I&C (Industrial & Commercial)
A classification for larger, more complex business energy customers - typically manufacturing plants, hospitals, data centres, or multi-site retail chains. I&C customers usually have half-hourly metering, consume over 100,000 kWh annually, and may have on-site generation, battery storage, or demand-side response capabilities. Unlike typical SMEs who buy energy as a simple commodity, I&C customers often require strategic energy management and may benefit from traditional broker services.
Example:
A 24/7 factory with half-hourly meters, rooftop solar, and a 500kW demand profile is classified as an I&C customer. They need unbundled contracts and peak avoidance strategies that most SMEs don't require.
Microbusiness
A small business that qualifies for enhanced consumer-style protections under Ofgem regulations. To qualify, a business must meet at least one of these criteria: fewer than 10 employees, annual turnover or balance sheet under €2 million, or annual energy consumption under 100,000 kWh (electricity) or 293,000 kWh (gas). Microbusinesses receive clearer contract terms, protection from unfair practices, and access to the Energy Ombudsman for disputes.
Example:
A coffee shop with 4 employees using 25,000 kWh per year qualifies as a Microbusiness and can complain to the Energy Ombudsman if treated unfairly.
Ofgem
The Office of Gas and Electricity Markets - the UK's independent energy regulator. Protects consumers by setting rules for energy suppliers, managing licences, and enforcing market standards. Does not set energy prices directly.
Example:
Ofgem introduced the energy price cap for domestic customers in 2019 and TPI transparency rules for business energy in 2024.
Wholesale Energy Price
The price energy suppliers pay to purchase gas and electricity from generators and traders on the wholesale market before selling it to consumers. Fluctuates based on supply, demand, weather, and geopolitical factors. Major component of your energy bill.
Example:
When wholesale gas prices spiked in 2022, business energy rates increased significantly.
Market-Wide Half-Hourly Settlement (MHHS)
A major regulatory programme requiring all UK electricity meters to be settled based on actual half-hourly consumption data rather than estimated profiles. Migration opened October 2025 with mass rollout from April 2026. Delivered by Elexon under Ofgem direction. Creates 'winners' (off-peak users) and 'losers' (peak-time users) as pricing shifts from averages to actuals. By January 2027, businesses without smart meters may be blocked from fixed-rate contracts.
Example:
Under MHHS, a bakery starting at 4 AM pays less than a restaurant firing up ovens at 6 PM - even if both use the same total kWh.
DNO (Distribution Network Operator)
The company responsible for operating and maintaining the local electricity distribution network in your area. There are 14 DNO regions across Great Britain, owned by six different groups. Your DNO delivers electricity from the National Grid to your premises and charges DUoS fees for this service.
Example:
UK Power Networks is the DNO for London and the South East; Scottish Power Energy Networks covers central and southern Scotland.
NESO (National Energy System Operator)
The organisation responsible for operating Britain's electricity and gas systems in real-time, ensuring supply meets demand every second of every day. Formerly part of National Grid, NESO became an independent public corporation in 2024. Energy suppliers must notify NESO of their expected demand, and NESO uses the Balancing Mechanism to correct any mismatches between supply and demand.
Example:
Your supplier tells NESO they expect their customers to use 500MW between 5-6pm. If actual usage is 520MW, NESO activates the Balancing Mechanism and the supplier pays imbalance charges.
EAC (Estimated Annual Consumption)
Your forecasted electricity usage for the next 12 months, measured in kWh. Suppliers use your EAC to calculate quotes and determine how much energy to purchase on the wholesale market. EAC is typically based on historical meter readings, but can be adjusted for expected changes in your business. Getting your EAC wrong can trigger Volume Tolerance penalties if actual usage differs significantly from the estimate.
Example:
Based on last year's readings, your EAC is 25,000 kWh. Your supplier commits to buying this volume upfront. If you only use 18,000 kWh (28% under), you may face Take-or-Pay charges.
AQ (Annual Quantity)
Your forecasted gas usage for the next 12 months, measured in kWh. The gas equivalent of EAC (Estimated Annual Consumption) for electricity. Your AQ is calculated by your gas transporter based on historical meter readings and is used by suppliers to quote prices and purchase gas on the wholesale market. Found on your gas bill, typically shown alongside your MPRN. If your business circumstances change significantly (expansion, downsizing, efficiency improvements), you can request an AQ amendment from your supplier.
Example:
Your gas bill shows an AQ of 45,000 kWh. If you've installed a new efficient boiler that reduces usage by 20%, you should request an AQ amendment to 36,000 kWh to avoid Volume Tolerance penalties.
