid. First, there is no single integrated power system. Secondly, over the past 20 years, LED light bulbs have replaced many older electric lights. LEDs work differently than earlier bulbs and produce much more light from each unit of electricity, so they need much less power from the grid.

According to the U.S. Department of Energy, using LED bulbs saves the average household about $225 per year. As of 2020, nearly half of all homes in the United States used LEDs for most or all of their lighting needs.

In addition, turning on all the lights on the planet at the same time would lead to large-scale light pollution. The light reflects off the haze and dust particles in the air, creating a diffuse glow that darkens the night sky. Even well-designed lighting systems can make the problem worse, making cities and highways visible from space and the stars — invisible to us.

Such light pollution can disrupt people’s natural sleep-wake cycles, disorient insects, birds, sea turtles, and other wildlife. The sky would be much brighter, and there would be no stars at all.