5 Things You Need to Know About Battery Energy Storage Systems (BESS)
Battery Energy Storage Systems (BESS) are transforming how temporary power is delivered across construction, utilities, industrial sites and events. But there are still many misconceptions about what these systems do and how to use them effectively.
Here are the five things you really need to know if you're considering integrating a BESS into your power setup.
Batteries aren’t magic — they’re stored energy used intelligently
A BESS doesn’t generate free electricity. It stores energy that must first come from another source such as a generator, a grid supply or renewables like solar and wind. Once charged, the value of a BESS is in how efficiently and intelligently it releases that stored energy. It delivers power instantly when loads fluctuate, helping stabilise your supply and support your generator or grid connection when demand suddenly increases.
A BESS allows you to use smaller generators without compromising performance
One of the biggest advantages of integrating a BESS is power assist. Rather than running a large generator to handle occasional spikes in demand, you can run a smaller, more efficient generator (or grid supply) and allow the BESS to support it.
For example:
If you have an 80 kW supply feeding into the battery and your site momentarily needs 100 kW, the battery will automatically deliver the additional 20 kW. This means:
- No generator overload
- No need to oversize your equipment
- Lower fuel consumption and emissions
Smaller generators paired with a BESS can comfortably support larger, more fluctuating loads.
BESS units handle high-impact loads that generators alone can struggle with
Generators don’t always cope well with sudden, heavy load steps. Large spikes can cause frequency dips, voltage instability or even full trips, especially when equipment starts abruptly or demand rises faster than a generator can respond. A BESS, however, can react instantly. Its inverter absorbs rapid swings in demand without any noticeable drop in voltage or frequency, maintaining a stable and resilient supply even when loads are unpredictable.
This kind of stability is especially important on projects where sensitive equipment is in use or where uninterrupted power is critical. A recent example is our temporary power solution for a school affected by RAAC, where pupils were moved into modular classrooms. These classrooms relied on a variety of electrical systems that do not always ramp up gently — lighting banks, heating controls, and other classroom infrastructure that can create sudden demand spikes throughout the day. By integrating a BESS into the temporary power setup, we ensured that every load step was handled smoothly, without placing strain on the generator or risking outages that could disrupt learning time.
The BESS supported the generator by instantly smoothing out those sharp increases in demand, keeping the power supply stable and preventing any fluctuation or generator stress. This not only protected the equipment but also created a quieter, lower-emission environment for the school — something especially important to avoid disruption to lessons and to the surrounding neighbourhood.
For sites with motors, pumps, cranes, compressors, modular buildings or any equipment that doesn’t come online gradually, this fast-response capability is one of the major advantages of deploying a BESS. It ensures performance remains consistent, even under challenging or unpredictable loads.
BESS are incredibly effective for peak shaving and reducing runtime
Peak shaving is one of the most effective uses of a BESS. Rather than running a generator sized for the absolute maximum demand, you run a smaller, more efficient unit and let the BESS cover the higher loads whenever they occur. The battery recharges during quieter periods, and if it ever approaches its limit, it can call for a fixed-load support generator to run briefly at a controlled output. Once the battery has recovered, the support generator automatically stops. This approach significantly cuts fuel use, emissions and runtime.
This same principle can also solve grid-capacity problems. A real-world example involves a chain of restaurants we supported. Each location only had a 100 A three-phase grid supply, but during busy periods their demand could spike to 150–200 A. Upgrading the grid connection would have been expensive and slow, so instead we installed a BESS to shave the peaks. The battery drew a consistent, safe amount of power from the grid and seamlessly delivered the extra amperage during peak times. Overnight, when demand dropped, the BESS recharged. This allowed the restaurants to operate normally without any costly infrastructure upgrades or power restrictions.
A BESS adds resilience and can function like a UPS
With the right configuration, a BESS can maintain a set state of charge — for example, 80–85% — so it’s always ready to take over instantly if the grid supply fails or a generator stops unexpectedly. It can support the full site load while a standby generator starts or until the grid returns, providing a smooth and uninterrupted transition. This makes it a powerful tool for sites where downtime isn’t an option and where power reliability is critical.
Why BES matters for Modern Power Solutions
BESS technology is no longer a “nice to have” - it’s a smarter, cleaner and more resilient way to manage temporary power. It allows you to optimise generator sizing, reduce fuel consumption, manage sudden loads, stabilise your supply and integrate renewables more effectively. For many of our customers, a BESS is now a core part of their power strategy.