TDPUD's most recent official Renewable Portfolio Standard (RPS) is 60.3%. A utility’s RPS illustrates what percentage of its total energy purchases are from carbon-free and renewable resources. California's state mandate says utilities must be using 60% "renewable" energy by 2030 and 100% renewable and carbon-free by 2045. The California Energy Commission finalizes utilities’ official resource mix and RPS numbers annually at the end of the following calendar year, due to the complexity of the process. Currently, the most recent RPS figures we have are from calendar year 2023.

Different states have varying definitions of which energy sources qualify as “renewable.” California’s regulators have a strict definition of the term, so there are some carbon-free resources that do not qualify as renewable in their eyes, despite the fact that they do no burn fossil fuels and they achieve the goal of lowering greenhouse gas emissions from energy generation.

In 2023, TDPUD got 47.3% of its electricity from what California deems “eligible renewable” sources (biomass, small hydroelectric, solar and wind). This was much higher than the state average among all electric utilities, which was 36.9%.

TDPUD also gets power from other carbon-free resources that fall outside the state’s “eligible renewable” designation, like heat recovery and some large hydroelectric sources. In order to have an RPS that accurately reflects the carbon-free power sources that TDPUD utilizes, the utility purchases renewable energy credits (RECs). TDPUD purchases these credits to be able to properly account for the energy that it uses that is already renewable and carbon-free, but doesn’t meet the state regulator’s current requirements to be labeled renewable. The money used to purchase RECs goes to the carbon-free and renewable resource market, to continue to grow and invest in these technologies and increase availability, which furthers the ability for utilities to purchase affordable clean energy.

In FY23, 13% of TDPUD’s energy was covered by renewable energy credits (RECs), bringing the total RPS to 60.3% for that year. Having an accurate RPS is important because TDPUD needs to be able to paint a precise picture of its electric resource mix, and being at the forefront of the clean energy movement has ancillary benefits as well, such as favorable consideration by financial institutions for auditing and bond issuance.

TDPUD’s official 2023 RPS was finalized in November 2024. While 2023 saw the expiration of a landfill gas contract in TDPUD’s electric resource portfolio, it also increased its solar energy procurements due to the opening of Red Mesa Tapaha Solar Farm. Sourcing energy from a variety of resources is important to maintaining a reliable power supply. Carbon-free resources can be split into two categories: intermittent and dispatchable (also known as baseload). Intermittent electric resources are things like wind, solar and hydro, where output is determined by factors beyond human control, so it is impossible to predict exactly how much and when this energy will be produced. Dispatchable resources, like geothermal and biomass, will generate electricity as long as the power plant is operating, so they provide energy more consistently and are easier to plan around.

Current California legislation dictates that all utilities must have a Renewable Portfolio Standard of 60% by 2030, and requires all of the state’s electricity to come from carbon-free resources by 2045. TDPUD is well positioned today to meet the 60% target by 2030. TDPUD continues to increase the percentage of its electricity that comes from carbon-free resources, and its recently adopted Integrated Resource Plan (IRP) explores how best to match customer demand with clean, reliable, and affordable electric services.