Originally Published: 10 AUG 22 16:33 ET

By Peter Valdes-Dapena, CNN Business

(CNN) -- General Motors is selling three years of OnStar service as a $1,500 "option" on all Buick and GMC vehicles, as well as on Cadillac Escalade SUVs. But this is an option you can't refuse.

A three-year OnStar subscription is now simply standard equipment on all these models, GM spokesman Patrick Sullivan said. But customers won't get their $1,500 back if they choose to decline the service, which they can still do.

OnStar provides emergency services contact, navigation assistance and other help to subscribers with the assistance of live operators. The electronic equipment required by the service is installed on most GM vehicles regardless of whether the buyer purchases a subscription. With a subscription, it can even be used to stop a stolen vehicle when requested by police. GM also now offers a version of the service that works with mobile phones and is not tied to a specific vehicle. The service has over 15 million subscribers in the US, according to GM.

Generally, purchasers of new GM vehicles are offered a free trial subscription. Buyers can then elect to subscribe to the service if they wished. Now, a three-year subscription is included with all GMC and Buick models and on Cadillac Escalades. While it's now standard, it's still listed as an option on the pricing documents for the vehicle and on the brands' websites. CNN Business' own attempts to de-select the OnStar option when pricing a Cadillac Escalade on the Cadillac.com website proved fruitless. The check-box for a three year OnStar subscription remained checked.

Most Buick, GMC and Escalade buyers choose to get an OnStar subscription anyway, Sullivan said, and making it standard was just simpler. He declined to say exactly what percentage of buyers voluntarily chose the service subscription except that it was more than half.

GM CEO Mary Barra has said that subscription services are expected to be a huge driver of revenue for the company in the future. GM also plans to offer subscriptions for services like the Super Cruise hands-free highway driving system and has even experimented with in-vehicle shopping.