Technical Reference Manuals (TRMs) are used across the nation to support utility program design with guidance on potential savings and impacts. TRMs are intended to be a consistent and reliable source for calculating energy impact savings – both per energy efficiency measure as well as for demand savings. However, it is important to understand the potential inaccuracies of these models because they are used extensively to predict energy savings, report to regulators, identify cost-effective programs and measures, and compare programs. The savings estimates are critical because they may affect program measure selection, program funding, or even whether or not a program is continued. The session will provide examples of how and where TRMs have gone wrong, where additional analysis methods are needed, and how TRMs can most effectively be used. Presentations will include analyses of TRM challenges and inaccuracies, examination of specific impacts of partially deemed savings calculations in measure selection, and opportunities for standardized simulations to expand the range of measures offered, calculate accurate demand impacts, and optimize both project and program design. Participants will also hear about how to influence and improve local TRMs.