By Nichola Groom

(Reuters) - Installing wind turbines and solar panels in the U.S. Midwest instead of other parts of the country would deliver the biggest cuts in climate-warming emissions and improvements in public health, according to a study published on Tuesday.

The magnitude of benefit from renewable energy depends in part on whether it is displacing coal-fired power plants or cleaner-burning fuels like natural gas, according to the study by researchers at the Harvard T.H. Chan School of Public Health and Carnegie Mellon University.

The size of the population and its proximity to power plants also matter when calculating the cost benefits of expanding clean energy, because of the impact on public health to removing pollution from the air, the study found.

The study found that a megawatt hour (Mwh) of wind-powered electricity installed in the Upper Midwest achieves about $113 worth of benefits compared with $28 per Mwh in California, which already boasts large amounts of renewables and gas. The values were similar for other renewable fuel sources, like solar.

"There's a lot of coal there and there's a lot of people who live in the region and downwind of the region," said Jonathan Buonocore, one of the study's authors, noting that some Midwest pollution travels to populations on the East Coast.

The study divided the nation into 10 regions, and the benefits of installing renewable energy were largest in the Upper Midwest, Great Lakes and Lower Midwest. The benefits were lowest in California, the Southwest and the Rocky Mountains.

Both the social cost of carbon - a measurement of the economic harm caused by carbon dioxide through its climate and other impacts - and lower mortality rates were factored into the cost benefit analyses, the study said.

The study did not include the impact of fugitive methane emissions from the natural gas supply chain, Buonocore said. Methane is a greenhouse gas more potent than carbon dioxide.

Carbon capture and sequestration technology on coal plants is about as cost-effective as renewable energy for reducing carbon emissions but less effective at yielding health benefits in most regions, the study found.

(Reporting by Nichola Groom; Editing by Cynthia Osterman)