Energy and Smart Building Industry Blog

Making Sense of the Leading Energy Storage System Technologies


Backup power is essential for reducing downtime and ensuring continuous operations of your buildings and equipment. Understanding the differences between commercially available power storage options can help you save your organization time, energy, and money. In this post, we look at the top uninterrupted power sources (UPS) battery backup systems on the market and outline their capabilities and costs.

Why is Battery Backup Important?

According to a 2021 report, the average cost of just a single hour of downtime has risen to $84,650. However, the true cost can be much higher when factoring in other influences, which include:

  • Loss of customer and employee confidence
  • Damage to brand integrity
  • Diversion of resources from long-term business-critical projects
  • Reduced stock prices
  • The threat of legal action
  • Revocation of licenses or accreditations

The market for uninterrupted power supplies is growing rapidly due to the wealth of organizations whose success depends on the ability to keep systems, networks, and platforms running at all times without unexpected downtime. 

Top UPS Energy Storage Systems

There are four leading types of uninterrupted power sources, or UPS, that give your buildings the ability to maintain operations in the event of a critical power failure. They each provide different technical capabilities and advantages depending on the building control systems you are already using and what your current UPS situation looks like. 

The four leading UPS technologies are:

  • Lead-Acid Batteries 
  • Lithium-Ion Batteries 
  • Nickel-Zinc Batteries 
  • Flywheels/Rotary Systems/Crankshafts 

Energy Terms

To better understand the unique benefits and challenges of deploying one solution over another, you need to be familiar with the following terms:

  • Cycle Life: The measurement of the number of times a battery can be reduced in power to 50% or less and then adequately charged back to 100% capacity. 
  • Discharge Rate: This measurement of time it takes for an energy storage system to completely discharge or deplete all of its energy reserves. 
  • Thermal Runaway: This describes what happens when an energy storage system cannot safely and adequately discharge its generated heat. (Excessive thermal runaway can lead to hazardous explosions.) 
  • Battery Management System: A platform or system used by facilities managers to evaluate the performance of energy storage systems in real-time. 


Comparing UPS Technologies 

Lead-Acid Batteries 

Lead-acid batteries remain the most tried and trusted energy storage system deployed to provide backup power. For facilities already using lead-acid batteries, there is likely little incentive to switch over to a new system that would require firmware or platform updates to work correctly. 



Lead-Acid Battery Capabilities

Lead-acid batteries are likely to support between 300 and 600 discharges and typically have a warranty of 3-5 years. However, it is not uncommon for facilities managers to replace them several times over the 10-year life span of their UPS system. 

Lead-acid batteries support high power discharges and are suited for high-current applications. The best lead-acid batteries for UPS systems can handle a 7.5 (8C) to 10 minutes (6C) discharge rate. They can recharge in as little as two or as many as 24 hours, depending on various factors. 

Lead is a very dense and heavy metal. As a result, lead-acid batteries take up a great deal of space and require extensive cooling support to run correctly. Temperatures above 76 F (25 C) are likely to degrade or damage lead-acid batteries.

Furthermore, lead-acid batteries require quarterly maintenance every 3 months to continue running optimally compared to other leading energy storage devices. Though their initial cost is much lower than other energy storage systems, the cost of constantly replacing and maintaining lead-acid batteries will add up over the years. 



Lithium-ion (Li-ion) batteries are a much newer innovation in the area of UPS technology. One of the main advantages of this energy storage system is that Lithium iron phosphate batteries deliver a  cycle life of 1,000 to 3,000 discharges and can last for 10-15 years. 



Lithium-Ion Battery Capabilities 

Lithium iron phosphate batteries typically can supply 2-minute (30C) discharge rates, which is a major advantage for UPS applications. Additionally, these batteries are likely to be completely recharged in around 2 hours after depletion. 

Lithium-ion batteries weigh 60-80% less than lead and only require about 50% of the floor space. They can also safely and efficiently operate at 86 F (30 C), which helps to reduce additional cooling costs. 

Li-ion energy storage systems do not need to be tested quarterly like lead batteries but require a yearly inspection. These batteries are likely to cost 1.2 to 1.5 times as much as their lead-acid competitors. 

Additionally, because lithium iron phosphate has a thermal runaway temperature of 518 F (270 C), a pierced battery could result in a severe explosion or fire. 


Nickel-Zinc Batteries 

Nickel-Zinc batteries are quickly emerging as one of the more innovative energy storage systems available for UPS applications. High-quality nickel-zinc batteries deliver an average cycle life between 600 cycles at 100 percent depth of discharge and up to 150,000 cycles at 1 percent depth of discharge. 



Nickel-Zinc Battery Capabilities

These batteries support a maximum discharge rate of 6 minutes (12C) and can be charged from 0 to 93% or higher in less than an hour, though many can take up to 4 hours to reach a complete 100% recharge. 

Nickel-zinc batteries are about half the size of comparable lead batteries. They are likely to take up a much smaller footprint. One of the main advantages of nickel-zinc batteries is their ability to operate at even extremely high temperatures without being damaged or degraded, which leads to significant cost savings over the life cycle of your facility. 

Compared to leading lead battery solutions, nickel-zinc does not require quarterly testing, though a yearly inspection is recommended. 

Although the initial cost of nickel-zinc batteries is higher than lead batteries, their lifetime value is typically higher. Additionally, these batteries pose no fire risk and do not have any thermal runaway potential. 

Flywheel Batteries

A flywheel system uses the power of kinetic energy or movement to generate and disperse power. As a result, flywheels do not have a cycle life. Their storage capacity does not diminish at all with repeated use over many years. 


flywheel batteries


Flywheel Battery Capabilities

Flywheels can typically discharge their power in 15 to 20 seconds and can recharge in just 2 minutes. Magnetic flywheels are the most powerful and efficient when discharging the highest amount of energy as quickly as possible. 

Flywheels are relatively small in size relative to their power output. Their size footprint is closest to lithium-ion batteries, and they are considerably lighter than lead-acid energy storage systems. Additionally, flywheel systems do not have the same intensive cooling needs as many batteries. 

Traditional flywheel systems run using mechanical ball bearings typically require regular maintenance. Newer models using magnetic power do not require the same amount of maintenance or replacement parts. 

Flywheels and lead-acid batteries are likely to have similar initial costs. However, due to savings from reduced cooling and maintenance needs, flywheels could be less expensive over their complete life cycle. 


Bringing Down Energy Costs

If you are looking to bring down energy costs and usage across your facilities, we encourage you to check out our guide Adaptive Energy Management - How to Use Your Buildings as a Battery

Adaptive energy management uses building monitoring systems, automation, and A.I. to help you reduce usage and save on energy spend across your portfolio. The guide outlines how you can:

  • Even out energy demand curves
  • Cut down on energy demand during peak hours to reduce peak charges
  • Keep occupants cool even on hot days
  • And much more! 

Download the free guide to learn more!

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Additional Resources:

Top 3 Benefits of Benchmarking for Facilities Management
Energy Efficiency AND Customer Comfort CAN Coexist
Smart Buildings, Building Automation - What's the Point?

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