I feel like there are lots of really exciting developments in this space, but they're practically all in the category of "maybe someday".

Another clever idea for reducing needless energy consumption, and in this case, deforestation.

Storing heat may be the last thing you think of when turning on an air conditioning unit, but one model takes advantage of the sweltering weather to heat water while cooling the air.

The aptly named Air Conditioner Water Heater, or ACWH, from Hotspot Energy has a condenser unit that sits outside of the building, collecting heat that the air conditioner compresses and expels from inside. The heat passes through a copper heat exchanger that connects to a home or building’s hot water tank. According to the company, the unit can cool a 1000-square-foot room and heat about 100 gallons of water per day. At its peak, the ACWH can provide 18,000 BTU, or 1.5 tons of cooling using 1333 watts per hour.

Heating water while cooling a building can help save energy, since the heat recovery process eases the load of the air conditioner. The unit has to be installed relatively close (ideally within 150 feet of) the water heater, however, and only heats water when the air conditioner is running and there is enough hot air to warm the water. Using the unit on a mild summer day won’t make a significant dent in water heating costs, but it could have an impact for homes with multiple residents who use hot water throughout the day to shower or wash dishes.

HotSpot Energy, which makes the ACWH, sees buildings as large solar thermal collectors, ripe for gathering heat. Although the unit can be installed anywhere, it was designed with the southern U.S. in mind, where many residents use air conditioners during spring and fall, in addition to summer. Commercially, the company envisions restaurant kitchens, laundromats and server rooms benefiting from their technology.

And since something like half of energy produced is lost to waste, simple conservation has a double impact. Save the energy you would have used, and you also save the energy you would have wasted.