The guaranteed energy savings contract shall include a written guarantee of the qualified provider that either the energy or operational cost savings, or both, will meet or exceed within 20 years the costs of the energy conservation measures. The qualified provider shall reimburse the public university for any shortfall of guaranteed energy savings projected in the contract. A qualified provider shall provide a sufficient bond to the public university for the installation and the faithful performance of all the measures included in the contract. The guaranteed energy savings contract may provide for payments over a period of time, not to exceed 20 years from the date of final installation of the measures.