A UPS includes a first transfer switch, a first battery charger, a second transfer switch, a solar energy absorption board, and a second battery charger. The first transfer switch connects a power source to an electrical device. The first battery charger connects the power source to a storage battery for charging the storage battery. An output of the storage battery is connected to the first transfer switch via an inverter. The first transfer switch controls the storage battery to supply power to the electrical device. The second transfer switch is connected between the first battery charger and the storage battery. The second battery charger connects the solar energy absorption board to the second transfer switch. The second transfer switch controls the power source to charge the storage battery via the first battery charger or the solar energy absorption board to charge the storage battery via the second battery charger.