Energy self-sufficient households with photovoltaics and electric vehicles are feasible in temperate climate

multiplied by 24 hours. Eq 1 shows the entire approach: CcaseX kWh day � � ¼ ðQsouth þ Qwest þ QeastÞ 3 � kW kWp � � � 1 0:108 ð Þ � LCaseX ½kWp� � 24 h day � � ð2Þ The necessary yield to cover energy demand on each day (DCaseX) is computed by dividing the optimized monthly energy production (YMonthZ), which is required to satisfy the demand in this month, through the amount of days of this particular month (NMonthZ): DCaseX ¼ YMonthZ NMonthZ ð3Þ On days where the difference between DCaseX and CCaseX is negative, the shortfall has to be compensated by energy from the hydrogen system. We assume that if the yearly positive off- sets, with the inclusion of the long-term storage efficiency in the hydrogen system of 38.3%, are high enough to outbalance the negative offsets, it is possible to rely fully on the energy pro- duced in this year. Thus, the following inequality must hold true for a case to be considered Table 3. Cost assumptions for the self-sufficient cases. All costs are in 2019 CHF. Price in 2050 [CHF2019] Source Lifetime [years] Source Solar PV Investment costs [CHF/m2] 200.- [11], [64], own assumptions 25 [11] Investment costs [CHF/kWp] for 22.1% efficiency 905.- - - - Investment costs [CHF/kWp] for 27.2% efficiency 735.- - - - O&M costs [CHF/kWh] 0.02 [11], [65], own assumptions - - Heat pump Investment costs–SFB 36,000.- [66] 20 [11] Investment costs–MFB 136,800.- Own assumptions - - O&M costs 200.- [66] - - Battery Capital costs [CHF/kWh] 265.- [48], [54], [67], own assumptions 15 [53], [54], [61], own assumptions

BOS costs 2000.- [68] - - Additional Hardware costs (part of investment cost) 740.- [54] 15 [53], [54], [61], own assumptions O&M costs 4.5% of investment costs [61] - - Electrolyzer Capital costs [CHF/kW] 70 633 CHF ½ � � X 0:276 kW ½ � � 2 3 [69], [70], own assumptions 22 [11], own assumptions BOS costs 30% of capital costs [61] - - O&M costs 5% of capital costs [61] - - Storage tank Investment costs 600 CHF m3 � � � XCaseX m3 ½ � [71], own assumptions 22 [11] BOS costs 2500 Own assumptions - - O&M costs 3% of investment costs [61] - - Fuel cells Capital costs [CHF/kW] 60 506 CHF ½ � � Y 0:177 kW ½ � � 1 3 [11], [61], own assumptions 22 [11], own assumptions BOS costs 30% of capital costs [61] - - O&M costs 10% of capital costs [61] - - https://doi.org/10.1371/journal.pone.0227368.t003 Energy self-sufficient households with photovoltaics and electric vehicles are feasible in temperate climate PLOS ONE | https://doi.org/10.1371/journal.pone.0227368 March 4, 2020 9 / 25