The blocked account is the mechanism by which Germany satisfies itself that you can support yourself for a year. You deposit an amount covering living costs with an approved provider, and it is released to you in monthly instalments after you arrive.
It is frequently misunderstood as a fee. It is not. It is your money, and you spend it while living in Germany. What it does require is liquidity at a specific moment, months before you would otherwise need it.
Timing is the whole problem
The account must be opened, funded, and confirmed before the visa appointment. Appointment slots at German missions are limited and are booked well in advance, which means the money has to be ready earlier than most families plan for.
Students who wait for an admission offer before starting the account routinely discover they cannot make the appointment in time. That is a purely procedural loss and it costs an intake.
Source of funds
The money must be documentable. A transfer from a family member is fine where the relationship and the sponsor's own finances are evidenced; an unexplained lump sum is not.
Providers vary in fees, transfer methods, and how quickly they confirm. Choose one that is recognised by the mission you will attend and factor its processing time into the plan.
Alternatives and interactions
In some cases a formal declaration of commitment by a sponsor resident in Germany can substitute, and scholarship holders may be exempt in whole or part. These are specific circumstances, not general options.
The blocked account is also only one strand of a German application. It runs in parallel with APS certification and university applications, and applications that run these three in sequence rather than in parallel usually miss the intake.