Renting or leasing services of machinery and equipment including generators fall under SAC (Service Accounting Code) heading 9973. This heading covers leasing or rental services with or without an operator.
Here is a description:
99: Services
73: Leasing or rental services with or without an operator
Specifically, generator rental services can be classified under:
9973.12: Leasing or rental services relating to machinery and equipment with or without an operator.
For GST purposes in India, the GST rate for services classified under SAC code 9973.12, including generator rental services, is generally 18%.