Employment of precise positioning techniques will enable low-cost receivers for a variety of applications. The complexity of techniques such as Precise Point Positioning (PPP), or differential techniques that require the use of external sources of corrections, could be a disadvantage for users. On the other hand, a simple technique such as Single-Point Positioning (SPP) alone does not provide high-level accuracy. Nevertheless, the entry Galileo High-Accuracy Service (HAS), even if developed to be applied on PPP, could offer a positive impact on SPP. The objective of this study is the analysis of the effects of HAS on SPP, which are evaluated for Galileo and GPS, in single- and double-constellation mode. Results are encouraging, especially on the vertical channel, where some centimetric improvements are obtained.