A two-part tariff charges a fixed fee for access plus a variable fee for consumption. The buyer pays once to get in and again for what they use, and the two components answer different questions.

The fixed fee captures the value of availability and covers the cost of standing ready to serve. The variable fee scales with consumption and tracks value in use. Splitting them lets a seller serve light and heavy users off one structure without pricing either out, which a single per-unit rate cannot do. The trade sits in the ratio: weight the fixed side and revenue becomes predictable while small buyers balk; weight the variable side and adoption is easy while forecasting gets harder.

Manufacturing and services have run this for decades under other names, which is why it belongs in the vocabulary rather than in a SaaS glossary. Equipment plus consumables, minimum retainer plus hourly, connection charge plus usage. Software rediscovered it as a platform fee plus consumption and called it hybrid, but the mechanism is the same and so are the failure modes.

The fixed component is where B2B negotiations concentrate, because it appears on the contract as a committed number while consumption is a forecast. Procurement attacks what it can see. Give ground there and the structure inverts, leaving the variable fee carrying a load it was never sized for, and the price realization damage compounds with volume rather than showing up once.

A two-part tariff works when both components are defensible on their own terms. When the fixed fee is only there to hit a revenue number, buyers find that out fast. Reach out to Acustrategy to set the split where both halves earn their place.