Block-and-Index vs. Fixed Commercial Energy

Identify whether the fixed portion is volume or percentage

Ask whether the contract fixes a MW block during specified hours, a percentage of shaped load or another defined quantity. A fixed MW block translates to different energy quantities when the covered hours change. A percentage load-following layer can behave differently as consumption rises or falls. The written confirmation must identify exactly what was purchased.

Determine how residual use and surplus blocks are settled. If actual load falls below a fixed block, the treatment of excess energy can create exposure even though the buyer intended to reduce risk. Check the index location, settlement interval, loss treatment, fees and rights to add layers before comparing the product with a fixed offer.

The fixed alternative has its own boundaries

A supplier’s fixed requirements price can transfer specified market and shaping risks for an agreed account profile, but it may include tolerance or other conditions. Review the components actually fixed and the consequences of a major load change. Calling the alternative fixed does not eliminate the need to examine quantity and settlement language.

Block-and-index may give an experienced purchasing team more control over how and when portions are fixed. That flexibility comes with ongoing decisions and invoice oversight. Someone needs to track purchased coverage against current load, not simply approve the first transaction and assume the account is protected for the whole term.

Hypothetical mixed-price calculation

Imagine 100,000 kWh in a simplified period, with 60,000 fixed at $0.08 per kWh and 40,000 settling at a hypothetical $0.11. Modeled energy cost is $4,800 plus $4,400, or $9,200. A fully fixed $0.09 case costs $9,000 for the same usage and included scope.

If the residual rate instead equals an invented $0.06, the mixed case costs $7,200. These are arithmetic scenarios, not product quotes or evidence of likely savings. Real hourly blocks, shape mismatch, surplus settlements and separate capacity or network charges can create results that a single-period weighted average does not capture.

Choose a governance process before choosing layers

Define who can approve purchases, how open volume is monitored, how forecasts are updated and what budget exposure requires action. Keep trade confirmations or supplier layer records with the base agreement. If those responsibilities are unclear, the product can be administratively unsuitable even when the initial modeled price looks attractive.

Request a worked settlement on representative interval data and a stress case for a shutdown or expansion. Then compare that result with the fixed offer’s tolerance and exclusions. The useful decision is whether the business can manage the specific residual risks, not whether a hybrid label sounds more sophisticated. No allocation or purchasing sequence is recommended by this educational example.

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