Solar in Palo Alto

 ""  

Solar energy is a clean, renewable resource that can efficiently heat water and provide electric power. The City of Palo Alto Utilities (CPAU) offers a variety of informative resources to residents and businesses interested in solar energy.

Background and Benefits

About a third of Palo Alto's electricity demand is met by utility-scale solar and 100 percent of Palo Alto's annual electricity demand is met by carbon neutral supply, meaning supply that is sourced from renewable or hydroelectric sources. Residential and commercial customers may still want to consider going solar. 

How a Grid-Tied Rooftop Solar System Works

Electricity generated by rooftop solar powers your home the same way that electricity coming from the grid does.  First, a rooftop solar system converts sunlight into direct current (DC) electricity.  An inverter then converts DC electricity from your solar panels into alternating current (AC) electricity, the type of electricity used by appliances, lights and other devices in your home. Your home's main electric panel connects power supplies — such as rooftop solar and the utility grid — to circuits in your home. Those circuits include outlets that you can plug appliances and devices into, as well as switches that you can use to direct electricity where you need it. Your utility meter measures electricity that flows between your electric panel and the grid. The type of meter you have depends on which Net Energy Metering (NEM) program you are served by. Your utility, City of Palo Alto Utilities (CPAU), provides electricity from the grid when your solar panels do not produce enough to meet your needs and compensates you for excess electricity that you export to the grid when your system generates more than you are using.

Solar Resiliency and Battery Storage

A standard grid-tied rooftop solar system will not provide electric power to your home in the case of a power outage. All grid-tied solar systems are required to disconnect from the grid during a power outage. This is so the “mini power plant” on your roof doesn't feed electricity back into the grid during an outage, which would endanger utility workers who are repairing the utility wires.
 
Rooftop solar with a battery can provide back-up power during an outage if the battery is wired properly. A battery storage system can allow you to capture unused power from your solar system and draw on that power during an outage event. Any solar and/or backup power systems must have a manual disconnect switch so that utility workers can disconnect the home from the grid in order to repair utility lines safely. Customers planning on installing a backup power system can learn more about Palo Alto battery storage permitting and inspection requirements by reviewing the Energy Storage System Permitting Checklist(PDF, 1MB). If you want to set up your battery storage system to function during an outage, be sure that your installer follows the appropriate requirements laid out in the permitting checklist.

Often, homes with battery storage will install a critical-loads subpanel because their backup power system was not sized to power the entire house but only the essential appliances, such as lights and refrigerators. The subpanel allows these critical loads to be isolated and the backup power supplied to only these loads.

*Specialized islanding solar inverters are also available, which can enable solar panel function in an outage without a battery. Islanding inverters can generally only provide reliable power equal to about a third of the home’s solar capacity, so a critical-loads subpanel would still help provide the best customer experience.

**Limited backup power can also be supplied by a solar generator, which can be used to power a few essential appliances, such as medical equipment, during an outage. These generators work by charging a portable battery with a small, portable array of solar panels.

Limited Time Discounts for Solar and Battery Storage

Residents can sign up for the SunShares group-buy program and receive discounts on solar and battery storage installations. Visit our SunShares page to learn more.