System Sell Price (SSP)
The price at which energy suppliers can sell excess electricity back to the grid when they have bought more than their customers used. The System Sell Price is typically lower than the System Buy Price (what suppliers pay to buy extra power), meaning suppliers lose money when they're 'long' on power. This price asymmetry is why Volume Tolerance clauses exist - suppliers need protection against customers using significantly less than forecast.
Example:
Your supplier bought power at 20p/kWh for you. You used 20% less than expected, so they had to sell the excess back at the System Sell Price of 12p/kWh - an 8p/kWh loss on every unused unit.
DUoS (Distribution Use of System) Charges
Fees charged by your local distribution network operator (DNO) for transporting electricity through the local network to your premises. Based on your consumption and demand. Passed through to you by your supplier.
Example:
Your bill shows £78 in DUoS charges for using the local electricity network this month.
TNUoS (Transmission Network Use of System) Charges
Fees for using the national high-voltage electricity transmission network to transport power across the UK. Charged to larger business users (typically HH metered). Varies by location and time of use.
Example:
Northern businesses often pay lower TNUoS charges than those in the South due to proximity to generation.
NTS (National Transmission System)
The high-pressure gas pipeline network that transports natural gas across Great Britain, operated by National Gas Transmission. NTS charges cover the cost of moving gas from entry points (terminals, storage, interconnectors) to local distribution networks. These charges are typically bundled into your gas unit rate but may appear as separate line items on detailed commercial invoices.
Example:
Your detailed gas invoice shows 'NTS Entry Capacity' and 'NTS Exit Capacity' charges - these are the costs of using the national gas transmission network.
LDZ (Local Distribution Zone)
One of 13 geographic regions in Great Britain where gas is distributed through lower-pressure pipelines from the National Transmission System to end customers. Each LDZ is operated by a Gas Distribution Network (GDN) and has its own transportation charges. LDZ charges are typically bundled into your gas unit rate but may appear separately on detailed invoices as 'LDZ Capacity' or 'LDZ Commodity' charges.
Example:
Your business is in the 'North West' LDZ operated by Cadent. The LDZ charges on your bill reflect the cost of distributing gas through the local network to your premises.
BSUoS (Balancing Services Use of System) Charges
Charges levied by the National Energy System Operator (NESO) to recover the costs of balancing electricity supply and demand in real-time. From October 2025, BSUoS rises from 1.074p/kWh to 1.569p/kWh - a 46% increase. These costs flow through to business bills via supplier tariffs.
Example:
The October 2025 BSUoS increase adds approximately £123 per year to a business using 25,000 kWh annually.
Climate Change Levy (CCL)
A government tax on business energy consumption introduced under the Finance Act 2000 to incentivise carbon reduction. The CCL appears as a separate line item on business energy bills. Current rates (2025-2026) are 0.775p/kWh for electricity and 0.672p/kWh for gas. Exemptions apply to charities for non-business use, businesses with Climate Change Agreements, very low energy users under de minimis thresholds, and renewable energy backed by REGOs.
Example:
A business using 50,000 kWh of electricity annually pays approximately £387.50 in CCL (50,000 × 0.775p), plus VAT on top.
MIC (Maximum Import Capacity)
The maximum amount of electricity (measured in kVA or kW) that your premises is authorised to draw from the network at any moment. Set by agreement with your Distribution Network Operator (DNO). Higher MIC means higher capacity-related standing charges (TNUoS/DUoS). Businesses that have downsized but kept their original MIC may be overpaying.
Example:
Reducing your MIC from 100 kVA to 50 kVA after downsizing could save £1,000-£3,000 per year in capacity charges.
Availability Charge
A fixed charge based on your agreed Maximum Import Capacity (MIC), reflecting the network capacity reserved for your site. Set by your DNO and passed through by suppliers. Unlike unit rates and standing charges, brokers cannot add commission to availability charges - though suppliers may mark them up before passing to customers.
Example:
Your availability charge of £15/month reflects the 70 kVA capacity reserved for your warehouse on the local network.
Cost Allocation and Recovery Review (CARR)
A major Ofgem review launched in July 2025 examining how costs are shared across the energy system. The review looks at wholesale costs, network costs, policy costs, and supplier margins to determine whether the current allocation (roughly 60% to non-domestic, 40% to domestic) remains appropriate. Exploring alternatives including time-of-use pricing, regional pricing, and capacity-based charges.
Example:
Under CARR reforms, businesses with smart meter data proving off-peak usage may pay lower network charges than those billed on 'average' assumptions.
TPI Registration
The upcoming requirement for all Third Party Intermediaries (brokers, consultants, switching platforms) to register with Ofgem before operating in the energy market. Once Ofgem is formally appointed as TPI regulator, existing TPIs will have a 12-18 month 'sunrise period' to register and demonstrate compliance with new conduct principles and rules.
Example:
Your current broker must register with Ofgem by 2027 or face being banned from operating. Ask them about their registration plans.