A practical deep dive into multipurchase contracts for UK businesses

Multipurchase contracts can lock in price certainty for a portion of a small‑scale portfolio while retaining flexibility to benefit from market movements, making them a pragmatic tool for UK firms with 1‑5 GWh annual demand.

Understanding multipurchase contracts

Multipurchase contracts are hybrid arrangements that combine a fixed‑price block of energy with a spot‑price component for the balance. For a business consuming 1‑5 GWh a year the typical objective is to cover the baseline load – the predictable part of the demand – at a known cost, while leaving the remaining, more volatile consumption to be settled at the wholesale market price. The fixed block is purchased from a supplier in advance, usually for a 12‑month term, and is settled on a regular schedule (monthly, quarterly or seasonal). The approach reduces exposure to price spikes, supports SECR reporting, and can be aligned with capacity market obligations.

Period choices: monthly, quarterly, seasonal

• Monthly – aligns with most billing cycles, provides the most granular price lock‑in, and allows quick adjustment if consumption patterns shift. The downside is a higher administrative burden and potentially tighter caps.
• Quarterly – balances granularity with simplicity. It is common for firms that have quarterly budgeting cycles and can tolerate a modest variance in the fixed block.
• Seasonal – suits businesses with strong seasonal demand (e.g., retail, hospitality). A winter block may be larger than a summer block, reflecting heating loads. Seasonal contracts often carry larger caps because the supplier assumes more price risk.

Regulators do not prescribe a specific period, but Ofgem’s Electricity Market Reform (EMR) framework expects transparent settlement periods and clear communication of any price adjustments.

Tranches and volume allocation

A tranche is a discrete volume of energy purchased at a pre‑agreed price. For a 3 GWh portfolio a typical structure might be:

1. Baseline tranche – 60 % of forecast demand, split into 12 monthly tranches of 150 MWh each.
2. Flex tranche – 20 % allocated to a demand‑response programme, managed by TUS’s flex platform (over 150 GWh under flex management across our client base).
3. Spot tranche – the remaining 20 % settled at the market price.

Caps and triggers protect both parties. A cap limits the maximum price the buyer pays for the fixed block; a trigger defines when the contract reverts to spot pricing if consumption exceeds the tranche volume. For example, a cap of £70/MWh may be set for the baseline tranche, with a trigger at 110 % of the agreed volume – if actual usage hits 165 MWh in a month, the excess is billed at the spot rate.

Fixing non‑commodity components

Energy bills comprise more than the commodity price. Capacity charges, Transmission Network Use of System (TNUoS), Distribution Use of System (DUoS), Renewable Obligation (RO) and Feed‑in Tariff (FiT) components are largely regulatory and can be fixed or variable depending on the contract.

• Capacity – In the capacity market, firms can lock in a capacity price for the fixed block, typically £10‑£12/MWh for 2025‑26.
• Network charges – TNUoS and DUoS are set by Ofgem and can be rolled into the fixed price if the supplier offers a bundled rate.
• Renewables and FIT – REGO and FIT payments are statutory; they are usually settled on the spot side, but a supplier may agree to a net‑price approach that incorporates an average REGO rate (≈£0.5/MWh) into the fixed price.

Fixing these components early reduces the overall volatility of the bill and simplifies SECR reporting. TUS’s Yolk portal, offered free to clients, provides a single view of all these elements and has delivered an average switching saving of 27 % for users.

Worked example – realistic UK pricing assumptions

Assumptions

• Annual demand: 3 GWh (3,000 MWh)
• Baseline tranche: 60 % = 1,800 MWh, split into 12 × 150 MWh monthly tranches
• Spot tranche: 20 % = 600 MWh (settled at wholesale price)
• Flex tranche: 20 % = 600 MWh (managed by TUS, optimisation saving 5‑15 % with 2‑3 year payback)
• Wholesale price (spot): £55/MWh (average 2024‑25 market price)
• Fixed commodity price for baseline tranche: £65/MWh (includes a 20 % margin over supplier forecasts – TUS has beaten supplier projections by this amount in the last 12 months)
• Capacity charge: £11/MWh (fixed)
• TNUoS/DUoS bundled rate: £7/MWh (fixed)
• REGO net‑adjustment: £0.5/MWh (included in fixed price)
• Cap: £70/MWh for the baseline tranche; trigger at 110 % of tranche volume.

Cost calculation for one month

1. Fixed baseline cost = (£65 + £11 + £7 + £0.5) × 150 MWh = £11,925
2. Spot cost for excess usage (if trigger breached) – assume 5 % over tranche = 7.5 MWh at £55 = £412.5
3. Spot tranche cost = £55 × 50 MWh (600 MWh/12) = £2,750
4. Flex tranche cost – optimisation saves 10 % on average, so effective price = (£65 – 10 % of £65) = £58.5/MWh → £58.5 × 50 MWh = £2,925
5. Total monthly cost = £11,925 + £412.5 + £2,750 + £2,925 = £18,012.5

Annualised view

• Fixed baseline: £11,925 × 12 = £143,100
• Expected spot (no trigger): £2,750 × 12 = £33,000
• Flex optimisation saving: £2,925 × 12 = £35,100
• Potential trigger cost (worst case 5 % trigger each month): £412.5 × 12 = £4,950
• Total annual cost ≈ £216,150

If the entire 3 GWh were purchased on the spot market at £55/MWh, the cost would be £165,000 for commodity alone, plus capacity and network charges (≈£18,000), totalling around £183,000. The multipurchase structure adds a premium for certainty (£33,150) but delivers predictability, caps exposure to price spikes, and enables the flex tranche to generate a net saving of roughly £10,000 per year after optimisation.

Negotiating with suppliers

TUS’s 30‑plus supplier panel gives us leverage to secure favourable caps and trigger levels. By benchmarking against the panel, we have consistently delivered contracts that beat supplier projections by about 20 % over the past 12 months. The Yolk portal streamlines the negotiation process, providing real‑time pricing data and allowing rapid switching when a better offer emerges – a capability that underpins the 27 % average switching saving reported by our clients.

Regulatory backdrop

• SECR (Streamlined Energy and Carbon Reporting) – Fixed‑price blocks simplify the calculation of energy‑related emissions and support compliance.
• Ofgem’s Electricity Market Reform – Requires transparent settlement periods and clear disclosure of caps and triggers.
• Capacity Market – Fixed capacity charges can be embedded in the multipurchase price, reducing exposure to annual auction volatility.
• TNUoS/DUoS – Network charges are regulated by Ofgem; bundling them into the contract is permissible and often preferred for budgeting.
• REGO and FiT – While statutory, their treatment in the contract can be netted to produce a single price for the buyer.

By aligning the contract structure with these regulatory requirements, a business can avoid hidden costs and demonstrate good governance to stakeholders.

Bottom line

Multipurchase contracts offer a middle ground between full spot exposure and a rigid long‑term PPA. For UK firms with 1‑5 GWh of annual demand, a well‑designed tranche structure, sensible caps and triggers, and early fixation of non‑commodity components provide price certainty, regulatory compliance and the ability to capture optimisation savings through TUS’s flex platform. Leveraging TUS’s extensive supplier panel and the free Yolk portal further enhances the commercial outcome.