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Kohler-ups
kohler-ups.ie › home › knowledge base › ups kva load calculator
Kohler kVA Calculator for UPS | kVA into kW Load
September 15, 2025 - Because not all electrical loads use power efficiently—especially when motors, transformers, or other inductive components are involved. That’s where the power factor (PF) comes in. Here’s the simple formula: kW = kVA × Power Factor (PF)
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Fujielectric
india.fujielectric.com › resources › technical-guide › ups-sizing-calculation
Fuji Electric | UPS Sizing Calculation
Arrive UPS output power rating in watts = UPS output in volts-amperes × power factor = 500 X 0.8 KW = 400KW ... Arrive at the adjusted battery power required by taking into consideration design margin, ageing factor and TCF (Temperature correction factor) Adjusted nominal battery load in W/Battery ...
Discussions

How to calculate the kVA requirement for an uninterrupted power supply aimed to last 24 hours?
Get a generator. A UPS needed to power all that would cost a fortune. More on reddit.com
🌐 r/AskElectronics
22
2
January 1, 2015
Calculate UPS size
UPS capacity for how many VA/watts it can handle and how long it will run are completely unrelated. A lot of UPS models in the same line will all use exactly the same battery packs. A typical setup is 2 to 4 7Ah sealed lead acid 12v batteries. If you have a 2-cell battery pack, that's 2*12v*8A == ~170 Watt/hours. Assuming the inverter is 90% efficient, and your 380 watts of power need, expect about a 20 minute runtime. More on reddit.com
🌐 r/homelab
14
15
October 21, 2023
How do I determine UPS runtime? Most UPS specification pages don't list battery capacity (Ah) in the specs
The general guidance is not to have your UPS run as long as possible. Your UPS should do one of two things. One option is to run your systems long enough to shut down. The other is to run them long enough for the generators to kick in. Expectations outside these two use cases are very expensive with diminishing returns. More on reddit.com
🌐 r/homelab
33
25
August 1, 2022
How to calculate runtime on a UPS
It all comes down to energy. Energy is stored in batteries, and used up by devices doing work. The way that energy is transferred is by pushing electrons. Current, measured in amps, is how many electrons are flowing through in a given time. Voltage, measured in volts, is how hard the electrons are being pushed. Power, measured in watts, is the amount of energy transferred in a given time. kilowatt-hours (kWh) is a measure of energy, in more convenient units. So to calculate runtime, you start by measuring the power input into all of your devices. You can get that a couple of different ways. measure the number of kWh used over a time period, and then divide by the number of hours in the time period to get kilowatts. measure the current and multiply by the voltage (power = voltage * current) Once you've got that, you know how fast the energy is draining out of the battery. Now you need to know how much energy is in the battery. According to the specs of the UPS you posted, it has "Battery Volt-Amp-Hour Capacity 845". A volt-amp is the same as a watt (sort of, the difference exsts but isn't important here) so that means the battery has a capacity of 0.845 kilowatt-hours. If the load was 0.845 kilowatts, the battery would last exactly one hour from full charge. If the load is 2.535 kilowatts, the battery will last 20 minutes from full charge. Your power draw in that screenshot is 207.5 volts at 8.6 amps, which is 1.7845 kilowatts. So your battery runtime will be 0.47 hours, or about 28 minutes. There are two caveats for this! The first is that the calculation gives you the theoretical maximum runtime. In reality, it will be less - batteries don't like discharging to zero, and there's always losses in the system. The second is that the calculation is crucially based on that current figure, which will vary from second to second. Device power consumption is never constant, it varies with different computing loads, environmental conditions, which devices are in use and other factors. The most accurate way to get runtime is to measure your total energy consumption over a long period, and then divide by that time period to get an average power consumption. I suspect that the 19 minute runtime remaining is because the UPS is averaging the measured power consumption and that figure is higher than the consumption at the time the screenshot was taken. For your new site calculations, is the site up and running already or do you have to calculate consumption theoretically? More on reddit.com
🌐 r/sysadmin
8
0
April 19, 2024
People also ask

