The cost of electricity is measured in kilowatt-hours (kWh). That's the number most manufacturers focus on, but it isn't the only figure driving operating costs, and for many sites, it isn't even the biggest one. Peak demand charges are often overlooked, despite having a significant impact on electricity bills. A single short period of high demand can increase costs for a whole billing period, regardless of how efficiently the site runs for the rest of the month. Margins can be reduced before the first product has even left the production line.
What are peak demand charges?
Unlike standard energy charges, which are based on total electricity consumed, peak demand charges are based on the highest level of power your site draws from the grid at any one time, your peak demand, typically measured in kilowatts (kW).
Your electricity supplier or Distribution Network Operator (DNO), depending on your tariff, uses this peak to assess the strain your site places on the local network. The higher the peak, the higher the charge.
This shows up on your bill in a few different forms, and they’re easy to miss buried in a commercial invoice:
- DUoS (Distribution Use of System) charges — banded by time of day into Red, Amber and Green periods. Red bands (typically weekday early evenings, when the national grid is under most pressure) carry a much higher rate per kW than Green. A manufacturing site running a late shift can walk straight into Red-band pricing without realising it.
- Capacity charges — some tariffs charge for the maximum capacity you’ve contracted with your DNO, whether or not you use it, and penalise you further for exceeding it.
- Triad charges (for larger sites on transmission-connected or half-hourly settled supplies) — based on the three half-hour periods of highest demand on the national grid each winter. Miss-timing production around a Triad window can add a disproportionate cost to the year’s transmission charges.
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Manufacturing sites are particularly exposed to all of this because electrical loads fluctuate by nature. Production equipment, process heating, compressed air, refrigeration, extraction, and material handling can all switch on within minutes of each other, starting several machines at once, running compressors alongside HVAC, or bringing production online at the start of a shift. Even highly efficient factories can see sharp demand spikes simply because of how operations are scheduled.
Many businesses focus on reducing total consumption but pay less attention to when that energy is used. The result: demand charges erode profitability month after month, often invisible until someone reviews the half-hourly data underneath the bill.
The cost of short demand spikes
Take a manufacturing facility that normally operates at around 250 kW. At 8:00am, production lines, compressors and ventilation start together, pushing demand to 450 kW for just 15 minutes. The factory quickly returns to its normal operating level — but that 15-minute spike, not the other 43,185 minutes in the month, can set the site’s maximum demand for the entire billing period, and depending on the tariff, potentially the Triad exposure for the following year too.
How Battery Energy Storage Systems reduce peak demand charges
Battery Energy Storage Systems (BESS) work by supplying electricity during peak demand periods rather than drawing more power from the grid. Instead of letting site demand spike, the battery discharges stored electricity to support the load. This process, peak shaving, smooths the site’s demand profile and reduces the maximum power imported from the network.
From the grid’s perspective, your site becomes more predictable and places less strain on local infrastructure. For the business, that can mean lower demand charges without disrupting production, and it can also mean avoiding a costly DNO grid reinforcement bill that would otherwise be triggered by rising peak demand as production scales up.
Sizing matters here. A battery’s power rating (kW) determines how much of a spike it can cover; its energy capacity (kWh) determines how long it can sustain that output. A system sized only for a brief morning start-up spike looks very different from one designed to also shift load out of a Red DUoS band for several hours, getting this right is a site-specific engineering exercise, not a standard package.
Where solar is already on site, or being installed alongside the battery, the two work together. Surplus generation is captured and held for use later in the day, once demand is still running but solar output has dropped. This raises the self-consumption rate of the solar installation, the single most important variable in determining long-term solar ROI. For sites with existing solar, adding storage can unlock value that’s been quietly slipping away since commissioning.
More than just lower electricity bills
Reducing demand charges is often only one part of the commercial case for battery storage. A well-designed BESS can also help manufacturers:
- Store lower-cost electricity for use during expensive periods, including Red-band DUoS windows
- Maximise the value of any on-site solar generation
- Keep processes running during grid outages or voltage drops
- Create headroom for growth without triggering a DNO capacity upgrade
- Support future electrification of heating, transport or process equipment
- Participate in grid flexibility schemes (such as Demand Flexibility Service events), turning a cost-avoidance asset into a revenue opportunity in its own right
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As manufacturing processes become increasingly electrified, heat pumps replacing gas process heating, EV fleets charging on site, controlling demand is becoming just as important as reducing consumption. A site that doesn’t manage its demand profile now is likely to find electrification amplifies the problem later.
Is your site paying more than it needs to?
Many manufacturers are unaware of how much demand charges contribute to their overall electricity costs, largely because the half-hourly data that reveals it isn’t something a standard bill surfaces. A renewable energy expert can review that data alongside your load profile and tariff structure, revealing opportunities that aren’t obvious from the monthly total.
In many cases, relatively small changes to how electricity is managed, shifting a start-up sequence by twenty minutes, staggering compressor loads, or adding a modestly sized battery, can deliver meaningful long-term savings without affecting production output.
Battery storage isn’t the right solution for every site, the value depends on your operating profile, tariff, existing infrastructure and future energy plans. That’s why a detailed assessment matters before any investment decision.
If you’d like to understand where peak demand is affecting your business, Green Shield Group can assess your site’s electricity profile and identify whether battery storage could deliver measurable commercial value.
