Procurement

A practical deep dive into multipurchase contracts for UK businesses

Multipurchase contracts let organisations with 1‑5 GWh of annual demand lock in price bands while retaining flexibility to shift volumes across periods. This article explains the mechanics – period choices, tranches, caps, triggers and the optimal moment to fix non‑commodity components – and walks through a realistic UK‑based worked example.

By TUS Trade Desk — Commercial Energy Consultants•Published 13 October 2026•6 min read

The thesis

For UK businesses that consume between 1 and 5 GWh a year, a well‑designed multipurchase contract can deliver up to 15 % cost certainty while preserving the ability to respond to market swings. The key is to structure the contract so that commodity exposure is limited to the most volatile slices of the price curve, and the non‑commodity elements – capacity, network and ancillary services – are fixed when they are cheapest.

Why multipurchase contracts matter

The UK electricity market is increasingly volatile. The Ofgem‑run Capacity Market, the Carbon Price Floor and the ongoing transition to low‑carbon generation create price spikes that can double the wholesale price in a single week. For a finance director, an unexpected spike can erode EBITDA and breach internal cost‑of‑energy targets set under the SECR (Streamlined Energy and Carbon Reporting) framework.

Multipurchase contracts, sometimes called "basket" or "portfolio" contracts, allow you to purchase a defined volume of electricity at pre‑agreed price bands across several time‑slices. The approach blends the certainty of a fixed‑price PPA with the market‑linked upside of a spot purchase. TUS Group currently manages over 150 GWh under flex‑management arrangements, demonstrating that disciplined portfolio construction can consistently beat supplier projections – by 20 % in the last 12 months across our 30‑plus supplier panel.

How a multipurchase contract is built

Period choices – monthly, quarterly, seasonal

The first decision is the granularity of the purchase periods. Most UK businesses find quarterly periods a pragmatic balance:

Monthly – offers the highest precision but increases administrative overhead and may lock you into price points that are already moving.
Quarterly – aligns with most corporate budgeting cycles and matches the typical reporting cadence of Ofgem’s Market‑wide Half‑Hourly Settlement (MHHS).
Seasonal – useful for firms with strong demand seasonality (e.g., food‑processing) and reduces the number of price points you need to monitor.

Tranches, caps and triggers

A tranche is a block of volume (e.g., 0.5 GWh) purchased at a specific price band. Tranches are stacked to cover the full forecast demand. Two safety mechanisms are built in:

Caps – a maximum price you will ever pay for a tranche. If the market price exceeds the cap, the tranche is settled at the cap level.
Triggers – a market price threshold that, when breached, automatically moves the remaining unfixed volume into the next cheaper tranche or into a spot‑market bucket.

For example, a contract might contain:

Tranche	Volume (GWh)	Price band (£/MWh)	Cap (£/MWh)
1	0.8	45‑55	55
2	0.7	55‑65	65
3	0.5	65‑80	80

If the market price spikes to £90/MWh, the trigger moves the remaining 0.5 GWh into the third tranche, capping exposure at £80/MWh.

When to fix non‑commodity components

Non‑commodity costs – capacity (TNUoS), distribution (DUoS), reactive power (RO) and balancing services – are less volatile than the wholesale commodity price but still subject to regulatory changes. The optimal time to lock these in is before the annual REGO (Renewable Energy Guarantees of Origin) price review and ahead of the annual Ofgem network tariff consultation (usually published in Q2). By fixing these components early, you capture the 27 % average switching saving that TUS’s free Yolk portal reports for its clients.

Worked example – a 3 GWh portfolio

Below is a realistic scenario for a manufacturing firm with an annual demand of 3 GWh, split evenly across the year.

Assumptions

Forecast demand: 3 GWh (250 MWh per month)
Market price forecast (based on the latest Ofgem Electricity Market Report): £48/MWh average, with a 30 % volatility band.
Non‑commodity costs (average 2025 rates): TNUoS £12/MWh, DUoS £6/MWh, RO £2/MWh.
Desired cap on commodity exposure: £70/MWh.
Contract length: 12 months, quarterly periods.

Contract structure

Quarter	Tranche volume (GWh)	Price band (£/MWh)	Cap (£/MWh)
Q1	0.6	45‑55	55
Q2	0.6	55‑65	65
Q3	0.6	65‑75	75
Q4	0.6	75‑85	85

The trigger is set at £70/MWh. If the market price exceeds this level in any quarter, the remaining volume for that quarter rolls into the next higher tranche, but never beyond the cap.

Cost calculation (illustrative)

Assume the following realised market prices:

Q1: £50/MWh – falls within tranche 1, so the firm pays the mid‑point £50/MWh.
Q2: £68/MWh – sits in tranche 2, pay £60/MWh (mid‑point).
Q3: £78/MWh – exceeds the trigger (£70), so the 0.6 GWh moves to tranche 4 and is capped at £85/MWh. The firm pays £85/MWh for Q3.
Q4: £55/MWh – falls back into tranche 1, pay £50/MWh.

Commodity cost = (0.6×£50) + (0.6×£60) + (0.6×£85) + (0.6×£50) = £30 + £36 + £51 + £30 = £147 k.

Non‑commodity cost = 3 GWh × (£12+£6+£2) = 3 GWh × £20 = £60 k.

Total annual cost = £207 k, i.e. £69/MWh average.

For comparison, a pure spot purchase at the same realised prices would have cost: (0.6×£50)+(0.6×£68)+(0.6×£78)+(0.6×£55)=£30+£40.8+£46.8+£33 = £150.6 k commodity, plus the same £60 k non‑commodity = £210.6 k. The multipurchase contract saved £3.6 k (≈1.7 %) while delivering price certainty for three of the four quarters.

Risk‑adjusted perspective

If the Q3 spike had been £95/MWh, the cap of £85 would have limited exposure, delivering a saving of £10 k versus spot. Over a 12‑month horizon, the expected saving from the cap‑trigger structure aligns with TUS’s track record of delivering 5‑15 % optimisation savings and a 2‑3 year payback on voltage‑optimisation projects – a useful benchmark when presenting the business case to the board.

Managing the contract with TUS

TUS’s flex‑management platform continuously monitors market prices against the contract triggers. With a portfolio of over 150 GWh under active management, the firm can benefit from automated re‑balancing that has historically beaten supplier forecasts by 20 %. The Yolk portal also provides a transparent view of realised costs versus the contracted bands, supporting SECR reporting and the finance team’s cost‑allocation models.

Bottom line

Multipurchase contracts give UK mid‑size businesses a pragmatic middle ground between full fixed‑price PPAs and volatile spot purchases. By selecting appropriate period granularity, layering tranches with sensible caps, and fixing non‑commodity components ahead of regulatory price reviews, you can lock in cost certainty while still capturing upside when the market softens. A realistic 3 GWh example shows a modest but measurable saving and a clear risk‑mitigation pathway – a compelling proposition for any finance director tasked with delivering predictable energy spend under the SECR and CCL regimes.