Flex vs Fixed vs Multipurchase — which UK business energy structure wins?
Three structures, three risk profiles, three operational footprints. This table compares them across the criteria that actually matter, and the decision framework below walks you through which one fits your portfolio.
Side by side
The same 12 criteria every UK business energy buyer asks about. Use the rows to spot the ones that actually matter for your business.
| Criterion | Fixed | Multipurchase | Flex Portfolio |
|---|---|---|---|
| Best for portfolio size | Under 1 GWh/year | 1–5 GWh/year | 5 GWh+/year |
| Number of suppliers signed with | One | One | One (framework) |
| Price set on… | One day at signature | Multiple tranches in-term | Continuous, in tranches |
| Captures market dips | ✗ | ✓ | ✓ |
| Protected from spikes | Yes (single price) | Yes (cap and trigger) | Yes (cap and trigger) |
| Non-commodity components — choose what to fix vs pass through | ✗ | ✓ | ✓ |
| D-5 default trade (never out of market) | ○ | ✓ | ✓ |
| Trade desk reporting after every trade | No trades to report | ✓ | ✓ |
| Take-or-pay clause | Usually present | Negotiable | Usually removed |
| Operational input required from you | Almost none | Light, quarterly | Light, regular |
| Best when wholesale is rising | Lock early helps | Forward tranches help | Forward tranches help |
| Best when wholesale is falling | Locked at higher rate | Capture dips in tranches | Capture dips actively |
Six steps to the right structure for your portfolio
- 1
Confirm portfolio size
Pull your last 12 months of total kWh consumption (electricity, and separately gas). Under 1 GWh, flex rarely makes sense on its own — competitive fix usually wins. 1–5 GWh, Multipurchase becomes the default. 5 GWh+, full Flex Portfolio is usually the best fit.
- 2
Sense-check your risk appetite
If your finance director cannot tolerate a budget surprise, that pushes toward fixed or Multipurchase with a tight cap. If you can absorb in-period variance for the chance to capture market dips, that pushes toward full Flex.
- 3
Look at the forward curve
Check whether the UK forward gas and power curves are in contango (rising) or backwardation (falling) for your delivery years. Rising curves favour locking ahead in forward tranches; falling curves favour deferring tranches via Multipurchase or full Flex.
- 4
Decide what to do with non-commodity components
On Multipurchase or Flex, choose per component (DUoS, TNUoS, RO, CfD, FiT, CCL, E11) whether to fix or pass through. Generally: fix the components that are steadily rising; pass through the volatile ones.
- 5
Set cap, trigger and tranches
For Multipurchase or Flex, agree your budget cap, your trigger level under it, and how many tranches per period (up to four). These rules govern when the trade desk acts on your behalf.
- 6
Sign the framework, run the in-life
On Fixed, the supplier contract is your in-life agreement. On Multipurchase or Flex, you sign the framework and then trade tranches against it through the term. Every trade comes with a written rationale and a Purchase Management Schedule.
Move from a single price-fix to a portfolio you actively manage.
Our trade desk currently manages over 150 GWh in flex contracts on behalf of UK businesses, and beat supplier projections by 20% in the last 12 months. You stay in control. We do the trading.
Fixed wins when…
- You consume under 1 GWh / year
- You cannot give any operational time to the energy book
- The forward curve looks unfavourable for the next 12 months and you'd rather lock
- Budget certainty matters more than capturing dips
Multipurchase wins when…
- You consume 1–5 GWh / year
- You want the discipline of flex without setting up a framework agreement
- You can spare ~2 hours per quarter to review trades
- Your finance team wants both budget certainty and upside capture
Flex Portfolio wins when…
- You consume 5+ GWh / year
- You want granular control of every non-commodity component
- You're planning on-site generation (solar, battery, CHP) and need take-or-pay removed
- Energy is a material cost and worth the framework agreement effort
Flex vs Fixed vs Multipurchase — quick questions
Want this comparison run against your actual portfolio?
Send your last 12 months of consumption and your current contract terms. We'll model fixed, multipurchase and full flex against your specific portfolio and put a written recommendation in front of you — for free.