PORTLAND — The city has picked a local company to negotiate its electricity and natural gas contracts.

Competitive Energy Services, headquartered in Portland, will monitor energy markets for the city and negotiate the contracts. The firm was picked after a competitive bidding process.

CES is an energy consulting service that works for a variety of public and private sector clients around the country.

Ian Houseseal, Portland’s sustainability coordinator, said a consultant can keep a closer eye and have a better sense of the trends in energy markets than the city could itself and will recommend the best time to buy contracts with electricity and natural gas suppliers.

CES is paid per kilowatt hour and per therm – a measure of natural gas consumption – for the contracts it negotiates, Houseseal said. The city estimates that the company will earn about $19,000 a year for negotiating electricity contracts and about $11,000 a year for the natural gas contracts.

The contract calls for CES to arrange suppliers for gas and electricity for all city buildings and services, such as streetlights.