Your Business Electricity Bill Explained: The Charges You Can Actually Reduce
A commercial electricity bill contains a surprising number of separate charges, most of which are presented without explanation. For a finance or operations manager trying to understand where the money is going and which parts can be reduced, that lack of transparency is genuinely unhelpful. Some of these charges are fixed by the grid and by government policy. Others are directly influenced by how efficiently the site uses electricity, and those are the ones worth focusing on.
This guide breaks down the main components of a business electricity bill, identifies which can be reduced and how, and gives a plain answer to the question that brings a lot of people here: does the voltage your site runs at actually affect what you pay.
The Main Parts of a Commercial Electricity Bill
Commercial electricity bills vary in layout and terminology between suppliers, but the underlying charges fall into a consistent set of categories.
Unit rate and consumption
The unit rate is the cost per kilowatt-hour (kWh) of electricity consumed. It is the most visible line on the bill and the one most people focus on when comparing suppliers. The total consumption charge is the unit rate multiplied by the number of units consumed in the billing period. For sites on half-hourly metering, the rate may vary by time of day under a time-of-use tariff.
Standing, availability and capacity charges
These are fixed charges that reflect the cost of maintaining a connection to the grid at a given capacity. They are based on the maximum demand the site is contracted for, typically in kilovolt-amperes (kVA) rather than kilowatts. A site that draws a high peak demand pays more for availability than one with a flatter load profile, even if total consumption is similar. Where a site’s power factor is poor, the kVA figure is inflated relative to the useful power actually consumed.
Reactive power and kVArh charges
These appear on bills for commercial and industrial sites with a poor power factor, measured in kilovolt-ampere reactive hours (kVArh). They represent the cost of the reactive power the grid has to supply to the site above an agreed threshold. They are common on sites with significant motor, compressor, HVAC and refrigeration loads, and they are often overlooked because the line item is not self-explanatory. The detail on what these charges are and how they arise is covered in the reactive power and kVA charges guide.
Distribution use of system (DUoS) charges
DUoS charges recover the cost of distributing electricity across the local network from the transmission system to the site. They are set by the distribution network operator and passed through by the supplier. They vary by region and time of day under red, amber and green band pricing, and they are largely outside the site’s control beyond time-shifting consumption where possible.
Transmission network use of system (TNUoS) charges
These recover the cost of the high-voltage transmission network. For larger consumers, the Triad system applies: the highest demand periods on three winter weekdays each year set the TNUoS charge for the following year. Active demand management around forecast Triad periods can reduce this for eligible sites, but it requires real-time monitoring and a trading relationship with the supplier.
Government levies and policy costs
A portion of every commercial electricity bill goes towards government energy policy obligations, including the Renewables Obligation, Feed-in Tariff legacy costs, Contracts for Difference, and the Capacity Market. These are non-negotiable and cannot be reduced by operational changes at the site level.
VAT at 20% applies to most commercial electricity. Climate Change Levy (CCL) also applies to most commercial consumers, though exemptions are available for certain renewable supplies and eligible processes.
The Charges You Can Actually Reduce
Of the categories above, the consumption charge, reactive power charges, and kVA availability charges are the ones a site can actively reduce through the right interventions. The rest are set externally.
Reducing consumption through voltage optimisation
The consumption charge is the largest line on most commercial bills, and it is directly reduced by cutting how much electricity the site draws. Voltage optimisation addresses over-voltage waste: the UK grid delivers at an average of around 242 volts, but most equipment is designed for 220 volts, and the gap is wasted energy. Bringing the supply down to the correct level typically cuts consumption by 7 to 12%. On a site spending £100,000 a year on electricity, that is £7,000 to £12,000 back annually, with payback usually under 18 months.
Removing reactive power charges through power factor correction
Reactive power charges are among the most avoidable lines on a commercial bill. Power factor correction equipment compensates for reactive power demand on-site, bringing the power factor towards 1.0 and eliminating or significantly reducing the kVArh charge. It also reduces the kVA peak demand figure, which can lower availability charges. For sites currently paying reactive power charges, power factor correction is typically the highest-return intervention available.
