Fifty-seven million tonnes a year
When wind, solar and storage can connect faster and their power can travel to the next region, gas plants run less. The modelling finds 71 million tonnes less carbon dioxide in 2035 in the four regions it covers, nine percent of their power sector emissions. Across the country and across a decade in which the lines arrive gradually, that averages about 57 million tonnes a year.
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Value
The stream is carbon dioxide not emitted from American power plants [1][2]. Its harm falls on people everywhere and for generations, not on those who use the electricity, which places it with the broad environmental goods on this scale. A tonne is priced at the cost of avoiding it elsewhere, which keeps the climate argument on the same footing as every other climate debate on this site. The local air pollution from the same chimneys is a different harm, to different people, and is counted separately in the next argument. The emissions that the bill may add through faster gas pipelines are counted against it on the other side, not netted here. The value is in the upper middle of the scale: a broad environmental good, priced at what it costs to secure it another way.
Impact
The modelling finds 71 million tonnes less carbon dioxide in 2035 in the four regions, a nine percent cut in their power sector emissions, as solar rises 22 percent, wind 14 percent and storage 65 percent against the business-as-usual case [1][2]. Scaled to the country outside Texas by the same factor of 1.6 that the modellers' national cost total implies, that is 114 million tonnes in 2035, with 1.0 as the floor [1][2]. Because the lines and the faster queue take effect from 2029 and rise to the 2035 level, the average over 2027 to 2036 is half the 2035 figure, in a range from three tenths to seven tenths [4]. That gives 57 million tonnes a year, in a range from 21 to 80 million. An earlier estimate for the transmission provisions of the 2024 permitting bill found 6.5 billion tonnes avoided through 2050; read as a straight ramp, that is in the same order of magnitude, but it was made under the tax credits for clean power that Congress has since ended, and by an organisation that campaigned for that bill [7]. Priced at the cost of avoiding a tonne elsewhere, the result is a Normalised Impact of 5.68 on the scale of this evaluation, in a range from 2.1 to 8.0. For scale, American power plants emitted 1,485 million tonnes in 2025. The Impact is the largest real effect in this debate and depends on how fast regions actually build the lines.
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Plausibility
The counterfactual is the same business-as-usual case as for the cost saving: today's queue completion rates and no new interregional lines [2]. The design is a capacity-expansion projection with GenX, so the tonnes follow from modelled dispatch, not from a measured change [2]. Nobody has modelled the bill as introduced: the projection covers two reforms the bill contains and names no bill, and the earlier estimate for the 2024 bill assumed tax credits that no longer exist, so it supports the direction and little more [1][7]. The queue reform and the federal power to approve stalled lines follow from the text; whether regions then build the interregional lines the model assumes is not covered by anything [4]. The confounder that matters is the same as for the cost saving: if wind permits stay slowed, part of the new transmission carries less clean power [3][16]. Reverse causation does not arise. A climate scientist who reviewed the deal expects it to lower emissions on balance, with the fossil fuel provisions acting at once and the clean power gains only after some years [17]. Read as a statement about the world: a little under half of the modelled tonnes can be counted on within the decade. The Plausibility matches the cost saving, because both are the same modelled build seen from two sides.
Open: An independent model of the bill as introduced, under today's tax law, would replace the transfer from two modelled reforms and could lift the plausibility to the projection ceiling of 6.0.