The energy reality behind Cape Town's water crisis – and why the U.S. should care

Kate Zerrenner

In Cape Town, South Africa, the countdown is on for Day Zero when water taps in the city of 4 million people are expected to run dry.

Yet, while this water crisis has been making headlines worldwide, nobody’s talking about the connection between water and energy. In a rapidly changing climate, we should.

Cape Town may be the first major city staring down a water scarcity crisis, but it’s not alone. One-quarter of the world’s large cities, including at least two in the United States, are “water-stressed,” a 2014 study found.

As it turns out, many of them also happen to rely on the world’s thirstiest energy source: coal.

23,000 gallons of water a month to power a single home 

In the symbiotic relationship known as the energy-water nexus, we use power to treat and distribute water, while water is used to process and deliver power. This is why our energy choices directly affect our water resources – and lack thereof.

Traditional power resources such as coal, natural gas and nuclear fission require on average 25 gallons of water to produce one kilowatt-hour of electricity. Coal plants top the list; they withdraw between 20 and 60 gallons of water per kilowatt-hour, depending on the plant’s cooling technology.

A typical American home uses about 900 kWh per month, which translates into nearly 23,000 gallons of water per household per month – just for electricity.

Which brings us back to Cape Town: 92 percent of South Africa’s power comes from coal. So while residents may be taking shorter showers and doing their best to conserve water, the country’s power plants are gulping it down.

Is Miami next?

Cape Town is in uncharted water territory and with climate change rapidly altering temperatures and weather patterns, U.S. cities probably aren’t far behind.

Climate predictions show an increasingly hot and dry America and the evidence is all too visible.

Only six months after Hurricane Harvey, Texas is back in drought. California could be living through more than a decade of drought, which has already upended the state’s agricultural industry.

And the water stress is spreading eastward. New England and the Southeast recently suffered unprecedented droughts – and Miami is now expected to be the first U.S. city to run dry.

This trend tells us that now’s the time to have a closer look at the energy-water nexus, and how to make the best use of what water we’ve got left.

These power sources use almost no water

The upside of all this is that we have a powerful water conservation tool with multiple co-benefits at our disposal: clean energy. Solar photovoltaics and wind power use virtually no water. Energy efficiency uses none.

To this day, 85 percent of U.S. electricity comes from our thirstiest energy resources, fossil fuel and nuclear power plants. Expanding the use of renewable energy and energy efficiency, while weaning ourselves off the thirstiest power sources, will lead to huge water savings at the right time.

This is our opportunity here and around the world as we plan for the reliability and resilience of our energy and water systems. It’s no longer possible to ignore the impact our energy sources has on critical water supplies, and vice versa.

We have already begun to turn toward a cleaner energy economy. The question now is whether we can ramp things up before the next big city goes dry.


You are not accounting for the water consumed by manufacturing solar panels and windmills, though, are you? Manufacturing these tools consumes tremendous amounts of power.

Please also talk about the importance of “passive” energy design. Most of our energy use is related to heating, cooling or constructing the structures we live and work in. Design/construction strategies that use daylight, window orientation, and natural convection to light, heat and cool our buildings use no energy or water. Renovating existing buildings and re-using existing construction materials saves the water which would be consumed by manufacturing new construction materials. Wood construction sequesters carbon for the life of the structure, and engineering and building code innovations now make it possible to build very durable structures up to 13 stories high primarily out of wood (mass timber, laminated wood beams/columns).

There are many ways to save water!

February 28, 2018 at 5:35 pm

Does the one-time cost of building the panel or windmill really matter though, considering the lifetime it will have before it needs to be replaced? If you did a calculation to determine how many kilowatt hours you get per liter of water expended, I am guessing the numbers for a panel or windmill would be far far far more favorable than a coal plant, where the water is needed to produce the energy directly.

Robert Burnett
March 4, 2018 at 2:46 pm

In reply to by Kristine

Some of your points may be quite valid, but you neglect to mention just how much water goes into not only mining the coal, but throughout the ENTIRE process — from extraction, cleaning, storing, transport, etc. to burning it for energy. Coal uses huge amounts of water.

March 5, 2018 at 7:05 am

In reply to by Kristine

One way we could save quite a bit of water would be to give up on fracking for oil & gas, as each well fracked requires between 12 and 15 acre-feet of water, and then huge amounts of permanently-contaminated fracking wastewater is injected into our saline aquifers deep underground, permanently-contaminating them too.

Moreover, generating electric power using natural gas involves the use of quite a bit of cooling water too, as well as the release of lots of CO2 from burning natural gas, as well as the release of lots of methane both from leaking oil & gas wells as well as from enroute distribution system leaks. The fact is that methane traps 256 times as much heat as CO2 does over the first two months after its emission, slowly declining to 115 times as much heat as CO2 at 5 years after methane emission, to 86 times as much heat at 20 years following methane emission. Natural gas is almost entirely methane in-fact.

Now salt water isn't usable for much but if we run substantially short on water those saline aquifers below us could come in handy for desalinization if they weren't so polluted by fracking wastewater injection.

Even our fresh aquifers get polluted on-occasion when well cementing fails underground and frscking fluid leaks into aquifers. Would you believe that several peer-reviewed studies have found that 5-6% of all fracking wells suffer immediate cementing failure underground during high-pressure fracking, (Davies et al, Marine and Petroleum Geology), or that up to half of oil & gas wells suffer cementing failure underground at 40-50 years in age (Kang, et al, Stanford University, Princeton University, multiple studies)?

