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The increasing occurrence of near-zero or negative electricity prices, particularly in regions with high photovoltaic penetration, reduces the attractiveness of photovoltaic-based self-supply systems. This study evaluates the cost-effectiveness of photovoltaic-battery energy storage systems for self-supply under different electricity market conditions (Sardinia, Spain, and Germany), technology cost levels, load profiles (office, hotel, residential), photovoltaic sizes (100–1000 kW), and storage capacities (0−2 h ). The analysis is based on real hourly load profiles and market prices. In low-price markets such as Spain and Germany, many configurations are not economically viable compared to grid purchases. Median savings are close to zero, and several setups yield negative returns. In contrast, Sardinia exhibits average savings of 21.4 %, with peaks exceeding 40 %. Across all locations, larger PV systems and minimal storage provide the highest savings, while maximizing self-consumption with more storage often reduces profitability due to high battery costs. These findings suggest that current policies promoting self-consumption may not align with economic efficiency. Load profile has a limited influence: switching from residential to office or hotel alters yearly savings by no more than ±2 percentage points. However, the residential profile systematically yields lower savings and shows higher sensitivity to cost and pricing assumptions. Sensitivity analysis confirms that savings are highly influenced by implementation costs and electricity price structure. A ± 25 % variation in the price adjustment factor can shift savings by up to 100 %, while changes in battery efficiency affect savings by less than 3 %. These results highlight the need to revise electricity price structures to support economically sustainable self-supply.
Migliari et al. (Thu,) studied this question.