In the quest to achieve a net-neutral climate impact, many companies seek to buy additional power from clean energy sources in an attempt to eliminate the emissions otherwise generated by operating on today’s fossil fuel-heavy grid.

Yet some of the most common strategies for purchasing clean energy have little impact in cutting long-term carbon emissions in the United States, a Princeton-led study has found. However, one approach, in which companies purchase clean energy hourly to match their real-time energy consumption, can have a substantial effect.

The approach, known as temporal matching, hourly matching, or 24/7 carbon-free electricity procurement, was the only strategy that consistently lowered system-wide emissions among those studied by the Princeton team, whose analysis was published January 11 in Joule.

“Achieving an around-the-clock 100% clean power system is difficult. It will take a lot of time and money,” said Wilson Ricks, study coauthor and graduate student in mechanical and aerospace engineering. “The idea that a company could come in and claim to be 100% clean in 2024 at no additional cost premium sounds a little suspect, as do the emissions accounting schemes that would enable that to happen. If it were that easy to decarbonize the world, the problem would already be solved.”