Reducing losses through harmonic filtering
Sites with variable speed drives, large motors, and other non-linear loads generate harmonic distortion that causes additional losses in cables, transformers and switchgear. These losses show up as increased consumption without corresponding useful output. Harmonic filtering reduces distortion at source, cutting losses and in some cases reducing maximum demand peaks. It is not relevant for every site, but where harmonic distortion is significant, it is part of the supply-side efficiency picture.
The Charges You Mostly Cannot Reduce
Honesty on this point matters, because a lot of energy advice glosses over it. DUoS, TNUoS, government levies and CCL are set by the network, the regulator and government policy. No piece of on-site equipment changes them. They can be managed at the margin through time-of-use tariff optimisation and Triad avoidance for eligible sites, but for most commercial and industrial businesses they are a fixed cost of the connection.
Standing charges are also largely fixed by the contracted capacity. A site can reduce its contracted capacity if its demand profile genuinely supports a lower tier, but this is an administrative change with the supplier rather than an operational one, and reducing capacity below what the site actually needs creates risk.
What this means in practice is that the controllable portion of a commercial electricity bill is the consumption and power quality charges. Reducing those is where the return on investment is most predictable and most straightforward to evidence.
Does Voltage Affect Your Electricity Bill?
Yes, in two distinct ways, and they are often confused.
The first is over-voltage consumption waste. If the site is receiving supply at significantly above 220 volts, equipment draws more energy than it needs to operate. That excess shows up directly in the consumption charge. Reducing the supply voltage to the correct level removes the waste and reduces the unit consumption figure. This is the mechanism behind voltage optimisation savings.
The second is the question behind the search queries that drive a lot of traffic to this topic: does a low voltage increase the bill? For most commercial equipment, a lower supply voltage increases the current drawn for the same power output, which can increase losses. The detail on how voltage levels translate to consumption and cost, and the scenarios where both high and low voltage create waste, is covered in the how voltage reduction saves money guide.
Where to Start
Pull up a recent electricity bill and look for three things. First, the total annual spend: this sets the scale of the opportunity. Second, any kVArh or reactive power line items: if they are present and material, power factor correction is almost certainly worth investigating. Third, the kVA availability or maximum demand figure: if this seems high relative to the site’s actual operating load, it is worth understanding why.
From there, the free savings calculator gives an initial estimate of what voltage optimisation could save based on annual spend and sector. A power quality survey then produces the site-specific figures: measured incoming voltage, power factor, harmonic distortion, and a projection of the saving achievable from correction, accurate enough to build a business case from.
Frequently Asked Questions
What are the biggest charges on a business electricity bill?
For most commercial and industrial sites, the consumption charge (unit rate multiplied by kWh used) is the largest single component. Availability or capacity charges based on kVA maximum demand are also significant, particularly for sites with a poor power factor that inflates the kVA figure. Network costs (DUoS and TNUoS) and government levies make up a meaningful share of the total but cannot be reduced by on-site action.
Which energy charges can a business reduce?
The consumption charge, reactive power and kVArh charges, and kVA availability charges are the most directly reducible through on-site intervention. Voltage optimisation reduces consumption. Power factor correction reduces or eliminates reactive power charges and lowers the kVA demand figure. Harmonic filtering reduces losses on sites with significant non-linear load. The network and policy charges are set externally and cannot be changed at the site level.
Does voltage affect my electricity bill?
Yes. If the incoming supply voltage is significantly above the equipment design voltage, the excess is wasted as heat and increases consumption. Voltage optimisation corrects this and reduces the consumption charge directly. A supply voltage that is too low can also increase current draw and losses, though this is a less common issue on the UK grid. A voltage dependency survey will establish the incoming voltage profile and quantify the saving available.
What are reactive power charges on a business electricity bill?
Reactive power charges, labelled kVArh or excess reactive on a bill, are applied when a site draws more reactive power from the grid than an agreed threshold. They are caused by inductive loads: motors, compressors, HVAC, refrigeration. They are reduced or eliminated by power factor correction. The full explanation of what reactive power is and how the charge arises is in the reactive power and kVA charges guide.
If you want to understand which charges on your bill are avoidable and what the saving would be, the free savings calculator is a useful starting point. To get site-specific figures, contact our team to arrange a power quality survey. It will tell you clearly which charges you are paying that you do not need to be, and what it would take to remove them.
