Your TNUoS charges are made up of two parts. The first, the residual, is a fixed daily charge based on your site's banding. It makes up over 90% of the total for most businesses and can't be reduced by changing how you use electricity. The second, the locational demand element, is smaller and varies depending on your demand during peak periods and where your site is in GB.
In this article, find out how each part is calculated, what determines your band, and what to check on your own site.
How the residual charge is calculated
The residual makes up the bulk of your TNUoS charge, and what you pay depends on your band.
How banding works
Your band determines your daily TNUoS charge. Every commercial site in GB is classified into a band based on two factors:
- Your connection voltage (low, high, extra-high, or transmission)
- Your agreed supply capacity or consumption level, depending on your meter type
NESO (the National Energy System Operator) sets the band boundaries at the start of each five-year price control period. The current boundaries were set in April 2026 and apply through to 2031. But the band your site is in can change within that period if you successfully apply to reduce your agreed supply capacity through your distribution network operator (DNO).
One thing worth knowing is that the same banding structure applies to both TNUoS and DUoS. If your banding changes for one, it's likely to change for the other, which doubles the impact. If you request a capacity review and your TNUoS band drops, ask your DNO whether the same applies to your DUoS. In most cases, the two go together.
Tip: Not sure who your DNO is? Check your electricity bill, as you can normally find it on there. You can also use the Energy Networks Association's postcode lookup at energynetworks.org/customers, or just ask your energy supplier. There are 14 regional DNOs across GB, so which one you deal with depends on where your site is.
What determines your band
Higher voltage and higher agreed capacity put you in a higher band, which means a higher daily charge. The risk is overcapacity. If your agreed capacity is higher than your site actually needs, you could be in a band above where you need to be, paying a higher daily rate as a result.
This happens more often than you'd think. Sites where demand has dropped since the original connection was set up, or sites that were over-specified from the start, end up paying more every day than a comparable site with the right capacity.
For example, take two sites that use similar amounts of electricity:
| Site A | Site B | |
|---|---|---|
| Agreed supply capacity | 200 kVA (the maximum its connection can deliver) | 150 kVA |
| Actual peak demand | 120 kW (the real power the site uses) | 120 kW |
| TNUoS band | Higher | Lower |
| Daily charge | Pays more | Pays less |
Here, the only difference is the agreed capacity. Site A's connection was set up to deliver more power than the site actually uses, so it's in a higher band and pays more every day.
This is where commercial battery storage proves useful.
A battery can help here through what's known as peak shaving. If a battery covers your site's demand spikes so it never draws more than, say, 150kW from the grid, even though demand would otherwise reach 200kW, the site can apply to reduce its Agreed Supply Capacity.
If the capacity comes down, the band drops and so does the daily charge. The battery needs to be doing this reliably, not just occasionally, and the DNO still has to agree to the reduction. But it's one of the few ways a battery can affect the largest part of the TNUoS bill.
The charge itself
The residual is a fixed amount per site per day (£/site/day), and it varies by band. It applies to every meter, every day.
For the 2026/27 charging year, residual charges range from a few pence per day for the smallest sites on low-voltage connections to thousands of pounds per day for the largest EHV and transmission-connected sites. The 2026 increases in TNUoS charges pushed them a lot higher, with rises of 28% to 116% depending on the band.
Because the charge is fixed per day, using less electricity doesn't reduce the residual. The only thing you can do about it is check whether your agreed capacity and connection voltage put you in the right band.
How the locational demand element is calculated
The locational element is typically a few percent of total TNUoS. How it's calculated depends on your meter type.
What determines this are triads. Triads are the three half-hours between November and February when national electricity demand is at its highest. This is when typically cold, dark weekday evenings when heating, lighting, and industrial loads all peak at once.
The problem is that NESO only confirms the triads after the winter is over. You can estimate when they're likely to happen, but you won't know which half-hours were the actual triads until their announcement. So managing triads is educated guesswork, not an exact science.
