What Is the Run Time of an Uninterruptible Power Supply (UPS)?

The runtime of a UPS determines how long it can stay on powering your devices before its internal battery runs out. It tells you when you must either shut down your electronics properly or find a more sustainable backup energy solution. 

Not every UPS has the same run time, so it’s critical to understand which factors impact UPS load and run time and what calculations you can use to determine an estimated UPS runtime. 

What Is a UPS?

UPS stands for uninterruptible power supply. This energy solution is a critical backup electricity source that turns on immediately when an outage is detected, maintaining electricity to connected electronics. It’s a safety net that protects sensitive equipment, ensures continuous operation, and allows you the time to shut it down correctly to avoid losing data or damaging the hardware.

These systems work well for unexpected short-term backups but aren’t designed for extended runtimes. Modern solutions like EcoFlow Portable Power Stations or the EcoFlow DELTA Pro + Smart Generator can help, offering extended operation of your essential appliances or electronics even during prolonged blackouts. 

How Does a UPS Work?

UPS systems constantly monitor the incoming electricity supply through the plug they’re connected to. When they notice a disruption in the power, they switch over to using their battery power instantaneously, avoiding any interruption to their connected devices. This can preserve data or progress, allow you to run a full shutdown of the equipment, and protect delicate hardware. 

These backup systems consist of batteries, inverters, and sophisticated electronics that work with the incoming electricity level (whether strong, fluctuating, or unavailable) to ensure a stable output. Electronics are so advanced today that even minor fluctuations in energy can cause damage, so having a UPS has become increasingly important. 

Factors to Consider When Calculating UPS Load and Runtime

All uninterruptible power supplies offer different runtimes based on the system’s rating, total load, and battery capacity.

UPS Rating

UPS ratings are measured in volts amps (VA), kilowatts (kW), or kilo-volt-amperes (kVA), indicating the maximum energy the uninterruptible power supply can deliver. However, the Watts rating determines the UPS’s “real power.”

In a circuit running on direct current (DC) energy, watts equal volts times amps, where 1 kW = 1 kVA. When the uninterruptible power supply uses AC energy, which is what most buildings run on, it reduces the available wattage, creating what’s known as a power factor. The power factor is the ratio of the real power absorbed by the load to the apparent power still flowing within the circuit. 

You can calculate this as watts = volts x amps x power factor. The power factor varies from system to system. A 100 kVA system may have a power factor of .8, meaning it can only actually support 80 kW of real power, not the 100 kVa you may think.

The higher the UPS rating, the more capacity it has to support higher-power equipment or multiple devices at once

Power Load

Your load is the combined power that all connected devices consume. The higher the load, the harder the UPS has to work to keep everything running. To calculate your load, add the total watts of each device or piece of equipment your uninterruptible power supply will protect. This total number is the total wattage your UPS will carry. 

If your uninterruptible power supply can handle your energy load with little margin, you may run into fluctuations or surge issues, so you should build a buffer just in case. The same goes for other energy storage solutions – whether you’re purchasing the EcoFlow Smart Generator (Dual Fuel) or another battery backup, ensure its output exceeds your required wattage.

Battery Capacity

While load encompasses the total power of the equipment the uninterruptible power supply must protect, capacity determines how long it can sustain that load during an outage, otherwise known as runtime. Every UPS internal battery can supply a limited amount of energy, and once it reaches that point, a new source must be connected to prevent a sudden shutdown. 

An alternative to this cutoff time is finding a system that integrates into your home and immediately switches on to a more extensive power source when needed, like the EcoFlow Powerstream Microinverter. Not only does an inverter switch on automatically like a UPS, but it can tap into renewable energy generation, such as solar generators, to continuously power your electronics without a definite runtime.

How to Calculate UPS Load and Run Time

Your manufacturer may offer an uninterruptible power supply runtime calculator tool or formula to make it easy to understand. However, you can also gather specific measurements and follow the steps below to find your UPS load and run time. 

Just note that adding more batteries can increase run time to support the load; it cannot increase the uninterruptible power supply capacity.

Size Calculation:

1. Add up all the amps and volts for each device or piece of equipment you will connect to the UPS.
2. Multiply amps by volts to determine volt-amps (VA). To convert watts to VA, divide the wattage by the power factor.
3. Add up all the VA subtotals to get the total power load requirement.
4. Multiply this by 1.2 to get the grand total, accounting for future expansion.
5. Ensure that the VA requirement of all your supported equipment does not exceed the UPS’ VA rating.

Backup Time Calculation:

1. Multiply the battery rating (Ah) x the battery rating (V) x the number of batteries x battery efficiency
2. Divide this figure by the load in watts.
3. This is your uninterruptible power supply run time. After that, you’ll need another power source for additional backup time.

If your UPS offers 10-15 minutes of runtime and you don’t have a backup generator, you can use this time to safely shut down your equipment, saving any progress or data along the way. If you have a generator, you can use this time to keep your equipment connected until the generator is up and running. 

Frequently Asked Questions

Final Thoughts

UPS are lifesavers, protecting sensitive equipment and allowing you to properly shut down electronics and appliances when a sudden outage strikes. However, their runtimes are often limited to a few minutes and are not intended as long-term backup sources. If you want something that works just as seamlessly with longer backup times, consider investing in EcoFlow Inverter Generators for your home.