A year ago, Daimler had said its eActros could be ready for production in 2020.
Ten customers, including supermarket chain Edeka and logistics group Hermes, are to test Daimler's eActros truck this year, Daum said. After that, another set of customers will test it for another year.
Daimler and rivals including Tesla and Volkswagen's MAN are racing to bring electric trucks to market to cope with a push to shift from fossil fuels to greener vehicles and reduce pollution.
Daimler said it will invest 2.6 billion euros ($3.2 billion) in research and development at its trucks division through 2019, as part of a broader effort to mass produce electric heavy-duty commercial vehicles from 2021.
"In 2018 and 2019, Daimler Trucks will invest approximately 1.3 billion euros on average each year in research and development," Daimler said in a statement on Wednesday.
Daimler Trucks will focus on developing electric mobility, connectivity and automated driving technology for commercial vehicles, the company said.
Mercedes-Benz is testing trucks with 11 battery packs and two drive motors until 2020 to see if fully electric vehicles can replace diesel-powered equivalents, the company said.
Mercedes-Benz is testing two variants with a gross vehicle weight of 18 to 25 tons and will hand them over to a focus group of customers this year.
Reporting by Ilona Wissenbach