Light-emitting diode (LED) strips have recently become a top-rated light source, used primarily in interior lighting applications. This increase is mainly due to increased performance in technical parameters, primarily photopic luminous efficacy (PLE) and the CIE general colour rendering index (Ra). The relation between PLE and Ra was investigated for several types of light sources in the past and was found to be inversely related. However, confirming if a similar relation exists for the newest phosphor-converted LED strips based on up-to-date colour rendering metrics, such as TM-30-18 Rf (ANSI/IES), is essential. This study was based on measurements of 105 different phosphor-converted LED strips with correlated colour temperatures (CCTs) from 2500 K to 5000 K. The results showed that lower PLE and higher Ra usually characterize the group with lower CCTs than those with higher CCTs. In the group of LED strips below 3500 K, there is a strong negative linear correlation (R2 = 0.51, p < 0.001) between PLE and Ra. However, in the group with CCTs above 3500 K, the linear correlation between PLE and Ra is weaker (R2 = 0.29, p < 0.001). Moreover, the analysis of the relationship between PLE and TM-30-18 Rf showed no association between those variables. Results suggest the need to rethink the influence of PLE on colour rendering in the case of using modern metrics for LED lighting. Finally, the results are a reasonable basis for the further analysis of such associations, which should be done periodically according to the rapid development of LED light sources.
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