Procurement

A practical deep dive into multipurchase contracts for UK businesses

Multipurchase contracts let organisations with 1‑5 GWh of annual demand lock in part of their electricity spend while retaining flexibility. This article explains the mechanics – period selection, tranches, caps and triggers – and shows when to fix non‑commodity components. A worked example using realistic UK pricing illustrates how to achieve cost certainty and avoid over‑paying the market.

By TUS Trade Desk — Commercial Energy Consultants•Published 8 October 2026•6 min read

Multipurchase contracts are a hybrid between a fixed‑price supply agreement and a pure market purchase. For a UK business with a modest 1‑5 GWh portfolio they provide a way to secure a predictable portion of the bill while still benefiting from lower spot prices when the market softens. The core thesis is simple: use the contract to cap exposure on the volume you can predict, and let the remaining demand float.

How a multipurchase contract is structured

A multipurchase (or "multi‑tranche") agreement is built around three inter‑related elements – the time‑period, the tranche volume and the price‑cap/trigger mechanism. Each element can be tailored to the consumption pattern of the site, the risk appetite of the finance director and the procurement strategy of the operations leader.

Period choices

Monthly – best for sites with relatively stable daily demand (e.g. data centres, manufacturing lines). The contract is settled each calendar month, allowing the supplier to invoice against the actual metered volume.
Quarterly – suits businesses with seasonal peaks that smooth out over three‑month blocks, such as retail or hospitality.
Seasonal – aligns with the traditional UK electricity season (Winter: Oct‑Mar, Summer: Apr‑Sep). This is useful when the portfolio is heavily weighted towards heating or cooling loads.

The period you select determines the granularity of the volume commitment and the frequency of price adjustments.

Tranches, caps and triggers

A tranche is a pre‑agreed volume of electricity purchased at a negotiated price. The contract can contain several tranches, each with its own cap and trigger:

Cap – the maximum price the buyer will pay for the tranche volume. If the market price exceeds the cap, the supplier absorbs the excess.
Trigger – the price level at which the contract automatically moves the tranche into a “price‑review” mode, often resetting the cap to a new market‑linked level.

Typical settings for UK multipurchase contracts are:

Cap: 5‑15 % above the agreed fixed price.
Trigger: 10‑20 % above the fixed price.

These ranges align with the historical volatility of the UK wholesale market and deliver a 2‑3 year payback on optimisation measures, as demonstrated by TUS’s voltage optimisation projects.

When to fix non‑commodity components

Non‑commodity components – network charges (TNUoS, DUoS), environmental levies (CCL, REGO) and capacity market payments – are regulated and change infrequently. Fixing them in the contract provides two benefits:

Budget certainty – the total bill can be modelled without waiting for quarterly Ofgem price reviews.
Negotiation leverage – TUS’s 30+ supplier panel enables us to benchmark network charge components and lock in the most competitive rates.

The rule of thumb is to fix non‑commodity components when the expected annual change is under 2 % (the typical inflation‑adjusted movement in the Capacity Market). For larger expected shifts, it may be cheaper to keep them variable and absorb the change in the commodity price.

Worked example – a 2 GWh annual portfolio

Assumptions

Annual demand: 2 GWh (≈5.5 MWh per day)
Period: Monthly
Fixed commodity price: £45 /MWh (negotiated with a Tier‑1 supplier from TUS’s 30+ panel)
Spot market reference: £60 /MWh (average Q4 2023 price)
Cap: 10 % above fixed (£49.5 /MWh)
Trigger: 15 % above fixed (£51.75 /MWh)
Non‑commodity charges (fixed): £12 /MWh (incl. TNUoS, DUoS, CCL, REGO)
Expected spot volatility: ±£10 /MWh

Step 1 – Allocate tranche volume We commit 60 % of the monthly forecast (≈3.3 MWh) to the multipurchase tranche. The remaining 40 % (≈2.2 MWh) stays on the spot market.

Step 2 – Calculate monthly cost

Component	Tranche volume	Price	Cost
Fixed commodity	3.3 MWh	£45	£148.5
Fixed non‑commodity	3.3 MWh	£12	£39.6
Spot commodity (remaining)	2.2 MWh	£60	£132
Spot non‑commodity	2.2 MWh	£12	£26.4
Total monthly bill	–	–	£346.5

Step 3 – Apply cap and trigger If the spot price spikes to £70 /MWh, the tranche price is capped at £49.5 /MWh. The cost for the tranche rises to £163.4, still well below the spot cost (£140 for the remaining volume). The trigger at £51.75 /MWh would prompt a renegotiation for the next quarter, but the cap protects the buyer in the interim.

Step 4 – Annual saving Without a multipurchase contract the entire 5.5 MWh/day would be bought at the spot average (£60 /MWh), costing £330 k per year. With the contract the projected annual cost is £285 k – a 13.6 % saving, equivalent to £45 k per year. This mirrors the 27 % average switching saving reported by TUS’s Yolk portal, albeit on a smaller scale.

Managing risk and performance

Volume monitoring – Use TUS’s free Yolk portal to track actual consumption against the committed tranche. Deviations above 5 % trigger a review.
Supplier performance – TUS’s 150+ GWh under flex management gives us the data to benchmark supplier delivery against market indices.
Regulatory alignment – Ensure the contract respects Ofgem’s Minimum Household Energy Standards (MHHS) for demand‑side response and the SECR reporting requirements for large undertakings.
Renewal strategy – Review caps and triggers every 12 months. The market has beaten supplier projections by 20 % in the last 12 months, so a tighter cap may be justified.

Bottom line

Multipurchase contracts give UK businesses with 1‑5 GWh portfolios a pragmatic middle ground between full price certainty and market exposure. By selecting the appropriate period, allocating a realistic tranche, and fixing non‑commodity components, finance directors can lock in 5‑15 % savings with a payback horizon of two to three years. The worked example shows how a modest 60 % tranche can deliver double‑digit savings while preserving the upside of a falling spot market. Leveraging TUS’s extensive supplier panel and data‑driven optimisation ensures the contract remains competitive throughout its term.

FAQs

What happens if my actual consumption exceeds the tranche volume? The excess is settled at the prevailing spot price, subject to the same non‑commodity charges as the tranche.
Can I add or remove tranches mid‑contract? Most suppliers allow a limited number of adjustments (usually one per year) provided a minimum notice period of 30 days is observed.
How do caps and triggers affect my carbon reporting? Caps and triggers are financial mechanisms only; the underlying electricity source remains the same, so SECR and carbon accounting are unchanged.