The United States could shave as much as 28 percent off the amount of greenhouse gases it emits at fairly modest cost and with only small technology innovations, according to a new report.

A large share of the reductions could come from steps that would more than pay for themselves in lower energy bills for industries and individual consumers, the report said, adding that people should take those steps out of good sense regardless of how worried they might be about climate change. But that is unlikely to happen under present circumstances, said the authors, who are energy experts at McKinsey & Company, the consulting firm.

The report said the country was brimming with “negative cost opportunities” — potential changes in the lighting, heating and cooling of buildings, for example, that would reduce carbon dioxide emissions from the burning of fossil fuels even as they save money. “These types of savings have been around for 20 years,” said Jack Stephenson, a director of the study. But he said they still face tremendous barriers.

Among them is that equipment is often paid for by a landlord or a builder and chosen for its low initial cost. The cost of electricity or other fuels to operate the equipment is borne by a tenant or home buyer. That means the landlord or builder has no incentive to spend more upfront for efficient equipment, even though doing so would save a lot of money in the long run.