How long will a 10 kVA UPS last?
kVA does not set minutes—battery Wh and kW load do. Small internal packs may yield only a few minutes at full load; extended cabinets run much longer.
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calcpanel.com
calcpanel.com › tools › ups-runtime
UPS Runtime Calculator — Estimate Battery Backup Time at Your Load
What if apparent load exceeds UPS kVA?
Treat overload warnings seriously—reduce kW, improve power factor, or resize the UPS frame in the capacity calculator before trusting runtime minutes.
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calcpanel.com
calcpanel.com › tools › ups-runtime
UPS Runtime Calculator — Estimate Battery Backup Time at Your Load
How to increase UPS runtime?
Add parallel Ah, reduce kW load, improve batteries, or justify a higher safety factor only with engineering evidence.
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calcpanel.com
calcpanel.com › tools › ups-runtime
UPS Runtime Calculator — Estimate Battery Backup Time at Your Load
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Rehlko
ups.rehlko.co.uk › home › knowledge base › kva ups load calculator
Kohler kVA Load Calculator for UPS | kVA into kW
February 11, 2026 - Because not all electrical loads use power efficiently—especially when motors, transformers, or other inductive components are involved. That’s where the power factor (PF) comes in. Here’s the simple formula: kW = kVA × Power Factor (PF)
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Calculatorsconversion
calculatorsconversion.com › inicio › power supply systems and ups › ups capacity in kva and kw calculator – iec, ieee
UPS Capacity Calculator in kVA & kW – Accurate IEC & IEEE
August 19, 2025 - UPS Size (kVA): UPS Size = (10 / 0.85) × 1.25 ≈ 14.7 kVA A 15 kVA UPS is recommended. ... Battery Capacity (Ah): Battery Capacity = 5000 / (192 × 0.9) ≈ 28.9 Ah Selecting 2 × 12V, 100Ah batteries in series (to form 192V) is appropriate.
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Server Room Environments
serverroomenvironments.co.uk › ups-sizing-calculations
How To Size UPS Systems | Server Room Environments
May 8, 2022 - Amps is the current drawn by the load and should be measured at start-up and whilst running. ... For larger VA numbers the VA may be expressed as kVA by dividing the calculated sum by 1000.
Address   St. Andrews Business Centre, Bromfield Industrial Estate, Queen's Lane, CH7 1XB, Mold
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Prostar New Energy
prostarsolar.net › article › how-to-calculate-the-required-ups-load-capacity.html
How to calculate the required ups load capacity?
January 2, 2025 - Reactance reduces the useable power ... power factor (PF). Therefore, the actual power formula for AC circuits is watts = volts x amps x power factor....
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CalcPanel
calcpanel.com › tools › ups-runtime
UPS Runtime Calculator — Estimate Battery Backup Time at Your Load
Minutes ≈ (V × Ah × strings × efficiency × safety × 60) ÷ load (W). Derating, temperature, and OEM discharge curves can change real minutes—see formula notes and worked examples below in the depth section.
Find elsewhere
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Power Saver
power-saver.co.uk › home › what size ups system (kva) means
What Size UPS System (kVA) Means - Power Saver
February 26, 2024 - The formula for AC power is “watts = volts x amps,” which may lead one to believe that a 1,000VA UPS can handle 1,000 watts. However, UPS systems have inefficiencies, and some power is lost in the transformers and circuitry, known as reactance. As a result, most UPS manufacturers specify ...
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Unified Power
unifiedpowerusa.com › home › ups › how to calculate ups load and runtime
How to Calculate UPS Load and Runtime | Unified Power
March 14, 2025 - The power factor of an AC power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit and is calculated as: watts = volts x amps x power factor.
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FS Community
community.fs.com › article › how-to-figure-out-the-required-ups-capacity.html
How to Figure Out the Required UPS Capacity?
For example, large UPS systems are designed based on a power factor of 0.8, which means that a 100 kVA UPS can only support 80 kW of real power. ... The load is the combined amount of power that electrical devices will consume. To calculate the load, one should make an equipment list, which includes the total watts each piece of equipment requires to run properly.
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Server Room Environments
serverroomenvironments.co.uk › ups-sizing
UPS Sizing Guide and Calculations | Server Room Environments
This measurement refers to the Apparent Power drawn by a load and is calculated as follows: Apparent Power (VA) = Supply Voltage (V) x Amps (A) In the formula (V) is the Root Mean Square (RMS) of the supply voltage and the Amps is the current ...
Address   St. Andrews Business Centre, Bromfield Industrial Estate, Queen's Lane, CH7 1XB, Mold
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Powercontrol
powercontrol.co.uk › resources › kva-calculator
UPS Power Calculator
Calculate your UPS power capacity requirements with our UPS power calculator tool. Input details of your load and match with suitably sized UPS systems.
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UST
ustpower.com › home › calculating kva sizes
Calculating kVA Sizes - UST
August 10, 2022 - Multiply the voltage by the current and divide by 1,000 to obtain the size rating in kVA ... AC amperage is a measure of the flow of current to a device or in a circuit. Electrical devices draw varying amounts of current depending upon their operating state or the amount of work they are doing.
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Omni Calculator
omnicalculator.com › physics › kva
kVA Calculator
March 22, 2024 - Kilovolt-amps, abbreviated as kVA, is the typical unit of measure for what is called apparent power. Apparent power is the amount of electrical power produced by an electrical system at a particular applied voltage and current. Following the Ohm's law formula, we can obtain the amount of electrical power by multiplying the amount of voltage by the current flow through any electrical system.
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Eaton
upsselector.eaton.com › Load
UPS Load Calculator, How Much Power Will Your UPS Use? - Eaton
How Much Power Will Your UPS Use? Choose the right UPS, uninterruptible power supply, based on your total power consumption, Eaton UPS Selector
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Reddit
reddit.com › r/askelectronics › how to calculate the kva requirement for an uninterrupted power supply aimed to last 24 hours?
r/AskElectronics on Reddit: How to calculate the kVA requirement for an uninterrupted power supply aimed to last 24 hours?
January 1, 2015 -

