The California Solar Initiative – Thermal Program is scheduled to sunset on July 31, 2020. At that time, no new residential, commercial or multifamily applications will be accepted. For questions about the incentive or application deadline, we encourage you to contact CSE’s solar thermal team via email.


Solar water heating is one of the best ways to save money on water heating, while drastically reducing your home’s or business’s carbon footprint and environmental impact.

Through the California Solar Initiative - Thermal Program, rebates are available for San Diego Gas & Electric customers who install solar water heating systems. The Center for Sustainable Energy manages the CSI-Thermal Program for the SDG&E service territory. This program is ratepayer funded and open to customers of the large California investor-owned utilities.

What is Solar Water Heating?

A solar water heating system captures the warmth of the sun and uses it to heat water for your home, business or multifamily property. Unlike solar photovoltaic (PV) systems that collect sunlight and convert it into electricity, solar water heating systems simply absorb the sun’s heat and transfer it to your hot water supply. With solar water heating, you can reduce your energy consumption and utility bills without sacrificing comfort or reliability – even on cloudy days and nights, the system works with your existing water heater so that you have hot water 24 hours a day, seven days a week.

How Does Solar Water Heating Work?

A solar water heating (SWH) system works in conjunction with your existing water heater or boiler to essentially preheat water before it enters the existing tank. Current systems can be used in conjunction with natural gas, electric or propane backup water heaters and boilers and even with tankless water heaters as long as the solar water heating system is compatible.

Inside Solar Thermal Systems

Solar collectors, typically mounted on your property's roof, absorb the sun's thermal energy.

A pump circulates a heat transfer fluid from the collectors through a heat exchanger in your solar storage tank.

The heat exchanger transfers the sun's warmth to your water supply.

Hot water flows to your existing water heater, which provides backup heating when the sun isn't shining.


Join CSE experts for a free workshop covering solar thermal technology, available rebates and more.

Register Today


Ready to install a solar hot water system? Search for licensed and eligible CSI-Thermal contractors in your area.

Find a Contractor