Before revision:  A regulator imposes a floor on the amount of energy each regulated firm must generate from solar power in a given period , providing them with certificates for each generated MWh. Firms offset these certificates against the floor , paying a penalty for any lacking certificates.
After revision:  A regulator imposes a floor on the amount of energy each regulated firm must generate from solar power in a given period and provides them with certificates for each generated MWh. Firms offset these certificates against the floor , paying a penalty for any lacking certificates.