Power storage system

A electric power storage system comprising:

• a solar battery;
• a solar-battery DC/AC converter converting DC power generated by the solar battery into AC power at a prescribed frequency and supplying the converted AC power to AC wiring connected with a load;
• a battery;
• a charger charging the battery using one of DC power and DC power obtained by rectifying AC power supplied through the AC wiring;
• and
• a storage-battery DC/AC converter converting the DC power charged in the battery into AC power and supplying the converted AC power to the AC wiring;
• the solar-battery DC/AC converter working under maximum power point tracking (MPPT) control such that power generated by the solar battery approaches a maximum output, and
• the storage-battery DC/AC converter working such that power supplied to the load through the AC wiring does not fall below a preset value or being controlled such that an amount of conversion into AC power of the storage-battery does not fall below a preset value.