With technical assistance from the PV industry, Sandia National Laboratories has identified both best-practice elements and gaps that must be addressed to improve communication of equipment operational states and failure modes for the benefit of all parties to a PV operations and maintenance services contract. Sandia’s new report, “A Best Practice for Developing Availability Guarantee Language in (PV) O&M Agreements,” outlines an approach for developing new language for an equipment availability guarantee that is typically included in an O&M services agreement between a photovoltaic system or plant owner and an O&M services provider, or operator. This report analyzes language used in early PV availability guarantees and presents best practices and equations for more transparent communication about the reliability of the PV system and plant equipment as expressed in an availability guarantee. To that end, the paper reinforces the concept of tracking raw time-based availability, which is the equipment availability without any excluded events, and using it to inform and also compare to the contractual availability. The paper also discusses the concept of partial availability based on the degraded state of a certain piece of equipment, and presents the use of an irradiance-weighted availability which could incentivize O&M activities around minimizing the potential for lost energy production. The authors and the O&M working group participants offer improved guarantee language as a template for greater transparency, benefitting all parties in the O&M contract.