Sounds like the way to save the most water and keep temperature from rising too much would be to keep as much oil, coal, uranium, and natural gas in the ground as possible.

You know what else happens if temperature rises too much? Rising sea-level will not only render a whole lot of near-shore real estate worthless but will also infiltrate and pollute coastal aquifers with salt water too.

Mark Richardson
March 9, 2018 at 8:27 pm

In reply to by Kristine

24/7 cheap green energy is coming. See
Atmospheric water will soon be extremely inexpensive and can be obtained even in areas of 5% humidity due to breakthrough technology. Difficult to believe new science will change the energy and water landscapes.

Mark Goldes
February 28, 2018 at 9:19 pm

This article is skewed. Manufacturing and mining of rare earth elements used for solar and wind farm components is very energy intensive and environmentally deleterious.

David Freudenrich
February 28, 2018 at 11:29 pm

Consider please the relatively small amount of rare earth materials to make a solar panel one time that will generate electricity for decades in comparison to coal that has to be mined and burned continuously to generate electricity.

Bob Feldman
March 4, 2018 at 12:25 pm

In reply to by David Freudenrich

Certainly not compared to the fossil fuel alternatives. We should also absolutely be recycling, and also minding our spent batteries.

phil brooke
March 4, 2018 at 10:48 pm

In reply to by David Freudenrich

The shale oil process in Canada also consumes tremendous amounts of water. Of course, it is “out of sight, out of mind,” so who cares?

Tim Helble
March 5, 2018 at 11:37 am

In reply to by David Freudenrich

Rare earths are not needed for the semiconductors that are solar panels.

The water cost of clean energy systems will decrease with time: an all-solar power grid requires zero water. Materials can be recycled when solar panels degrade after 15-20 years of use. (The same goes for “rare” earths used in powerful permanent magnets.)

Jeff LaCoss
March 8, 2018 at 9:43 pm

In reply to by David Freudenrich

Ultraconductors are equivalent to room-temperature superconductors. Motors and generators employing ambient temperature superconductors will need no permanent magnets or rare earth elements and can dispense with all or most of the iron used in conventional versions. See Ultraconductors at

Mark Goldes
March 2, 2018 at 10:42 am

Here educate yourself about mining rare earth minerals:

March 5, 2018 at 10:42 am

Here. Educate yourselves. Solar does use an appreciable amount of water.…

March 5, 2018 at 11:01 am

Odd to consider water used for power plant cooling as “consumed”, it’s not gone the way water flushed in a toilet or used to irrigate a crop field, right? Surely it cycles, at least in part, and once used for cooling it can be made available for other uses.

E. olson
March 7, 2018 at 3:10 pm

That is correct, E. Olson, which is why this blog post specifically says that the plants “require” water, as opposed to “consume” water. However, much of this water can never be recycled — or it may take time before it’s pumped back. That’s why these plants can have such an impact on the water table.

Karin Rives
March 8, 2018 at 9:57 am

In reply to by E. olson

It is potentially confusing to include power plant cooling water, that is as you say merely “required”, in an article about the cause of a city actually running out of water, that situation is clearly a matter of consumption. Without providing more detail I think most readers will conclude power plants “use up” the water, 25 gallons per kWh, as the other uses you refer to use up the water (you mention showers). Showers and toilets introduce fecal matter so gray and black waters must be treated, but cooling water should be reusable more readily.

I hate coal, I just think distinctions should be made. An article on reuse of water from different sources would be good to see, and specifically a look at the use and misuse of water by the power plants in the vicinity of Cape Town would inform the readers more about the details on the ground there.

The point could be made that since water for cooling requires no costly treatment (unless accidentally contaminated in the process?) it is really absurd that it’s not captured promptly in some way, in a setting facing the prospect of zero water soon. Seems like cooling water should be the highest priority given its unique status as “used” but unimpaired.

March 8, 2018 at 11:04 am

In reply to by krives

“However, much of this water can never be recycled — or it may take time before it’s pumped back.”

Would be useful to know the percent losses both in Cape Town power plants and in the world’s most efficient plants, using best practices.

(Don’t infer from these questions that I like coal. We could and should be moving off all fossil fuels ASAP!)

March 8, 2018 at 11:09 am

In reply to by krives

We should also keep in mind that research is in progress to simplify energy collection. Flexible collecting panels and paints. There are already conducting inks. The real issue to also be addressed is power losses by transporting electrical energy from a “power generating farm” to individual consumers. There are enourmous losses involved.

Hopefully in the future, each consuming entity will generate its own needs. This would make electric cars a replacement rather than an alternative with limitations. Moreover, present-day power grids are an attractive target for terrorist attacks and present national security risks.

S. Dan Dimitrijevich
March 7, 2018 at 6:01 pm

Why is there never any reference to the viability of desalination in this wealthy nation? Yet they spend billions on their military! Are they more paranoid about their relatively poor neighbors’ potential invasion…more so than the immediate welfare of their own citizens?! Pathetic.

Mike Scharrer
March 7, 2018 at 6:10 pm

Steam cycle electricity production requires a heat source and a cooling mechanism. The temperature differential obtained between these two temperatures are proportional to the efficiency at which the plants operate… Often, evaporative cooling is used and results in the evaporation of the cooling water, which goes into the atmosphere and later falls as rain… This discussion only considers the consumption of water for cooling without considering the resulting rain fall….

David Sims
March 8, 2018 at 9:14 pm

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