State, provincial, municipal and in some cases national governments are declaring mandatory targets for 100% clean power. These regulatory targets are often considered renewable mandates as it is commonly understood that wind, solar, hydro and other renewable energy sources are needed to replace fossil-fuel power plants in a zero-carbon emissions future. 

According to the UCLA Luskin Center For Innovation November 2019 report of the Progress Toward 100% Clean Energy in Cities and States Across the U.S., more than 200 cities and counties, 11 states, Puerto Rico and the District of Columbia have 100% commitment or achievement.  More local and state governments are expected to follow. A growing number of investor owned utilities are making 100% commitments, whether the states they supply energy to mandate the requirement or not. Internationally countries such as Denmark and Scotland have officially committed to 100% renewable, many more nations are considering it, and the literature is full of a growing number of studies affirming that 100% renewable systems are cost effective and “doable”.

In most cases, the metrics that define “100%” compliance are often de-coupled from strict renewable requirements, quantified using metrics such as carbon intensity (e.g., 0 g/kWh of CO2 emissions), thus potentially allowing for nuclear and combustion of biofuels and synthetic renewable fuels to meet the goals. The terms 100% renewable, 100% carbon-free and 100% carbon-neutral are often used interchangeably.

Practically all of the targets (to date) have final implementation schedules in the 2040 to 2050 time frame, which are aligned with the International Panel on Climate Change (IPCC) reporting that in order to prevent negative impacts of anthropogenic climate change “Global net human-caused emissions of carbon dioxide would need to fall by about 45 percent from 2010 levels by 2030, reaching ‘net zero” around 2050”. Note that the IPCC recommendations refer to all human activity, including home heating and cooking, transportation and agriculture, while the majority of 100% renewable mandates apply only to electric utility systems. Electricity generation in the United States was responsible for approximately 30% of CO2 generation in 2017 (Fig.1-1). As other industrial sectors “decarbonize” they will become more reliant on utility infrastructure to supply carbon-free or carbon-neutral energy, in effect increasing utility load. 


Carbon sources by sector for the United States (2017)