How do AI credits work? Price, tokens and expiry

AI credits are a prepaid currency: you buy them from a vendor at a set price, and each generation spends a number of them that depends on the model, the length and the resolution. To know what a credit is worth, you need two numbers from the vendor's pricing page: the dollar price of one credit and how many credits the model you use spends per second or per image.

The examples come from Runway's API pricing and plans pages, read 2026-09-28, and from Sume's Usage and Video generation docs and its pricing code.

What is one AI credit worth?

It depends on how you bought it. Runway's developer API sells credits at $0.01 each, so Gen-4.5 at 12 credits a second costs $0.12 a second. A plan's credits cost the plan price divided by the allowance: Runway Standard billed annually is $12 a month for 625 credits, about $0.0192 a credit if you count only the credits, and the plan's own conversion says 625 credits buy 52 seconds of Gen-4.5.

What billing units will I see?

Credits are only one way to meter AI video. The same generation can be priced in credits, tokens, seconds or jobs, depending on the vendor and the model.

Credits vs tokens: what's the difference?

A token measures work; a credit is money. Text models count tokens as chunks of text. Video tokens can count pixels and frames instead: Sume's pricing code counts a Seedance clip as width × height × seconds × 24 ÷ 1,024 video tokens and bills dollars per 1,000 of them. A credit sits one layer above: it is the vendor's own currency, and its rate card says how many credits a second, an image or a token costs.

When do AI credits expire?

Each vendor sets its own rules, so read the pricing page before you buy in bulk. Runway's monthly credits on Standard and Pro don't roll over and reset within 24 hours of the billing date, Max rolls over up to one month of unused credits, and additional credits bought on top of a plan never expire.

On Sume, in current code, a purchased top-up expires 365 days after it is credited, and a plan's included usage expires at the end of its billing period with no rollover. GET /v1/balance (API reference) reports the next expiry in expiration.next_expires_at, with the amount expiring then and the amount expiring within an expiring-soon window.

How do credits work on Sume?

Sume's balance is in US dollars; the older available_credits field reports it as rounded cents for compatibility. Generation, the Sume Agent, Formats and the API all draw from that one balance at each model's published rate. A job reserves its estimated cost when you submit it, captures the cost when it completes, and releases the reserve if it fails or is canceled before capture.

Top-ups are a dashboard operation: the public API reads the balance and usage but has no top-up endpoint. How Sume pricing works covers the plans and wallet, and Insufficient credits error 402 covers what happens when the balance runs out.