OPEX is different from CAPEX because in opex the payments has been done on monthly basis but in CAPEX it work on annual basis.Under OPEX developer finances, installs, operates and maintains the rooftop solar power plant. The developer signs an agreement with rooftop owner. The rooftop owner consumes the electricity generated, for which they have to pay a pre-decided tariff to OPEX developer on monthly basis for the tenure of the agreement.