## C5 Rooftop Solar Vs Utility-Scale System

Question

The larger utility-scale PV systems cost about half as much as onsite PV systems. Would it be more cost-effective to achieve the state’s policy goals with the less expensive utility-scale PV systems?

Answer

The state is pursuing a diverse set of energy and environmental policies to simultaneously save energy and reduce greenhouse gas emissions, including:

• Reducing greenhouse gas emissions from all sectors, including buildings and transportation.

• Maintaining grid reliability and resilience.

• Achieving cost-effective energy savings in buildings.

To achieve these policy goals, the state must use all available options, including utility-scale and onsite PV systems. These approaches are complementary and not mutually exclusive. Both options reduce carbon dioxide (CO2) emissions, and present unique opportunities, challenges, and environmental benefits:

• Utility-scale PV systems may be up to 500 megawatts (MW) or larger. The benefits include installed equipment costs that are less expensive per watt ($1.05 to $1.20 per watt) than an onsite rooftop system, and reduced system-wide CO2 emissions. The challenges include acquiring large plots of land, long transmission, distribution, and transformer infrastructure; and time consuming, and expensive environmental impact reports. The systems can also negatively impact sensitive wildlife habitats. It is important to include all costs and challenges when comparing a utility-scale PV system to onsite solar.

• Onsite or rooftop PV systems are generally only a few kW. The installed equipment costs are around $3 per watt. The benefits of these systems are that they do contribute to CO2 reduction from building loads, they do not require land acquisition (the roof is existing and available for PV deployment at no additional cost) or additional transmission and distribution infrastructure because the system is close to the load it serves. As part of a local distributed energy resource (DER) system and because of the proximity to the loads it serves, an onsite PV system, once coupled with smart inverters, demand response, and a battery storage system, can enhance grid reliability and resilience. The benefits of a DER system include providing ancillary services (frequency and voltage regulation) and improved reliability during grid failures, natural disasters, and wildfires. Further, the distributed nature of small generation systems reduces the grid’s overall vulnerability to cyberattacks. Onsite efficiency and PV systems allow building occupants to save each month on their utility bills, making home ownership more affordable.

Importantly, the 2019 Standards allow community-scale PV as an alternative renewable resource to onsite PV systems, when approved by the Energy Commission. Community-scale PV systems can range from a few kW to a few MW. The equipment costs for these systems are even lower than rooftop, in the $2-per-watt range. Plans for community solar may face unique barriers such as limitations of the compensation model. Some community solar options may also require land acquisition, and distribution infrastructure development.