Why have people in Tokyo been told to ration electricity and could it happen in Scotland?

As temperatures climbed to record levels around Japanese capital Tokyo this week, authorities issued an urgent call to 37 million people in the region – turn off the lights or face an electricity blackout.

The Japanese government said its electricity reserves were set to dip on Monday afternoon and asked citizens to turn off “unnecessary” lighting between 3pm and 6pm – but to keep air conditioning units running in a bid to avoid heatstroke. It said a similar warning was likely to be issued on Tuesday.

The move comes as temperatures in Tokyo itself hovered around the mid-30s, while in Isesaki, north-west of the capital, thermometers climbed to a record 40.2C – the highest ever recorded in Japan in June.

In Kawagoe city, around 12 miles from Tokyo, a 94-year-old man died of suspected heatstroke after he was found in a non-air conditioned room, while more than 250 people in the capital were treated in hospital for suspected heatstroke.

Pedestrians walk on a street in Tokyo's Ginza district. Picture: AFP via Getty Images

In Scotland, electricity shortages caused by high temperatures are not likely to be a problem in the foreseeable future – only 0.5 per cent of homes in the UK have air conditioning, according to a 2008 report by Mintel.

However, the UK Government has warned people living in the UK could face electricity rationing in winter, when the demand for utilities reaches its own peak amid freezing weather conditions.

Last month, Prime Minister Boris Johnson admitted the UK Government had drawn up contingency plans for electricity rationing.

Under the proposals, six million homes could see their electricity use curbed, primarily during morning and evening peaks, in restrictions that may last more than a month.

The reasons behind potential power shortages in the UK are different – however, the impact could be similar, with households potentially facing blackouts as supply and demand converge amid spiralling global utility costs.

Mr Johnson has insisted the Government “does not expect” to have to use rationing. But various scenarios have been modelled, depending on whether Russia limits gas supplies to the European Union amid the Ukraine conflict, which would push demand higher globally.

The UK is not largely reliant on Russian gas supplies, unlike other countries such as Germany. The Government has, however, requested that coal fired power stations in England delay their planned closures.

Worse modelling was reported for a scenario in which Russia cuts off all supplies to the EU.

The UK suffered blackouts in the 1970s when a series of strikes by coal workers over wages saw electricity supply restricted. The country moved to a three-day working week to limit energy usage, while people were told to heat only one room and, like in Japan this week, turn off non-essential lighting.

TV channels were forced to stop broadcasting by 10:30pm, while even the Government held some meetings by candlelight.

Energy experts have warned in recent months that many people have already implemented self-imposed energy restrictions, cutting back on their use of heating, or stopping using the oven, amid soaring utility bills.

A poll published earlier this year by Advice Direct Scotland found 65 per cent of people were already rationing energy use at home.

A spokesperson for Energy Action Scotland said: “The way we use energy is changing and demands are obviously increasing. Our priority remains, as always, vulnerable consumers and we are working with energy companies to ensure that everyone is protected as new models are explored.

“More immediately we are concerned by the spiralling number of households in fuel poverty, many of whom are being forced to ration their energy use because they can no longer afford to meet the basic needs of heat, light, cooking and hot water. The next price cap rise will see more than 800,000 households in Scotland ration energy use because they live in fuel poverty and this has to be our first priority.”

In Japan, the government said that excess generating capacity for electricity was expected to drop to 3.7 per cent on Monday afternoon in Tokyo and eight surrounding prefectures. The Government has said it believes a buffer of 3 per cent is necessary for stable power supply.

The heatwave comes with weather officials having announced the earliest end to the annual summer rainy season since the Japan Meteorological Agency began keeping records in 1951.

A statement from the country’s Ministry of Economy, Trade and Industry (METI) said: “Today, June 27, the power supply and demand in the Tokyo Electric Power Company's jurisdiction is expected to become severe, so a warning of tight power supply and demand is being issued.

"But the reserve rate is expected to fall below 5 per cent per cent mainly in the evening hours tomorrow. Therefore, we will continue to issue warnings about the tight supply and demand of electricity.

“During hot hours, use air-conditioning, etc appropriately to rehydrate, and be careful not to suffer from heat stroke, and turn off unused lights to save electricity within a reasonable range.”

METI director of electricity supply policy Kaname Ogawa added: “We are struck by unusual heat for the season. Please co-operate and save as much power as possible.”

Many countries across the world, particularly in Africa and countries in south and central America, suffer regular power outages, for a variety of reasons.

Rolling blackouts are common in South Africa, which has suffered power shortages for the past 15 years, but has seen regular blackouts ramp up in the past year amid problems with generation units.

Power cuts are most common in Pakistan, but other countries like Iran have daily summer mass blackout programmes every year.