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My sister is building a house in Ohio and I’ve been talking to her about how to make it green.Both she and my brother-in-law consider me an eco-zealot (which is arguably true, given the high tide and political risk), so when I make one of the many useful suggestions, it tends to draw attention.
For example, I suggested they install a central heat pump in place of inefficient resistance heating, but only after consulting their HVAC experts did they decide to install one (wow! They’ll save thousands of dollars and pounds of CO2 vs. the choice).They’re also getting their homes solar ready and plan to install panels in the coming years — mostly because solar provides a sense of self-reliance that’s always been popular across political and geographic borders.
However, when I tried to convince them to install a heat pump water heater, I ran into serious resistance.If you haven’t heard of heat pump water heaters, they are a very powerful energy/CO2 reduction technology hidden in the most humble appliance – the water heater.
Hot water accounts for 25% of household energy use, thus providing an opportunity to drastically reduce pollution and costs.I have installed 3 heat pump water heaters (in my house, an attached dwelling unit and a rental property), raved about them over the past few years, and recently started a new job at a national A nonprofit-led effort called the Advanced Hot Water Initiative 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 it.This creates barriers to adoption.
Of course, my sister and brother-in-law are interested in the fact that a heat pump water heater can save their family of 6 about $500 a year in electricity bills.But ultimately they cited their unfamiliarity with the technology and the fact that their trusted contractor in town hadn’t heard of them as reasons not to buy.Also, they plan to put the water heater in the closet in the first floor hall and don’t want to vent it outside (in some air conditioned spaces it’s better to have the heat pump water heater outside).In the end, they used an interesting argument that inspired me to write this article, along the lines of: “We’re going to install solar panels next year, so even if we use less efficient water heaters, that’s fine.”
This line of thinking got my wheels spinning.How many solar panels are needed to provide extra power to a resistance (aka typical old electric) water heater compared to a heat pump water heater?Would it be better to buy extra solar panels or a more efficient water heater?
To answer these questions, I first looked up 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 use 3,493 kWh (or $400), 4 times the electricity and cost of a heat pump.Of course, these are average numbers – my sister’s extended family’s savings are probably much higher.The difference between the two figures is 2,627 kWh, or about 25% of the electricity used by the average household.Therefore, using a heat pump water heater will reduce the electricity use of a typical home by about a quarter.Note that I’m not even discussing natural gas since we are working to eliminate 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 the additional 2,627 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 about $2.90 per watt of solar in the US, installing this additional solar would cost $6,380.
On the other hand, the average heat pump water heater costs about $1,400 (though you’ll find them cheaper, especially with rebates), which is about $800 more than a typical electric water heater.Spending a few hundred dollars more to install the water heater (otherwise a heat pump water heater would cost about as much as a standard electric water heater to install), and my rough calculations showed that the extra 7 solar panels my sister would need would cost 6 times the price of a heat pump water heater ($6,000 for panels, Water heater additional $1,000).
To me, it’s a testament to the enormous potential of these unsung heroes of heat pump water heaters.They save as much energy as 7 solar panels for a fraction of the cost.This exercise may also be useful for decision-making on other clean energy technologies.Solar power is still shiny, visible and exciting, and we should all be putting solar panels on our roofs whenever possible, but if you’re investing in climate impact, it’s worth considering the CO2 emissions.
Lessons learned here, next time you replace your old electric or fossil gas water heater, consider a heat pump water heater to go further with your clean energy and help save clean electricity from 7 solar panels, hopefully soon Power the rest of you to become an all-electric abode.
Joe lives in Portland, Oregon, and works for the New Building Institute, a nonprofit that promotes power and decarbonized buildings.He also volunteers with Electrify Now because he believes electrifying everything from transportation to homes is the fastest path to a fair, clean energy future.Of course, Joe and his family live in an all-electric house and drive an electric car.
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