Water and energy

Water and energy as well as carbon dioxide – CO2 – are intricately linked. You need water in order to generate energy. You need energy in order to make water safe for human consumption, and transport it to and from our sinks, toilets and showers. The links between water and energy are sometimes referred to as the Water-Energy Nexus.

So remember: if you reduce your water use, you will save energy and lower your CO2 output. If you use less energy, you will save water and reduce CO2.

Hydro electricity dam

Water for energy

Energy production uses water for extracting fuels from the ground, processing and transporting them. The link between water and energy is most obvious with hydroelectric power, which requires a steady water supply.

Water is also necessary to generate thermoelectric power. In 2000, the production of thermoelectricity accounted for 39 per cent of all freshwater withdrawals in the United States, roughly the same amount of water as that withdrawn for agriculture 1. About 95 litres (25 gallons) of water are withdrawn for every kilowatt-hour (kWh) of thermoelectricity generated 2.

The picture for water and energy use is similar in other countries. In Germany, 82 per cent of extracted freshwater is used by industry. Of this, 72 per cent goes to utility companies for cooling power plants  3.

Water for energy: Two cooling towers

Energy for water

The links between water and energy are many.

Public water supply and treatment facilities in the United States use 56 billion kWh of energy per year to transport and treat drinking water and wastewater  4.

Another study found that 12.6 per cent of all energy used in the United States in 2010 was directly linked to water use 5. In California, where water has to be pumped over long distances, nearly 20 per cent of total electricity consumption is water-related 6. Transporting, treating, heating, cooling and pressurising water uses 25 per cent more energy in total than it takes to light every household and business in the US 7. Households in Germany use twelve times more energy for hot water than for lighting 8. Letting your tap run for five minutes uses as much energy as a 60-watt light bulb in 22 hours 9.

Water and energy are linked throughout the drinking water cycle:

  • Transport: Energy is needed to move water between places at every stage of the cycle.
  • Extraction: Surface water is drawn from lakes and rivers; groundwater is pumped from aquifers and transferred into storage.
  • Treatment: Energy is required to process water to make it safe for drinking.
  • Use: End users consume energy mainly to heat or cool water.
  • Wastewater: Energy is used  to pump wastewater to the treatment plant and to clean it there.

Taking CO2 into account when looking at water and energy, Waterwise estimates that about 5.5 per cent of UK greenhouse gas emissions can be attributed to heating water in homes. The water industry accounts for another 1.0 per cent of emissions 10.

Hot water and energy generate CO2 in households

When you look at water and energy use coupled with CO2, some interesting facts emerge:

  • CO2 emissions from heating water in homes are mainly related to the volume of hot water used, and you can reduce those emissions by using less.
  • If 1 per cent of homes in the United States installed water-efficient fixtures, 100 million kWh of electricity could be saved each year. This in turn would cut CO2 emissions by 80,000 tons, which is equivalent to taking nearly 15,000 cars off the road for a year 11
  • If every home in the UK used 5 per cent less hot water, the CO2 savings would be the same as taking almost 600,000 cars off the road 12

Hot bath water use in the bathroom

Save water and energy, cut your bills

In Germany, heating water accounts for 10 to 45 per cent of all domestic heating costs 13. The figure is around 30 per cent in the UK  14 and 13 per cent in the US 15.

Since water and energy use is responsible for a considerable part of people’s utility costs, saving water and energy is good for the environment and good for you.


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