A UPS on the other hand, is a simple solution which offers electrical backup power for limited duration, but does not offer any saving. The duration of the backup electricity supply depends on the size of the battery and the load placed on the battery. An inverter is used to convert the energy stored in the battery (Direct Current) to usable alternating current in your house. The battery is charged while the electrical utility grid is available, through the inverter/charger. This stored energy in the battery is then available for the inverter to automatically convert and start powering connected loads (lights, TV fridge etc).
The size of the inverter determines what appliances can be powered simultaneously, and the capacity of the battery defines how long the connected loads (lights, TV fridge etc) will be able to operate before the battery need to be charged again.
A UPS does not introduce or offer any saving, but is only a solution to keep the lights on, when the grid utility supply is off.