Peak Demand Charges Explained: Reducing Costs During High Usage
If your business electricity bill has a line you don't recognise, it might be a peak demand charge. It's one of the least understood costs on a commercial bill, and one of the easiest to bring down once you know what's driving it.
What are peak demand charges?
Peak demand charges are based on the highest amount of power your business draws during a set period, not the total energy you use over the month. They're measured in kW or kVA, separately from the kWh figure that covers your day-to-day consumption.
In practice, this means two businesses with the same monthly usage could pay very different amounts. A business with one big spike in demand, several machines starting up at once, will often pay more than a business using the same total energy spread evenly across the day.
How they're calculated
Peak demand charges sit within the network costs on your bill, known as DUoS (Distribution Use of System) and TNUoS (Transmission Use of System). These cover the cost of moving electricity from the National Grid to your premises, and they're set by Ofgem, not your supplier.
Ofgem's Targeted Charging Review reformed how these charges work. Before the review, larger sites could reduce their transmission costs by avoiding the three half-hourly "Triad" periods of peak winter demand, a practice the National Energy System Operator confirms Ofgem viewed as shifting costs unfairly onto customers who couldn't do the same. Since the reforms took effect, more of the cost sits in fixed daily charges instead, so similar-sized businesses pay similar amounts regardless of when they draw power.
If you're on a half-hourly meter, standard for larger sites and governed by Elexon's Balancing and Settlement Code, your demand is recorded automatically in 30-minute intervals. Exceeding your agreed capacity with your network operator can trigger an additional charge on top.
Why this matters more from September
As shorter days and cooler weather set in, business energy demand starts climbing again, and so does the value of understanding what's driving your bill before winter usage picks up further. Getting ahead of it now, while it's a planning exercise rather than a live problem, tends to save more than reacting to it in January.
Who peak demand charges affect most
-
Businesses on half-hourly meters, usually those using more than 100,000 kWh a year, where demand is recorded automatically under Elexon's settlement rules
-
Manufacturing, warehousing and other operations where several pieces of equipment start up at the same time
-
Businesses that have grown or changed their equipment since their capacity was last agreed, and may now be exceeding it
If you're not sure whether you're on a half-hourly meter, that's worth checking first. It determines how much of this actually applies to you.
How to reduce peak demand charges
- Check your agreed capacity. If it's set higher than your business actually needs, you could be paying for headroom you never use.
- Look at when your usage spikes. Staggering equipment start-up times, rather than switching everything on at once, can lower your recorded peak.
- Consider on-site generation or storage. Solar generation or battery storage can reduce how much you pull from the grid at your busiest moments, which is what your peak demand charge is based on.
- Ask your supplier for your half-hourly data. It shows you exactly when your demand is highest, so you're working from evidence rather than guesswork.
- Review before you renew. Peak demand patterns change as a business grows or its equipment changes, so it's worth rechecking at each renewal rather than assuming last year's setup still fits.
Get help managing your peak demand costs
Reading your own peak demand exposure from a bill isn't always straightforward, and the right fix depends on your usage pattern and agreed capacity. If you'd rather have someone else do the reading, compare business electricity deals with us, or speak to an advisor about your market data and what it means for your bill.
Peak demand charges: FAQs
-
Is peak demand the same as my total energy usage?
No. Total usage (kWh) is how much energy you use over time. Peak demand (kW) is how much power you draw at your busiest moment. You can have low overall usage and still pay a high peak demand charge if that usage happens in short, sharp bursts.
-
Do all businesses pay peak demand charges?
Not directly. They mainly apply to larger sites on half-hourly meters, as set out under Elexon's settlement rules. Smaller businesses on standard meters are less likely to see this as a separate line, though the same network costs are still built into their unit rate.
-
What happens if I exceed my agreed capacity?
Your network operator can charge you extra for going over the demand level you agreed. It's worth checking that your agreed capacity still matches how your business actually operates, particularly after growth or new equipment.
-
Can switching supplier reduce peak demand charges?
Not on its own, since these are network costs set by Ofgem and your regional distribution network operator, not by your supplier. What switching can affect is the unit rate and standing charge sitting alongside them, which is where comparing deals still makes a real difference.