How do you know if you’re getting a good deal on a hotel room? Well, a new Web service plans to tell you.

Travel search newcomer Farecast.com, which makes predictions on the rise or fall of air fares, launched a new hotel search service on Wednesday that tells users whether the rate for a particular property is a good one.

Hotel rates can vary widely, affected by local events like weddings or conferences as well as broader travel trends like winter weather.

Also, all hotels are not created equal, with location and amenities affecting rates.

“The supply-and-demand characteristics of a hotel room are very unique,” Hugh Crean, the site’s president and chief executive, said in an interview.

“Prices do meaningfully change week to week.”