Hi everyone,

I'm frequently back home in India where power outages can become rather bothersome.

I'm basically trying to calculate the kVA requirement for my home using the power calculator here: http://www.su-kam.com/load-chart.aspx

Although I can roughly understand the concept of the load being put on the system, I cannot figure out how long the backup power will last.

Power failures in my city can be as long as a whole day (not 8 hours, but the whole 24 hour shabang). So, I am trying to calculate the kVA needs for:

  • 1 x 48 inch plasma screen (in reality we have a 55" LED TV)

  • 1 x 1000W music system

  • 1 x 480L fridges (this is the critical component in the house that absolutely needs to be powered)

  • 20 x 22 watt CFL lights

  • 1 small printer

  • 1 small scanner

This usually results in 10,000VA - 15,000VA on the website, but what it doesn't say is how long we can keep these items powered on for.

Now, I know most of the time all these equipment will be turned off (except the fridges: food spoils REAL fast in hot and humid places), but it would be nice to know that we can power all this for 24 hours (if need be).

So the base question is, how do I calculate the kVA requirement for all the above items if I want to power them for 24 hours?

Thanks!

EDIT: Based on advice below, I am shifting to only needing to power a single 480L fridge + a ceiling fan + a few CFL lights. I've put my calculation below for people to check whether I am correct in my approach.

EDIT2: Number of fridges now goes to only one.

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Server Room Environments
serverroomenvironments.co.uk › blog › how-to-size-ups-systems-in-kva-and-kw
How To Size UPS Systems In kVA and kW | Server Room Environments
May 16, 2021 - VA measures the ‘Apparent Power’ being drawn with the formula being: load amperage (Amps) drawn multiplied by the mains power supply voltage (V). To work out the kVA the VA is multiplied by 1000.
Address   St. Andrews Business Centre, Bromfield Industrial Estate, Queen's Lane, CH7 1XB, Mold
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Riello UPS
riello-ups.com › questions › 32-how-do-i-size-a-ups-correctly
How Do I Size A UPS Correctly?
The power consumption of electrical equipment is stated in either Watts (W) or Volt-Amperes (VA). Because UPS systems are rated by VA or kVA ratings, this may require a conversion from W to VA, which can be calculated by dividing the power consumption (W) by the power factor.