Solar hot water heater on a Jamul rooftop. Photo taken by Chris Wilder of Solar Services of San Diego, Inc.
Solar hot water on a Jamul rooftop. Chris Wilder, Solar Services of San Diego, Inc.

Nearly 40 years after California began offering inducements to people to heat their shower water using the sun, Brad Heavner of the California Solar Energy Industries Association still has to remind them the technology even exists.

News in Numbers

When most people think about solar energy, they think about solar photovoltaic panels that make electricity. “But there’s also solar water heating systems that are very effective at using energy from the sun,” Heavner said.

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Panels that heat water are not sparkle blue. Instead, they are often a dull black inside. It’s all about absorption. And they are larger than panels for electricity.

This clickable map shows just how few San Diego County residents are opting to install the systems, even if they are cheaper than solar electricity.

A data set obtained from the state shows fewer than 500 solar hot water systems installed since 2010. The systems vary, but here is one scenario for how they work on a single-family house:

Say you have a gas water heater. A contractor will install one or two water heating panels on the roof, plus an 80-gallon tank next to your water heater. Now the sun will preheat the water on the roof before it flows into your existing water heater. That means the gas doesn’t turn on nearly as often.

Chris Wilder is president of Solar Services of San Diego Inc., which the data indicates has installed more residential systems locally than any other company in the past six years. He said the average total cost for a house installation is $6,000 to $8,000. California rebates $1,500 to $3,000 on the cost of each system. Wilder said his own summer gas bill dropped to $5 to $12 a month when he installed his.

If instead of gas you have an electric hot water heater, the solar setup can be simpler. Your existing water heater is removed altogether, and a tank of solar hot water, assisted by an electric coil, is installed on the roof.  Currently there are no rebates for people with that sort of system, so homeowners pay full cost.

Cost is no doubt one deterrent hurting sales, but Wilder, like Heavner, said many people are just unaware of the possibility. “There are more people marketing solar electricity than marketing solar hot water,” he said.

Many of the solar hot water installations in San Diego County sit on apartment buildings and condos. The data show Adroit Energy Inc. did the largest number of those installations. People may be more familiar with solar pool heating. The data set shows California Solar Thermal Inc. was the most prolific installer of those.

The state data comes from the California Solar Initiative. Building owners who installed systems but didn’t request a rebate might not show up in the data. Heavner, however, said he thinks most owners do pursue the rebate.

Ingrid Lobet is a reporter at inewsource specializing in the environment. To contact her with tips, suggestions or corrections, please email

5 replies on “Sun shines in San Diego, but few install solar hot water”

  1. This is purely an issue of economics. The turnaround cost on solar is in the 8 – 10 year range. The turnaround cost on these devices looks closer to 47 years if the data in this article is vaguely accurate. The only numbers offered here are from a person quoted who owns a company that sells these devices, but let’s take averages based on his assertions. If the cost of installation is $7,000 and the rebate is $2,250 then the net cost is $4,750. If the savings per month is $8.50, then the savings per year is $102. At that rate, it would take 47 years to pay off the device. (Who expects to live in their home that long?) That assumes that the device needs no maintenance, which is unlikely. It also assumes the numbers from the salesman are correct. There’s also the fact that this is one more rooftop installation that may cause problems. But here’s the real kicker: If you invest $4,750 and can achieve a long-term return of 4%, you would have roughly double the return on your investment compared to the solar water heater without the maintenance worries and related issues. Bottom line: Looks to me like these devices are a bad investment, and that’s from someone with solar that is penciling out nicely.

  2. Hi BC, thank you for the thoughtful reply. I think the savings per month can be considerably more than $8.50/month. I don’t think the (admittedly brief) article says the savings is $8.50/month. These News In Numbers stories are a new idea we are trying. They’re intended to be a peak into public data sets, with the notion that we paid for the data and it may contain interesting information. But we’re open to critique, and the idea may not work. The format may just be too abbreviated.

  3. Ms. Lobet: Thanks for this. The business owner you quoted said his own summer gas bill dropped to $5 to $12 a month when he installed his. I just took the middle of that. I doubt his experience is representative, but absent anything else I used it as a ballpark. My personal gas bill suggests to me that heating water costs somewhere around $2 – $3 per person per month, but that is very ballpark too. I think though that the overall math is probably correct in the sense that these devices are not cost effective for most homeowners. That may be the bigger story: That people aren’t doing this because it doesn’t save money.

  4. Just to clarify, Wilder said his bill dropped to this amount, not by this amount.

  5. Ms. Lobet: Thanks for the correction. You’re obviously right. I should have read more carefully. Sadly however, that makes the information provided in the quote entirely useless without any information about what his bill was previously. I wonder why inewsource would report something that lacks any context.

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