A key element of evaluation, measurement, and verification (EM&V) studies for energy efficiency programs involves estimation of net energy savings that account for free ridership, spillover, and induced market effects. The existing literature recognizes these effects to be significant and provides detailed guidelines to estimate them. However, there appears to be a disconnect between these guidelines and field evaluations conducted in practice. Our meta-analysis of 120 studies from 2006 to 2018 indicates that most free ridership and spillover estimates are based on survey results and expressed in percentage terms. We note that simply adding these percentages numerically without converting them into a common unit is inaccurate and obscures a program’s true impact. Additionally, there exists wide variations in nomenclature, classification, and methodologies adopted to estimate these metrics across programs and jurisdictions. Our scatterplot analysis of the reviewed EM&V reports indicates that with few exceptions, free ridership and spillover do not necessarily offset each other. We propose an alternative approach to estimate free ridership and spillover in energy units with costs in dollar terms, e.g., as the difference between a program participant’s total willingness-to-pay and the total financial impact of the program’s existence. We also feel that a consistent, transparent, and reliable evaluation methodology to estimate free ridership and spillover effects across programs and jurisdictions based on randomized or quasi-experimental designs will not only improve accuracy but will also have better comparability for informed policy decisions in future.

中文翻译：

---

不加总：能效评估中的搭便车和溢出计算

能源效率计划的评估，测量和验证（EM＆V）研究的关键要素包括估算净节能量，这是搭便车，溢出和诱发的市场影响的原因。现有文献认识到这些影响非常重要，并提供了详细的准则来估计它们。但是，这些准则与实践中进行的现场评估之间似乎存在脱节。我们对2006年至2018年间120项研究的荟萃分析表明，大多数搭便车和溢出估计是基于调查结果并以百分比表示。我们注意到，简单地将这些百分比数字化地添加而不将其转换为通用单位是不准确的，并且掩盖了程序的真正影响。此外，术语，分类，以及用来估算跨计划和辖区的这些指标的方法。我们对经审核的EM＆V报告的散点图分析表明，除少数例外，搭便车和溢出不一定相互抵消。我们提出了另一种方法来估算能源单位中的搭便车和溢价，其成本以美元为单位，例如，计划参与者的总付款意愿与该计划存在的总财务影响之间的差额。我们还认为，基于随机或准实验设计来评估跨计划和辖区的搭便车和溢出效应的一致，透明和可靠的评估方法不仅可以提高准确性，而且在未来的明智决策中具有更好的可比性。