Computers & Laptops

UPS Charging Cost Calculator

What recharging a UPS battery costs after an outage, and over a month of them.

10 inputs Free, no sign-up

Your figures

If you know it in watt-hours. Otherwise fill in the capacity and voltage below.

In ampere-hours, from the label on the battery, together with the voltage below.

Required if you gave a capacity rather than an energy.

Leave blank for this page's 85% assumption. Charging a lead-acid battery is noticeably lossy, and the losses appear as heat and as gassing.

A full recharge from empty. If your outages only take a third of the battery, enter 0.33 rather than 1.

Use fewer for something you only run at weekends.

Rupees per unit (kWh), from your own bill. Tariffs differ by state, by connection and by how much you use, so this is the figure the result is most sensitive to.

Try an example

Result

Your result

Enter your figures and the result appears here.

Estimates only. Rates, fees and specifications change. Confirm against the official source before you rely on a figure — see our disclaimer.

About this calculator

Recharging a UPS battery costs almost nothing, and it is worth being able to say so with a number. A 108 Wh desktop battery recharged from empty pulls about 127 Wh through the socket — roughly a rupee at ordinary Indian tariffs.

How to use this calculator

  1. Enter the battery's energy in watt-hours, or its capacity in ampere-hours together with the voltage.
  2. Say how many full recharges a day and how many days a month. A partial recharge is a fraction — a third of the battery is 0.33.
  3. Enter your electricity rate.

The formula

Energy stored     = Voltage x Capacity
Energy from socket = Energy stored / Charging efficiency
Cost per recharge  = Energy from socket / 1000 x Rate
SymbolMeaningUnit
Capacity Battery capacity Ah
Voltage Battery voltage V
Efficiency Share reaching the battery %

Worked example

A 12 V 9 Ah battery at 85% efficiency, one full recharge a day at ₹8 a unit:

Stored      = 12 x 9        = 108 Wh
From socket = 108 / 0.85     = 127.06 Wh
Per charge  = 0.12706 x 8     = 1.02

About thirty rupees a month, if the power fails every single day.

Notes and limits

  • This is not the whole of what a UPS costs to own. A unit that is switched on draws a standing amount continuously - typically a few watts for the electronics and the float charge - and over a year that is usually far more than the recharging.
  • It is also not a reading from your meter. It is the charging energy at the rate you entered, and nothing more.
  • Lead-acid charging is lossier than lithium, and the losses rise as the battery ages.
  • To cost the standing draw, measure the UPS with a plug-in meter while it is idle and use the electricity cost calculator on that figure.

What this calculation assumes

  • Charging efficiency defaults to 85% and the result names it as an assumption.
  • Only the recharging is counted. The UPS's standing draw when idle is not included.
  • This is energy cost at the rate you entered, not a meter reading.

Frequently asked questions

How much does it cost to recharge a UPS?

Very little. A 108 Wh desktop battery costs around a rupee to refill at ₹8 a unit once charging losses are counted.

Is this what the UPS adds to my bill?

No - it is the recharging only. A UPS that is switched on draws a few watts continuously for its electronics and float charge, and over a year that standing draw is usually the larger figure.

What efficiency should I use for a lead-acid battery?

Charging a lead-acid battery is meaningfully lossy - the 85% default here is a reasonable starting point, and an older battery is worse. The result names whichever figure it used.

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