Collecting kinetic energy from roads; REPS turns traffic into a power plant

REPS announced a $23.6M equity financing round to scale its Road Energy Production System, a patented “road power plant” that converts vehicle traffic into electrical energy. For years, Green Prophet has followed the strange, persistent dream of harvesting energy from roads. Back in the early 2010s, Israel experimented with piezoelectric roads in Tel Aviv, when […]

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As heat waves intensify from Dubai to Dallas, millions of air conditioners quietly drip gallons of clean water into drains every single day. This is pure water going down the drain, even though there are many uses for AC water as we’ve discussed over the years.

Now researchers in Jordan say that water — called AC condensate — may be one of the most overlooked alternative water sources in cities worldwide. The 2024 study, published in Case Studies in Chemical and Environmental Engineering, tested water collected from 120 air conditioning units and found the condensate had surprisingly high quality, with low dissolved solids, low heavy metals, and chemistry close to distilled water.

That means the water dripping from your air conditioner may already be usable for gardening, cleaning, flushing toilets, topping up humidifiers, or cooling systems — instead of disappearing into the sewer.

And in hot climates, the numbers add up fast.

How Much Water Does an Air Conditioner Produce?

According to their study, which we will sum up here, modern AC systems can generate between 15 and 70 liters of water per day (about 15 gallons) depending on humidity and unit size. A single apartment AC unit stuck in a window in Brooklyn running through a humid summer can easily fill buckets overnight.

Office towers, malls, schools, hospitals, and hotels produce dramatically more. In tropical cities like Singapore, Miami, Tel Aviv, Mumbai, or Bangkok, entire buildings are beginning to recover AC condensate as part of water-saving systems. These feed into flower beds, toilets and irrigation systems.

What was once considered waste is becoming infrastructure.

What Is AC Condensate Water?

Air conditioners do more than cool air. They also remove humidity. When warm moist air hits the cold evaporator coils inside an AC unit, the moisture condenses into liquid water, which is similar to droplets forming on a cold glass. That water is called condensate and most systems simply drain it away.

But researchers from Jordan say that should change so looked to see if it was safe to use.

Is AC Water Safe?

The Jordanian researchers tested for:

pH
dissolved solids
turbidity
nitrates
hardness
chlorine
heavy metals including lead, cadmium, arsenic, chromium, copper, nickel, zinc, iron, and aluminum

Most values, they found, were far below drinking water and irrigation safety limits which means that when in a pinch it may be okay to consume. Except, they warn that AC condensate water is not automatically safe to drink directly from the pipe.

The water can pick up:

bacteria
fungi
mold
dirt from evaporator coils
contaminants from poorly maintained systems

The study itself notes that microbial testing was limited and recommends further biological analysis before treating AC condensate as potable water. So while AC water often behaves chemically like distilled water, most experts recommend using it first for non-drinking purposes unless it is filtered, sterilized, or professionally treated.

Best AC Water Uses at Home

Air Conditioner Water for Plants

AC condensate is low in salts and minerals, which many plants prefer.

Good for:

balcony gardens
houseplants
lawns
urban farming
drip irrigation

Some gardeners even prefer condensate over hard tap water.

Cleaning Floors and Windows

Because it contains very low mineral content, condensate water often leaves fewer streaks or residue marks.

Flushing Toilets

One of the easiest large-scale reuse applications. Toilets account for a major percentage of household water use.

Steam Irons and Humidifiers

Since condensate is low in minerals, it can reduce scaling inside appliances.

Car Washing

Especially useful during drought restrictions.

Cooling Towers and Industrial HVAC Water Recycling

Commercial buildings increasingly recycle condensate internally to reduce freshwater demand.

Why Cities Are Suddenly Interested in HVAC Water Recycling

Climate change is increasing both:

water shortages
air conditioner use

That means hotter cities paradoxically create more condensate water precisely when freshwater becomes scarcer. The researchers point to Jordan as an example of extreme water stress, but the same logic now applies to California experiencing droughts periodically, southern Europe, India, the Gulf states, Australia, and parts of Latin America.

Entire urban districts may eventually capture AC condensate the same way cities harvest rainwater today.

The Biggest Problem? Buildings Aren’t Designed to Reuse AC Water

Ironically, the study found that one of the main barriers is simple plumbing. Most AC drain lines connect directly into sewage systems which means the water disappears before anyone can reuse it.

Newer green buildings are beginning to change this with:

dedicated condensate recovery systems
rooftop storage tanks
graywater integration
irrigation hookups
smart filtration systems

In humid megacities, future building codes may eventually require condensate capture.

AC Water Reuse Isn’t Just for Dry Countries

The study focuses on Jordan because of water scarcity, but the implications are global.

In wealthy cities, AC condensate water can:

lower water bills
reduce urban water demand
support green roofs
cool public spaces
irrigate landscaping
increase drought resilience

Data centers, luxury hotels, airports, hospitals, and universities are already experimenting with condensate recovery systems. In a warming world, every building becomes a tiny atmospheric water harvesting machine. And most people still let it run down the drain.

If you are inspired by this article on AC water, learn here how a company from Austria is turning streets into tiny power plants by harvesting energy from trucks when they put on the brakes.

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