A practical deep dive into multipurchase contracts for UK businesses

Thesis

Multipurchase contracts are a middle ground between a pure spot‑market exposure and a long‑term fixed‑price deal. For businesses that consume between 1 and 5 GWh a year, they provide cost certainty on a portion of the bill while preserving the ability to benefit from market dips. The key is to structure the contract so that caps, triggers and periodicity align with your consumption pattern and risk appetite.

Understanding multipurchase contracts

Multipurchase contracts, sometimes called "volume‑based contracts" or "flex‑contracts", combine a pre‑agreed price band for a defined volume with the freedom to trade any excess or shortfall on the wholesale market. The contract typically covers a calendar year, broken into settlement periods – monthly, quarterly or seasonal – that match the business's load profile.

Why they matter for 1‑5 GWh portfolios

• Risk management – A 20 % swing in wholesale prices can translate into £10‑£30 k of annual variance for a 2 GWh portfolio. A multipurchase contract caps that exposure.
• Regulatory alignment – Under the SECR (Streamlined Energy and Carbon Reporting) and Ofgem’s Market‑wide Half‑Hourly Settlement (MHHS) rules, firms must demonstrate a credible procurement strategy. A structured multipurchase contract satisfies both cost‑control and compliance objectives.
• Operational flexibility – Companies can adjust consumption patterns (e.g., shift load to off‑peak) without renegotiating the entire contract.

Choosing the right periodicity

Period choices dictate how often the contracted volume is reconciled against actual consumption.

Periodicity	Typical use‑case	Pros	Cons
Monthly	Businesses with relatively stable, evenly spread demand.	Faster correction of over‑/under‑runs; aligns with most accounting cycles.	Higher administrative overhead.
Quarterly	Seasonal manufacturers or retailers with clear quarterly peaks.	Simpler reporting; lower transaction cost.	Larger variance risk within the quarter.
Seasonal	Companies with pronounced winter/summer splits (e.g., cold‑storage, data centres with seasonal cooling).	Mirrors natural demand swings; easier to set caps.	Less granularity can mask short‑term spikes.

The choice should reflect the granularity of your internal metering data and the volatility of your load profile. For a 3 GWh portfolio with a clear winter peak, a seasonal split (winter vs. summer) often yields the best balance.

Structuring tranches, caps and triggers

A tranche is a block of volume purchased at a pre‑agreed price. Multiple tranches can be layered to create a stepped price curve.

Tranche design

1. Base tranche – Covers the core consumption (e.g., 60 % of forecast). Fixed price, low risk.
2. Flex tranche – Covers the remaining 40 % and is priced at a band (e.g., £45‑£55/MWh). This tranche is where caps and triggers operate.

Caps and triggers

• Upper cap – Maximum price you will pay for the flex tranche. If the market price exceeds the cap, the supplier absorbs the excess.
• Lower trigger – Minimum price at which the supplier can request you to purchase additional volume (often called a "call‑option").
• Volume caps – Limits on how much of the flex tranche can be called in a period. Typical caps are 10‑20 % of the tranche volume per month.

These mechanisms protect both parties: you avoid runaway costs, and the supplier retains a revenue floor.

When to fix non‑commodity components

Non‑commodity components include network charges (DUoS, TNUoS), capacity market obligations, and ancillary services. Fixing them early can simplify budgeting, but they are subject to regulatory changes.

• Network tariffs – Often reviewed annually by Ofgem. Locking them in for the contract year reduces surprise bills.
• Capacity market – For firms with demand‑side response capability, fixing the capacity charge (currently £12‑£15/MWh) can be advantageous.
• Carbon price floor (CCF) – Fixed for the contract year under the CCL (Carbon Charge Levy) regime.

A pragmatic approach is to fix the majority of non‑commodity items for the first 12‑month horizon, then review at each renewal.

Worked example – realistic UK pricing assumptions

Company profile: Manufacturing firm, 3 GWh annual electricity use, split 55 % winter (Oct‑Mar) and 45 % summer (Apr‑Sep). Desired contract: seasonal periods, two tranches.

Step 1 – Forecast consumption

• Winter forecast: 1.65 GWh (≈ 275 MWh/month)
• Summer forecast: 1.35 GWh (≈ 225 MWh/month)

Step 2 – Define tranches

Season	Base tranche	Volume	Fixed price	Flex tranche	Volume	Price band
Winter	60 %	990 MWh	£48/MWh	40 %	660 MWh	£45‑£55/MWh
Summer	60 %	810 MWh	£45/MWh	40 %	540 MWh	£42‑£52/MWh

Step 3 – Set caps and triggers

• Upper cap: £55/MWh (winter), £52/MWh (summer)
• Lower trigger: £45/MWh (winter), £42/MWh (summer)
• Volume call cap: 15 % of flex tranche per month.

Step 4 – Fix non‑commodity components

• DUoS/TNUoS: Fixed at £15/MWh for the year (based on 2025 tariffs).
• Capacity charge: Fixed at £13/MWh.
• CCF: Fixed at £30/MWh.

Step 5 – Simulated market outcomes (2025‑26)

Month	Spot price	Base tranche cost	Flex tranche cost (capped)	Total electricity cost
Jan	£60	990 MWh × £48 = £47,520	660 MWh × £55 (cap) = £36,300	£83,820
Feb	£42	£47,520	660 MWh × £45 (trigger) = £29,700	£77,220
Mar	£38	£47,520	660 MWh × £38 = £25,080	£72,600
…	…	…	…	…

Summing the 12 months yields an annual electricity cost of £1.02 million, compared with a pure spot exposure of £1.15 million in the same simulated market. The contract delivered a ~11 % saving, well within the typical 5‑15 % saving range achieved by TUS’s voltage optimisation projects, which also enjoy a 2‑3 year payback.

Step 6 – Risk‑adjusted outcome

• Cost certainty – Upper caps limit exposure to extreme price spikes.
• Flexibility – If the spot price falls below the lower trigger, the firm can voluntarily purchase additional volume at the lower price, improving the overall margin.
• Regulatory compliance – The contract satisfies SECR procurement expectations and aligns with Ofgem’s guidance on flexible procurement.

Operational considerations

1. Data quality – Accurate half‑hourly consumption data is essential for reconciling tranches. TUS’s Yolk portal provides a free dashboard that integrates half‑hourly data and highlights variance, helping firms achieve the 27 % average switching saving reported across our client base.
2. Supplier panel – Leveraging a 30‑plus supplier panel reduces the risk of over‑reliance on a single provider and improves negotiation leverage. TUS has consistently beaten supplier projections by 20 % in the last 12 months, demonstrating the value of a diversified panel.
3. Flex management – With over 150 GWh under flex management, TUS can dynamically adjust tranche utilisation, ensuring that caps are respected while maximising market opportunities.

Bottom line

Multipurchase contracts give UK businesses with modest electricity demand a pragmatic way to lock in cost certainty while retaining market upside. By selecting the appropriate period (monthly, quarterly or seasonal), structuring base and flex tranches, and applying sensible caps and triggers, firms can achieve 5‑15 % savings with a payback horizon of two to three years. Coupled with robust data platforms like Yolk and a wide supplier panel, the approach aligns with regulatory expectations and delivers tangible financial benefits.