As with most green innovations, L&M also had the government on its side. The New York State Energy Research and Development Authority helped pay about half the $100,000 installation cost and will study the turbines’ efficacy.

For many sustainability advocates, that is precisely the issue. “A tiny windmill on a big building is just silly — it might as well be a pinwheel,” said Russell Unger, executive director of the Urban Green Council. “It’s a lovely idea, if people want to pay for it and test it out, but as far as return on investment goes, it’s a waste compared to more insulation and efficient building systems.”

L&M actually agrees. “We’re doing all we can to green the building, but it’s kind of hard to sell an apartment by showing people your high-tech boiler,” Mr. Dishy said. The three turbines should provide enough power, 12 kilowatts, to keep the lights on in all common areas, including the lobby, the hallways, the gym and a roof lounge from which the whirligigs can be seen.

What they do outside the building is even more important than what they do inside — the turbines are visible from the No. 7 train platform and the Long Island Expressway and surrounding streets. With dozens of towers on the rise in Long Island City, anything to help a project stand out is good.