Achieving carbon neutrality requires wider adoption of renewable energy (RE), electric vehicles (EVs), and reused vehicle batteries. Community microgrids (MGs) can support local energy management by balancing supply and demand and improving the utilisation of variable renewable generation. This paper evaluates the long-term economic performance of a community MG integrating photovoltaic (PV) generation, biogas power generation (BG), reused nickel–metal hydride (Ni-MH) batteries, reused lithium-ion batteries (LIBs), and municipal fleet EVs through a V2X system. Reused Ni-MH batteries are used for PV output smoothing, whereas connected EVs and reused LIBs are used for power balancing.

Three models are compared: a normal charging model, a planned-purchase V2X model, and a zero-purchase V2X model. In the normal charging model, EVs are charged without V2X discharging, and BG output is set on the basis of minimum demand. The planned-purchase V2X model uses a 59.4 kWh reused LIB and coordinates BG output adjustment with planned grid power purchase to mitigate reverse power flow during low weekend demand. BG output is determined from the cumulative deviation of weekend residual demand, while planned power purchase is regulated according to the average state of charge (SOC) of connected storage devices. The zero-purchase V2X model uses a 574 kWh reused LIB, with BG output set on the basis of weekly average net demand to eliminate grid power purchases.

Numerical simulations were conducted for seven days using MATLAB/Simulink R2019b. Identical demand and PV profiles were applied across all models, and the initial and end-of-week SOC conditions were set to prevent significant energy imbalances between consecutive weeks, enabling the weekly results to be annualised. Seasonal variations in demand and PV generation were not considered; therefore, the annual costs represent estimates under the assumed representative-week conditions. The 15-year economic evaluation included initial, operating, and replacement costs and subsidies. The minimum evaluation period required for the lowest-cost model to become more economical than the normal charging model was also investigated.

The planned-purchase V2X model achieved the lowest annual average cost over 15 years at 16.147 million JPY/year, 6.7% lower than the normal charging model. Its annual power purchase cost was reduced by 2.735 million JPY, and the accumulated savings offset the additional V2X and reused-LIB costs. The model became more economical from six years onwards. In contrast, the zero-purchase V2X model eliminated grid power purchase costs but had the highest annual average cost because of the large reused-LIB capacity and increased BG maintenance costs. These results indicate that planned V2X operation with moderate battery capacity provides a better balance between equipment investment and power purchase cost reduction than eliminating grid power purchases.