It is no secret that natural gas and wind power are the cheapest sources for electricity generation in much of the U.S. But when accounting for local rules and availability, the picture of the lowest cost for new power generation in the U.S. becomes more nuanced, according to a new interdisciplinary study by the University of Texas at Austin.

The study began with the levelized cost of energy for each source, but then added in public health impacts and carbon emissions to calculate the "full cost of electricity." The study also accounted for costs and availability of each technology at the county level. It brought together researchers from UT’s Energy Institute, business school, mechanical and chemical engineering departments, school of public affairs and department of energy economics.

The high level results are not surprising. Without externalities, natural gas is the cheapest in much of the country, with wind dominating in the upper Midwest. Other studies, however, have found that the cost of utility-scale solar is well within the range of combined-cycle natural gas plants and wind power. Globally, Bloomberg New Energy Finance has found wind and solar will become the least-cost option in most regions within a decade. 

Add in externalities, and wind and natural gas are still the cheapest options, while coal and solar of all sizes cannot compete. The researchers included upstream, downstream and ongoing emissions as part of its life cycle emissions rates. Solar PV, for example, had the second highest upstream, one-time emissions rate due to its manufacturing process, but zero emissions once operational.

“We think our methodology is sound and hope it enhances constructive dialogue,” Joshua Rhodes, postdoctoral research fellow at the Energy Institute and lead author of the paper, said in a statement. “But we also know that cost factors change over time, and people disagree about whether to include some of them.”

There is huge variability in how emissions for solar manufacturing are calculated, even by studies that used PV systems in the same year, according to a recent study in Nature Communications. The clear trend, however, is a smaller greenhouse footprint than in the past for solar, according to the Nature study. The study noted that the greenhouse gas footprint for state-of-the-art monocrystalline silicon based PV systems is about half what it was a decade ago.

Utility-scale solar PV was notably absent from the first scenario in the UT study, but when the availability of each technology is assessed with county and local restrictions on siting being accounted for, the pictures becomes more complex.

In this scenario, nuclear and solar gain a foothold, with wind and natural gas combined cycle still the cheapest option for new power in most U.S. counties. Residential solar is attractive in pockets in Florida and Georgia and even upstate New York. Where wind resources are marginal and gas prices are high or pipelines don’t flow, nuclear often becomes the next best option.

The report is meant to inform local policy discussions, and also engage stakeholders to further the conversation. The project also comes with online calculators.

“We wanted to provide an opportunity for people to change these inputs,” said Rhodes, “and the tools we’ve created allow for that.”