Remember the days when solar panels on roofs were a novelty? Today, they're a familiar sight, harnessing the sun's energy for electricity. But what about another solar technology – the humble solar water heater? Once a symbol of eco-consciousness in the 1980s, it faded into obscurity. Now, whispers of a comeback are stirring, fueled by rising energy costs, environmental concerns, and a government nudge.
My dad, a pioneer in green living, proudly installed a solar panel on our Florida roof back then. It looked like a portal to a future powered by the sun. Heating water to a scorching 180 degrees Fahrenheit, it served our family of four well. "We had no trouble," he reminisces, "and it was still working when we sold the house."
Fast forward to today, and you'd be hard-pressed to find someone using these heaters, while photovoltaic panels grace millions of American homes. The reason? Photovoltaics generate electricity, powering entire homes, while solar water heaters focus solely on heating water. However, they boast impressive efficiency, converting 60-70% of the sun's energy into heat, compared to 24% for photovoltaics.
A new generation of manufacturers, armed with subsidies from the Inflation Reduction Act and the allure of net-zero emissions, is betting on a solar water heater revival. The potential is undeniable: almost 20% of American home energy goes towards heating water, with solar offering a significant carbon footprint reduction. The EPA estimates an average household could save 2 tons of CO2 annually, equivalent to taking your car off the road for four months!
Solar water heaters have remained largely unchanged since their 1909 debut. These simple systems, made primarily of copper, aluminum, and glass, can heat water to 180 degrees Fahrenheit, with backup gas or electric elements for additional heating.
Several factors: unskilled installers, shoddy designs, plummeting natural gas prices, and the critical end of federal tax incentives in the 1980s. By 1990, the industry had nearly vanished. Today, only around 370,000 systems operate in the US, mainly on larger buildings.
Wherever the sun shines, these collectors work well. Countries with high energy costs, like Israel and Hawaii, have embraced them. In fact, almost all new residential buildings in Israel require solar thermal! Even in Canada and Denmark, where sunshine is scarce, district heating systems powered by solar thermal warm millions of homes.
Despite its potential, solar thermal remains a niche player, supplying a mere 0.4% of global domestic hot water demand. As SunEarth's president, Adam Chrisman, puts it, "It's always been about money." Where energy costs are high, the market thrives.
Take Hawaii, where imported fossil fuels power electricity, and retail prices are triple the US average. With constant sunshine, 25% of single-family homes now use solar water heaters.
However, in the US, with relatively low energy prices, solar thermal struggles to compete, even with incentives. Martin Morehouse, a developer with extensive experience, notes the shift towards commercial applications due to economies of scale.
While photovoltaics and heat pumps have become cheaper, solar thermal prices haven't fallen as dramatically. This, combined with rising copper costs, makes photovoltaics the more economical option for most single-family homes.
It's not a simple yes or no. While the US enjoys abundant cheap gas, factors like unreliable grids and climate change costs become more relevant. As Chrisman says, "You're buying energy security for the future."
