Heat pump water heaters – Game changers in efficiency



Published on April 26, 2020 |
by guest contributor

April 26, 2020 by Guest contributor

By Joe Wachunas, Solar Oregon

In order to make our homes money savers and climate champions, water heating has always been a stumbling block. While there are easy ways to use hot water efficiently (like the low-flow shower heads we presented in this Go Zero Hack), it is difficult to heat water without polluting.

The problem is that, until recently, heating something almost always meant burning something. And burning things creates pollution. Let’s call this dilemma the “heating conundrum”.

All types of heating, including water heating, face this conundrum. For example, most people today still use the first generation archaic technologies from our parents and grandparents. They use either:

  • Electric water heaters (40% of the market in the northwest United States (NW)), which consumes a lot of electricity, enough per year to allow my electric car to travel approximately 26,000 kilometers. In the past, much of this electricity was produced by burning fossil fuels, but that changes with electricity which becomes cleaner very quickly. However, typical electric water heaters remain very inefficient.
  • Gas water heater (33% of the NW market), in which gas is extracted from the ground (often in a polluting manner) and shipped to your home and burned. Only 50-60% of the energy used to heat water does this – the rest is wasted by ventilation.

About fifteen years ago, as climate change began to blow our necks, some intelligent people began to develop alternative water heating technologies to solve the heating conundrum. They created:

  • Instantaneous water heaters (13% of the NW market), which heats water on demand, only when you turn on the tap or shower. This makes instant water heaters very efficient because you don’t keep a 50-gallon water tank warm for the 23 hours a day you don’t use it. But most tankless water heaters still use gas, which means burning and polluting (just more efficiently).
  • Solar water heaters ((

So in summary, until recently, we have been stuck inefficiently burning things to heat our water.

A way out of the riddle

And then, in the last 5 to 10 years, a new kid has appeared – heat pump water heaters. Heat pump water heaters (HPWH) hold great promise in getting us out of the heating conundrum and becoming the 21st century water heating method.

New Kid on the Block – Heat pump water heater. Image courtesy Rheem.

They are crazy efficient. Heat pump water heaters are 7 times more efficient than gas and 3.5 times more efficient than electric water heaters.

How is it possible? Magic. Well, not really magic, but what seems magic. It’s the same magic that makes your fridge or air conditioner work – heat pump technology.

Heat pumps move heat from one place to another. They are so effective because they do not produce heat, but rather they move it from one place to another. As if by magic.

Small diagram on the operation of heat pump water heaters from energystar.gov

HPWH use electricity – Not only are they incredibly efficient, but heat pump water heaters use electricity, which gives us a recipe for heating clean water. Electricity is getting cleaner. We burn less and less and collect more electricity from the sun and wind. Renewable energy in the United States has doubled in the past 10 years, and the use of coal has been cut in half.

Electricity emissions have fallen off a cliff – exactly what we need them to do.

Heat pump water heaters are inexpensive to purchase or operate – Unlike solar hot water heating, heat pumps do not cost an arm and a leg. They cost a little more than gas or electric water heaters and there are often discounts that bring them to price parity. And because they use electricity so efficiently, it costs very little to operate. We are talking about $ 100 a year for the needs of an average family.

Average cost of operating a heat pump water heater.

My family story

Since we bought our house in 2012, my family has been using cleaner sources of energy for our house. We both want to save money and get as close to zero carbon as possible.

Changing all the systems in your house at the same time can be daunting, so we’ve done it in stages and saved one clean energy / energy efficient investment per year. For example, in 2012 we bought a set of solar panels. In 2013, we replaced our gas furnace with ductless heat pumps. In 2016, we obtained another set of solar panels to meet our increased electrical demand. In 2017, we bought a used Nissan Leaf (our first car, for only $ 7,500). In 2018, we purchased heat pump water heaters.

Our strange little triplex of a house.

The plural is correct because we replaced two water heaters – one in our main house, a 20-year-old gas beast and another in our secondary unit, which also supplied hot water to the radiant floor system.

The water heater in our garage was a lesson on frozen assets, something we invested in but that couldn’t be fully used because we bought the gas unit in 2012 and replaced it with the heat pump technology 6 years later. The world will likely have a large number of assets frozen during our transition to fully clean energy systems. In our case, as we gradually moved towards a clean energy house, gas hot water no longer made sense even if it was not yet at the end of its life.

My research on heat pump water heaters two years ago left me with a lot of questions since they were still fairly new to the market. Some recommendations emphasized that they should be placed in a garage or basement because they make noise and exhaust fresh air, effectively cooling the surrounding space. Our two existing water heaters were located in utility closets in the main living areas and we did not have a garage or basement to house the HPWH.

In short, after a lot of research and a little risk, we found that they are not noisy and do not cool the space much if they are properly channeled (ours escapes from the attic).

My HPWH extracts heat from the attic and expels cold air. Don’t judge the bad guys.

The success we have seen with these water heaters has followed a predictable and pleasantly surprising pattern for us. In our experience, when we went out on a branch and experimented with a new technology, or a lifestyle choice, for cleaner energy and our world, it always paid off.

And our water heaters have paid off. Over the course of a year, we replaced the two gas water heaters, an old one and a new one (ish), with heat pump water heaters. We have driven both in the attic, and on summer days they draw heat from the hottest place in our house and use it to heat our water (they also do it on winter days – As I’ve already said, Magic!). And they work like a dream. The HPWH of our house provides hot water for 3 showers and 6 people (our family of 4 people and our Airbnb unit), and that of the apartment heats the water for a shower, but also manages the heating system by the radiant floor which provides all space heating for the unit.

In my garage, the heat pump water heater also operates the radiant floor heating system.

And when the sun is shining and our solar panels collect photons to generate electricity, it is particularly satisfying to take a shower or operate the dishwasher, knowing that all the energy to heat the water comes from the Sun.

Heat pump water heaters have helped my family get out of the heating conundrum. We can have our cake and eat it too – all the hot water we need without polluting the earth, and save money by heating the water incredibly efficiently. These HPWHs ushered in an era of 21st century clean showers and baths and crockery for my family. Join us – the water is good.

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Keywords: Electric water heaters, Gas water heaters, Heat pump water heaters, Water heaters, solar water heaters, water heaters

About the Author

Guest contributor is made up of many people. We publish a number of expert guest posts in a wide variety of fields. This is our contributor account for these special people. :RE


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