From 1st April, one of the least understood costs on your electricity bill changed. This is why it matters.

From 1^st April, many organisations across the UK will see another noticeable shift in the price of their electricity bill, independent of ongoing changes to wholesale costs, and not because they are using more power.

Instead, one of the most significant non-commodity charges on the bill, TNUoS, resets for the new charging year. For many this will be one of the least visible changes on the invoice, but one of the most important.

That’s because TNUoS, short for Transmission Network Use of System charges, helps fund the operation, maintenance and upgrade of the national electricity transmission network. In simple terms, it is one of the costs of keeping the UK’s grid running and future-fit, and one of several non-commodity charges that appear on energy bills.

And from 1^st April, the new 2026/27 charges come into force which, for some organisations, means a meaningful increase in cost. For others, it may also mean a change in how their site is banded.

Why this matters now

A common misconception is that the electricity bill rises and falls mainly with wholesale market prices.

But that’s no longer the full picture. An increasing share of electricity costs now sits outside the unit rate, in the form of network, balancing and policy costs.

TNUoS is one of the most material of these, and in many cases, it is now a significant standing charge that sits outside day-to-day consumption. That means using less electricity doesn’t always reduce exposure in the way you might expect.

This is particularly important as the April reset takes effect, because the annual tariff refresh can result in substantial year-on-year movement. Current market analysis suggests average business charges are rising by around 60% to 64% for 2026/27.

For finance and operational teams, this is exactly why invoice scrutiny in April and May is so important.

The part many organisations miss: banding

Alongside the annual tariff reset, TNUoS charges are also influenced by site banding. In plain English, this means your site is placed into a charging category based on factors such as voltage level and agreed capacity.

This is where organisations can sometimes end up paying more than necessary. We regularly see sites where the agreed supply capacity is materially higher than actual operational demand; this can place the site in a higher residual charging band than it needs to be, resulting in a higher cost levied on the bill.

Equally, organisations expanding electrification, for example through EV charging, plant upgrades or heat electrification, can unintentionally push a site closer to or even over a band threshold, again having an impact on the related cost being added to the bill.

Energy bill spring cleaning

First, it’s vital to check your April invoices carefully, and to not just focus on the unit rate, but to look specifically at:

• TNUoS charges – Review these first to understand the impact of the reset on your annual transmission costs and whether this year’s uplift is materially affecting your total electricity spend.
• Standing charges – Check for any increase in fixed daily costs, as these can quietly raise the baseline cost of running a site even where consumption remains stable.
• Residual demand charges – Review these to identify whether your site’s fixed network cost exposure has increased, as these charges are often driven by banding and capacity rather than actual usage.
• Changes in site banding or capacity assumptions – Scrutinise any changes here carefully, as a shift in classification or contracted capacity can create a disproportionate increase in annual fixed charges and materially affect budget forecasts.

The next step is to review agreed supply capacity against actual demand data; this is where half-hourly consumption data becomes critical. If peak demand is materially below contracted capacity, there may be an opportunity to review capacity with the Distribution Network Operator and reduce future cost exposure.

However, this also needs to be approached strategically, because reducing capacity too far can create future constraints, particularly if electrification projects are planned.

The last step is to think beyond procurement. That’s because this is no longer just a buying challenge, but an energy system design challenge. Put simply, onsite solar, battery storage, demand flexibility and tariff optimisation all play a role in reducing exposure to network and non-commodity costs over time, by reducing consumption and increasing flexibility.

The bigger shift

The most important point to take from this is that energy costs are becoming increasingly structural. For many organisations, the real opportunity isn’t just buying energy better, but to understand what sits underneath the bill and actively design exposure more intelligently.

This is exactly why non-commodity costs now deserve far more internal attention than they have historically received. The new charging year is a prime opportunity to take stock, and to take action to reduce exposure.

Andrew Donald, Business Development Manager – Equity Energies