Solar Hot Water Systems

Snapshot | Savings | How it works | Is solar for me? | Rebates | Take action!

Snapshot

Using the sun to heat hot water is one of the most effective ways to reduce your energy costs. The payback on an installed system can be as little as 8 to 10 years, depending on local rebates and water heating costs.

Sometimes called "solar thermal" and "solar domestic hot water" systems, a solar hot water system uses fluid-filled panels on your roof to capture the sun's heat and pipes the fluid into a heat exchanger in a tank, which is used to heat your home's water.

Solar hot water systems can be installed in both hot and cold climates. You're a prime candidate if your roof is exposed to the sun several hours a day. Solar thermal systems need less sunlight than electricity generating solar PV (photovoltaic) systems, and are more forgiving of shady spots.

Solar hot water systems must be tailored to the physical layout of your home and to your daily hot water needs. The products and technologies that are approved for federal and state rebates are all of very high quality. The details of installation of your solar hot water system will have a large impact on its performance. Be sure to use an experienced and qualified contractor. (Give Ennovationz a call. We can connect you to a qualified contractor in your area.)

Savings

The savings from solar hot water are immediate because the solar system replaces your natural gas or electricity use. Your savings potential equals your hot water spending. In the Bay Area, this typically ranges between $200 and $500 per year. A solar hot water system is sized to cover about 70% of that demand, so savings range from about $150 to $300 per year.

There are substantial federal tax credits for solar hot water systems, and California is launching a statewide subsidy program in mid-2010. This additional subsidy may be restricted to certain systems or installs after a set date, so it is probably worthwhile to wait a few months until the details are set.  Check back to this website, we'll be tracking the program announcements!

Solar hot water systems also qualify for PACE financing, the property tax based financing program such as CaliforniaFIRST, coming out in 2010 in many Bay Area counties. PACE will allow you to pay your solar hot water loan back through a small increase in your property taxes. Sonoma County residents can use the Sonoma County Energy Independence program, a PACE financing opportunity already underway. 

Solar hot water systems have two main components: 

 1. the solar collection panels and 

 2. the tank(s) to store the hot water. 

Typical installations have 1 to 3 panels, each about 8 to 10 square feet. The tank to store the hot water cannot be placed on the roof due to earthquake risk. 

One or two storage tanks, depending on the optimal arrangement of the heat exchangers for your system. These tanks are 2 to 3 times larger than a typical hot water heater, holding 60 to 120 gallons of water. Super-insulated, the tanks keep the water hot until you need it.

California regulations also require a backup water heating system, typically either a tankless hot water heater or boiler.  

The modern solar hot water system uses a pump to circulate a heat-absorbing liquid (such as glycol) through the panels and into the tank. Glycol or antifreeze is used in cold climates for winter protection. It is also a more efficient heating medium.

Solar hot water systems seldom fill all of your daily hot water needs. Here's why: In the summer, when sunlight is intense and plentiful, a smaller system is needed to meet the daily load. In the winter, a bigger system is needed. The result? A tendency to install too much capacity for summer needs. But, a system with too much capacity pumps the fluids very slowly through the panels, causing problems in the summer. The compromise between too much physical capacity and a minimum summer flow rate determines the size of your system. In the Bay Area, a typical solar hot water system is sized to provide about 70% of your daily needs. 

Simple diagram of a typical solar hot water heating system. Graphic: U.S. Department of Energy

Is solar hot water right for me?

The best time to consider a solar hot water system is when you are replacing your water heater. It is difficult and more expensive to add a solar thermal system to an existing water heater. (But we are always looking for that simple technology add-on!) The typical life of a standard water heater is 9 to 10 years, so if your unit is more than 8 years old, now is a good time to explore solar hot water.

A key factor in your decision will be the available roof area. Best is south and southwest facing, with plentiful sunshine. Some shading can work, so even if your roof area is not suitable for solar PV, it may be just fine for solar hot water.

Make sure to use a qualified and experienced contractor. They can help you evaluate your roof area and size the system to your home. Working with a good installer is the number one thing you can do to get great results from your solar system, so make sure the contractor you use has good local references. 

Finally, the state of California is launching a $350 million solar hot water subsidy program in mid-2010. It might be worthwhile to wait until the program details are known before installing a system. You might save hundreds of dollars, perhaps even $1,000 or more! 
 

Rebates

Federal: Federal tax credits up to $1,500 are available. Details here.

State: The California state program will launch in 2010. Check back for details. 

Local:

City of Palo Alto Utilities: Rebates of up $1,500. Details here

Sonoma County:  Use PACE financing to ease the cost of solar hot water. Details here.

Take Action!

Install a solar hot water system