What happens to credits you do not spend
Where generation is billed in credits, two things decide the real cost: how long credits last, and what happens when a generation fails. Three vendors publish both, and they do not agree on either. As of 2026-09-12.
| Vendor | Plan credits | Purchased credits | Failed or blocked generations |
|---|---|---|---|
| Kling | Valid one month | Valid two years | Refunded when a generation fails |
| Runway | Reset within 24 hours of the billing date | Extra purchases from 1,000 credits | Moderated generations still cost credits on the developer API |
| Vidu | Valid 30 days | Valid two years, bonus credits included | Not stated on the pricing page |
Inclusion rule. Vendors that publish credit validity on a public pricing page. A vendor stating a credit price without stating validity is not given a row. Order. Alphabetical by vendor name.
1Expiry turns a rate into a floor
Monthly plan credits that expire mean the effective rate depends on how much of the allowance is used. A production using half its monthly credits is paying twice the headline rate, and no pricing page shows that number.
Purchased credits lasting two years behave differently: they are closer to a prepayment than a subscription, and the published per-credit price is then the real one.
2Failed generations are where vendors differ most
One vendor refunds credits when a generation fails; another states that moderated generations cost the same as successful ones. For a production with a meaningful rejection rate, that difference is larger than most of the per-second gaps in the ledger.
It is also the figure least likely to appear in a comparison, because it only shows up once work is under way.
3Two multiplications, two places to be wrong
A credit rate becomes a price only after multiplying by the credit price, and the credit price often varies by pack. Publishing both halves is what makes the arithmetic possible; publishing one half is a rate that cannot be checked.
4Validity is a discount or a penalty depending on volume
Long-lived purchased credits reward buying in bulk; monthly expiry punishes uneven production schedules. A series shot in bursts pays a different effective rate from one generating steadily, on the same published price.
That difference is knowable in advance and almost never worked out, because it needs a production calendar rather than a price list.
5Bonus credits often expire differently
Where a vendor grants bonus credits with a purchase, the bonus sometimes carries the same validity and sometimes a shorter one. Where the terms distinguish them, spending order matters, and where they do not, it is worth assuming the shorter.
6Pages these figures were read from
A definition entry: what the term means, and the figures vendors put in public about it, each figure read on 2026-09-12. Related: Resolution tiers, Prompt extension.
7The production behind the price
Price aside, what goes into the seconds behind “Credit billing” is described in SceneMixer's guides:
A segment is one generation, and its length is the sum of its shots’ seconds.
SceneMixer, How to Change a Segment’s Duration, and Which Tiers Accept 30 Seconds (read 2026-10-13)
A short drama episode has two jobs: stop the scroll in its first seconds, and make the next episode feel necessary in its last.
SceneMixer, Writing Hooks and Cliffhangers Into a Short Drama Script (read 2026-10-13)