Here's how the locational element works for each meter type:
| Half-hourly metered | Non-half-hourly metered | |
|---|---|---|
| How the locational element is calculated | Based on your demand during the three triad peaks each winter (£/kW) | Based on how much electricity you use between 4–7pm on weekdays over the year (kWh) |
| When it matters | Cold, dark weekday evenings, November to February | Every weekday afternoon, year-round |
| Can you bring it down? | Yes, by reducing grid import during likely triad periods | Yes, by reducing your 4–7pm weekday consumption |
| How much will you save? | Modest. The locational element is a few percent of total TNUoS | Same. Small compared to the residual |
| Changing soon? | No | If your site is moving to half-hourly metering under the MHHS rollout (2026–2027), you'll switch to the triad-based method. Your supplier can tell you when |
A battery that reduces how much electricity you use during likely triad periods reduces the locational charge for half-hourly sites, but the saving is modest in absolute terms.
Explainer: MHHS (Market-Wide Half-Hourly Settlement) is a national programme that's gradually moving all commercial electricity meters to half-hourly settlement. If your site is currently on a non-half-hourly meter, you'll be switched at some point between 2026 and 2027. When that happens, your locational TNUoS will change from the 4–7pm weekday method to the triad-based method. Your supplier can tell you when your site is due to transition.
Regional zones
Where your site is in GB affects your TNUoS locational charge. There are 14 demand zones, and the further your site is from where most electricity is generated, the more you pay on this element.
Sites in Scotland and northern England pay the least, with some northern zones paying nothing at all. Sites in southern England, especially the south-west and south-east, pay the most because of how far the electricity has to travel further to get there.
For most commercial sites, this is a few percent of total TNUoS. The zone your site is in does matter, but it’s the residual band that matters a lot more. If you want to reduce your TNUoS, reviewing your banding is the best place to start.
Is there a TNUoS calculator?
There is no single universal TNUoS calculator. Your TNUoS cost depends on your residual band, your locational zone, your meter type, and how your supplier treats TNUoS in your contract. Every site is different, which is why a site-specific review will tell you more than any generic calculator.
If you want to look up the raw numbers yourself, NESO publishes the full tariff tables and zone data on its TNUoS charges page. Your DNO or energy supplier can confirm your banding and connection details.
What to check on your own site
Here are five things to check at your own site:
1. Check your banding. If demand has dropped since your connection was set up, your agreed supply capacity is probably too high. Ask your DNO or supplier to review it. If the capacity comes down, your band drops and so does the daily charge.
2. Check your meter type. Half-hourly and non-half-hourly meters are charged differently on the locational element. If your site is moving to half-hourly metering under the MHHS rollout, ask your supplier how the switch will affect your TNUoS.
3. Check your contract. If your TNUoS pass-through, the April 2026 increase is already on your bills. If it's fixed, check whether your supplier allowed enough in their pricing for the 2026/27 tariffs, or whether an adjustment is coming. Look for "pass-through charges" or "third-party charges" in your terms.
4. Check your peak demand. For half-hourly sites: what does your demand look like on cold winter weekday evenings? For non-half-hourly sites: how much electricity are you using between 4pm and 7pm on weekdays? Both affect the locational element, the one part of TNUoS you can actually bring down.
5. Check your wider costs. You can't bring the TNUoS residual down. But DUoS time bands, import timing, solar self-consumption, and trading revenue all respond to how your site uses energy. If you have batteries, solar, or flexible loads, check whether they're set up to reduce your costs automatically or just running on the same schedule they were installed with. Understanding which non-commodity charges you can bring down helps you focus on the right things.
How GridVolt can help
GridVolt's Energy Manager shows you when your site uses the most electricity and what it's costing you, so you can check whether your banding is right and whether your peaks are costing you more than they should. If your site has batteries and solar, it coordinates when they charge and discharge based on your actual tariff rather than a schedule that was set once and never updated.
We don't sell batteries or hardware. The software works with compatible kit already on your site.
Contact GridVolt for a site review and compatibility check. If we can bring your costs down, you'll see how much before you commit to anything.