For example, I suggested they install a central heat pump instead of inefficient resistance heating, but it wasn’t until after consulting with their HVAC experts and being heat pump fans that they decided to install one (wow! They would save thousands of dollars and pounds of CO2 with that option). They are also preparing their homes for solar energy and plan to install panels in the next few years – mainly because solar energy gives a sense of self-confidence that has always been popular regardless of political and geographical boundaries.
However, when I tried to convince them to install a heat pump water heater, I ran into a lot of resistance. If you haven’t heard of heat pump water heaters yet, they are a very powerful energy/CO2 reduction technology hidden in the most inconspicuous device – the water heater.
Hot water accounts for 25% of household energy consumption, offering the opportunity to drastically reduce pollution and costs. I have installed 3 heat pump water heaters (in my house, attached living space and rental unit), have been delighted with them over the past few years and recently got a new job with a national non-profit organization called Advanced Hot. The Water Program aims to have every new water heater using heat pump technology by 2030.
Heat pump water heaters use technology similar to refrigerators or air conditioners to move heat rather than generate it, and are more efficient than 20th century gas and electric resistance water heaters. Heat pump water heaters make up about 20% of new water heater sales in my state of Oregon and about 60% in Maine, but in many places people haven’t heard of them. This creates barriers to acceptance.
Of course, my sister and son-in-law are interested in the fact that a heat pump water heater can save their family of 6 about $500 a year on their energy bills. But in the end, they cited their lack of knowledge of the technology and the fact that their trusted contractor in the city hadn’t heard of them as reasons why they didn’t buy. Also, they plan to put the water heater in a closet in the ground floor lobby and don’t want to bring it outside (in some air-conditioned spaces it is better to have the heat pump water heater outside). In the end, they used an interesting argument that inspired me to write this article: “We are going to install solar panels next year, so even if we use less efficient water heaters, it’s okay.”
This train of thought made me dizzy. How many solar panels do you need to provide extra power to a resistive (aka typical old electric) water heater compared to a heat pump water heater? Which is better to buy additional solar panels or a more efficient water heater?
To answer these questions, I first found a 50 gallon heat pump water heater and compared it to an electric water heater from the same manufacturer (Rheem in this case). According to Energy Star, a heat pump water heater uses 866 kilowatt-hours (or $100) of electricity to produce all the hot water a home needs for a year. A resistance water heater will consume 3,493 kWh (or $400), which is 4 times the electricity and cost of a heat pump. Of course, these are averages – my sister’s extended family’s savings are probably much higher. The difference between the two figures is 2627 kWh, or about 25% of the electricity consumed by the average household. Therefore, using a heat pump water heater will cut the electricity consumption of a typical home by about a quarter. Note that I am not even discussing natural gas as we are working to move away from fossil fuels and heat pump water heaters are 4-6 times more efficient than gas water heaters.
In order for the resistance water heater to use an additional 2627 kWh, my sister needs an additional 2.2 kW of solar energy, which is equivalent to about 7 solar panels. With an average cost of around $2.90 per watt of solar power in the US, installing this additional solar power would cost $6,380.
On the other hand, heat pump water heaters cost around $1,400 on average (although you’ll find them cheaper, especially with discounts), which is about $800 more than a regular electric water heater. Spending a few hundred more dollars to install a water heater (otherwise installing a heat pump water heater would cost about the same as installing a standard electric water heater) and my rough calculations showed that the extra 7 solar panels my sister would need would cost 6 times more expensive than a heat pump water heater ($6,000 for panels, water heater an additional $1,000).