Use of vacuum-insulated tubing (VIT) in thermal (typically steam injection) wellbores dates back to at least the 1980s but, due to high cost and limited availability, its use until recently had been limited. While it has the potential to significantly reduce heat losses to overburden, thereby improving well operating economics, the correct application of VIT can be more of an art rather than science given the factors that impact its performance. These include understanding how VIT is manufactured and what design elements influence good long-term performance, what quality assurance is used during manufacture and on the finished product, how to confirm actual k-factor (insulation) values on delivered product in lieu of advertised values, and how to verify true performance once the VIT is installed in a well. Recent new global sources of VIT have provided additional product choices for operators, as well as more competitive pricing, allowing VIT to be more broadly considered in projects where downhole heat losses must be actively managed to achieve the recovery performance desired. Calculation of heat loss reduction can be done with several different programs, but careful attention must be paid to the way the computer model is built to ensure results reflect actual, expected, field conditions.