TNUoS and DUoS charges explained
How TNUoS and DUoS charges may affect your business energy bill – and what you can do about it.
Transmission Network Use of System (TNUoS) and Distribution Use of Service (DUoS) charges form a significant part of your business energy bill.
In this article, we explain what TNUoS and DUoS charges are, what they pay for, how they are structured, and whether it’s possible to reduce your business’ bill.
What are TNUoS and DUoS charges and what do they pay for?
TNUoS charges pay to build, maintain and operate the UK’s onshore and offshore transmission network. These high-voltage ‘motorways’ of the energy system carry power from generation sites to interconnectors with other countries and to the local, lower-voltage network that serves homes and businesses.
DUoS charges fund that lower-voltage network – the ‘local roads’ that take the power the rest of the way to end users.
In April 2026, TNUoS charges increased significantly to fund upgrades to Britain’s ageing transmission infrastructure and to bring new renewable energy assets online as the country accelerates its shift to a lower carbon grid.
How are TNUoS and DUoS charges collected?
Both TNUoS and DUoS charges are collected through a fixed charge and a usage based charge.
TNUoS charges
Fixed charge: The majority of TNUoS charges are collected through your daily electricity standing charge. This fixed charge is calculated based on your meter type and your capacity / consumption band.
Usage-based charge: A smaller proportion of TNUoS charges is based on your electricity usage during peak periods:
- For domestic or small non-domestic meters without a Maximum Import Capacity (MIC) agreement, this is based on an estimate of how much electricity your business uses between 4pm and 7pm every day of the week. Because this is an estimate, it is billed as a fixed amount through your electricity standing charge.
- For larger non-domestic meters with an agreed capacity limit, this is based on your average electricity consumption during the ‘triad’ periods – the three half-hourly periods during the winter months when demand on the electricity grid was at its highest. This may appear as a separate line item on your bill. Once the winter period is over, there may be a reconciliation between the forecast charges and your actual consumption, which could result in an additional charge or a credit.
DUoS charges
Fixed charge: Most meters will have a fixed daily DUoS charge that applies to their meter and varies depending on the meter type and region. Larger meters that have an agreed capacity limit with their distribution network will also receive a fixed capacity charge which is applied daily. The higher the capacity, the higher the charge.
Usage-based charge: Times of the day are split into different tiers depending on how much demand is expected on the grid. Using power in peak periods is much more expensive than using power in off-peak periods. Larger meters that have an agreed capacity limit with their distribution network will also incur extra costs if they exceed this limit.
How can you reduce your TNUoS and DUoS charges?
The vast majority of TNUoS and DUoS charges are collected through fixed banded charges and cannot be avoided entirely. However, there are steps businesses can take to reduce their exposure:
Install on-site generation and battery storage: Generating your own electricity on site and storing off-peak power in battery storage will reduce your overall reliance on the national grid, lowering your energy costs. It will also lower your exposure to peak usage-based charges.
Review your capacity band with your DNO: Your fixed TNUoS and DUoS charges are mostly determined by your Maximum Import Capacity (MIC) limit – the maximum amount of power your site is permitted to draw at any one time. If your peak demand is consistently lower than your agreed capacity limit, you may be able to apply to your Distribution Network Operator (DNO) to reduce it. On-site renewables and battery storage can make this more achievable by smoothing out peak demand. Please note, if you need to raise your capacity limit again, it may come at a significant expense.
Negotiate your tariff structure: Some suppliers are able to pass through TNUoS and DUoS charges as a separate, itemised cost on your bill. This gives you greater visibility and allows you to actively manage and benefit from demand-side optimisations.
Understanding how these charges work puts your business in a stronger position to manage them. While most of the charge is fixed, there are meaningful savings available for businesses that review their capacity arrangements and invest in on-site generation or storage.
