A recent study from ACEEE showed that the Hummer makes more emissions than a Chevrolet Malibu. Mainly because of its size but also because of the U.S. power grid.

GM's response is that the Hummer is necessary to help win the public over to EVs.

I get where this study is coming from but the fact that the massive Hummer only produces the same amount of emissions as a mid-size sedan isn't as bad as I would've expected.

Researchers are calling the Hummer EV’s eco-friendliness into question, but General Motors says the research is missing the point. A study the ACEEE released in June claimed the Hummer EV has higher CO2 emissions than a Chevy Malibu. The electric Hummer’s upstream emissions are partially caused by fossil fuels in the U.S. power grid, but, mainly, because the Hummer EV is too big and heavy.

Now, GM has released a statement in response that says the study overlooks the value of the Hummer EV as a trojan horse to win hearts and minds in the U.S.:
The study ignores the real-world importance and benefit of bringing to market performance oriented EVs like the GMC Hummer EV [...] Seventy five percent of the tens of thousands of customers who’ve reserved a Hummer EV have never owned an EV – many are or were pickup owners. The GMC Hummer EV (and other performance-oriented EVs) are accomplishing more in bringing EV skeptics into the EV fold than any of these half-glass-empty criticisms ever will.
GM’s claim that the Hummer EV is helping convince buyers in the U.S. to go electric reads like an evasion. Or justification. It doesn’t address the criticism.

General Motors gave Robb Report and GM Authority the same statement, after they cast doubt on the Hummer EV as an environmentally-conscious vehicle. The term “eco-conscious” is implied in “EV,” but the study says that not all EVs are created equal. Indeed, EVs are far from being equally efficient, which is what researchers focused on.

This dirty power is kind of an open secret, and research shows that even in the dirtiest grid, EVs eventually produce less CO2 per mile than ICE-powered cars. The problem with the Hummer isn’t energy; it’s mass and energy conservation.

With efficiency as a metric, we can forget about the Malibu; we don’t have to compare EV and ICE, since the Hummer EV (341 grams) makes three times the upstream CO2 emissions of GM’s own Chevy Bolt EV (92 grams).

The Hummer EV is huge: it’s 18 feet long, 7.25 feet wide, and 6.5 feet tall. It weighs more than 9,000 pounds, and, yet, it goes from 0-60 in three seconds. That’s why GM calls it a “performance-oriented EV,” but the ACEEE finds it’d be better known as an inefficient EV. It burns comparatively more energy to cover its range, and it’s down to size and weight. Here’s the efficiency of a few EVs, according to the study, based on weight and measured in kilowatt-hours.