Flex vs fixed vs multipurchase — how to choose your UK business energy purchasing strategy
The simplest way to think about it: fixed is one bet on one day, multipurchase is a flexible product inside a supplier wrapper, full flex is a directly-traded portfolio. Sizing thresholds are roughly 1 GWh and 5 GWh — but risk appetite and operational reality push the line.
The three structures
Fixed-price contract
One supplier. One contract. One price, fixed for the term. The supplier bakes a hedge into the unit rate. Simple to understand, simple to budget — but you live with whatever the market happened to do on the day you signed.
Multipurchase contract
One supplier. One contract. One fixed term. But instead of fixing the price on day one, you split the volume into periods (monthly, quarterly, seasonal, annual) and tranches (up to four per period). The trade desk buys those tranches at favourable points.
Full Flex Portfolio
A framework agreement with a supplier, with TUS's trade desk operating inside it. Volume traded directly into wholesale. Triggers and caps protect your budget. Non-commodity components chosen individually to fix or pass through.
The sizing rule of thumb
- Under 1 GWh / year: usually fixed.
- 1–5 GWh / year: Multipurchase is usually the right answer.
- 5 GWh+ / year: Full Flex Portfolio becomes worth the framework setup.
The risk question
Fixed contracts are sometimes pitched as "low-risk" — but the risk is concentrated on a single decision date. Flex doesn't eliminate risk — it spreads it across time. Done well, flex captures more of the dips and less of the peaks.
Non-commodity costs: a flex/multipurchase advantage
On a fixed contract, non-commodity costs are bundled. On flex or multipurchase, you choose per component — usually fixing components that are rising steadily.
Bottom line
Don't pick a structure on instinct. The right contract depends on your volume, your risk appetite, your operational availability and the current shape of the forward curves.
Flex vs fixed vs multipurchase — how to choose your UK business energy purchasing strategy — quick questions
More articles
A practical deep dive into multipurchase contracts for UK businesses
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A practical deep dive into multipurchase contracts for UK businesses
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