So you want to get solar but haven’t heard much about solar hot water? If you’re a little confused on how this technology compares to photovoltaic (PV) systems, you’re not the only one.  Here are a few points to note:

• Solar water heaters, which make heat, cost significantly less than PV systems, which make electricity

• They offset a specific, smaller portion of your electricity bill, namely what you spend on heating water

• Federal, state, and utility level incentives will lower the costs of both solar hot water systems and PV systems

• The primary uses of energy within your building are the most important factors in deciding whether a solar water heater would be an effective investment.

Solar hot water systems are significantly more affordable than PV systems. Residential solar hot water systems usually cost $6,000-$8,000 after incentives, while PV systems could cost three to four times as much.

Solar hot water systems are designed to supplement conventional water heaters (powered by natural gas or by electricity), so they offset only the portion of your bill that comes from hot water demand. Since PV systems generate electricity, they can cover many other types of energy demands.

From an efficiency perspective, solar hot water technology is notable because it bypasses this step of electricity generation. Most of the time, accomplishing an end-use goal (like heating water) requires obtaining an energy resource (like oil, natural gas, or sunlight), converting it to an energy currency (like electricity) and finally using that currency to accomplish the end use goal. Solar water heaters avoid the middle “energy currency” step: they use the sun’s thermal energy to heat water directly.

As noted above, with the goal of minimizing overall energy use, the choice between solar PV and solar hot water depends on building energy use. All else equal, buildings that use a larger percentage of their electricity on hot water are better off with solar hot water systems. Facilities where this is particularly true include gyms, prisons, and some agricultural facilities. Buildings with low hot water demand, like offices, are much better served by PV.

Everyone’s situation is a little different when it comes to choosing the most effective home energy investments, but solar hot water is a great option that’s often overlooked.

Related, see this post from last year: Active Solar Water Heating vs. Passive Solar Water Heating.