Solar-time reconstruction of electricity demand: A physical framework for peak shifts, daylight use and PV-load alignment

Abstract

The analysis of electricity demand is usually carried out in legal time, even though this may differ from real solar time due to time zones, geographic longitude, and daylight saving time (DST). This clock–Sun misalignment can distort the physical interpretation of hourly profiles, especially in regions with low solar variability and dominant evening peaks. This study develops a reproducible and physically grounded methodology to reconstruct the twelve monthly average days of 2023 for Gran Canaria in real solar time, applying the equation of time, longitude correction, and seasonal DST offset. All curves are projected onto a uniform 5‑minute grid, allowing coherent comparison between legal time and solar time representations. The results show: (i) a systematic but small shift of the daily peak (≈2–4 min) when expressed in solar time; (ii) a stable daytime energy distribution between 40% and 51%, indicating that social and circadian factors prevail over the solar cycle; (iii) a clear improvement in structural coincidence between demand and synthetic photovoltaic generation, with overlap indices ranging from 0.43 in winter to 0.55 at the beginning of summer; and (iv) partial adaptation scenarios (f = 0.2–0.4) that cause moderate peak advances of 10–25 min, far below the full 60‑minute shift associated with a complete legal change. These results provide a coherent physical framework to assess the impact of eliminating seasonal clock changes in subtropical regions. Beyond the case of the Canary Islands, the approach constitutes a generalizable tool to analyze demand-Sun alignment, estimate realistic social responses to time‑change policies, and support renewable integration strategies in systems with increasing photovoltaic penetration.