How reliable is the spot price surcharge estimate, and what affects it?

The reliability of the surcharge estimate depends on several factors. Understanding these helps you interpret the result correctly and avoid drawing the wrong conclusions.

Factors that improve reliability

More months of matched invoice data (12 months covers a full seasonal cycle and averages out winter/summer variation)
High data coverage percentage — ideally above 90%
Markets with simple, transparent tariff structures such as the Nordic countries (Norway, Sweden, Finland, Denmark)
Invoices with clearly separated unit rate line items

Factors that reduce reliability

Low data coverage (invoice data or spot price data is incomplete for the period)
Complex tariff markets where regulated charges are embedded in the unit rate:
- UK: Renewables Obligation (ROC), Feed-in Tariff (FiT), Contract for Difference (CfD), capacity market charges — these appear as part of the unit rate but are not supplier margin
- Germany: Network fees, concession levy, smart meter charges may be bundled into the unit rate
- United States: Demand charges, capacity charges, and utility-specific riders vary widely by state and utility
Short data windows (1–2 months may not reflect seasonal price variation)
Invoices with all-inclusive tariffs where commodity and network charges are not itemised separately

Data coverage thresholds

90–100%: High confidence — seasonal patterns are well represented
70–89%: Moderate confidence — some gaps exist; treat with care
Below 70%: Low confidence — result should not be used for any decision-making

inbilit does not guarantee the accuracy of surcharge estimates. External spot price API failures, timezone differences, data gaps, and variations in how suppliers calculate pricing can all cause the estimate to differ from your actual supplier margin. Always verify independently.