13. Fund Your Wallet

Before deploying your program, you need devnet SOL to pay for the on-chain storage (called "rent").

You may already have some

If you came through Course 1 you funded this same wallet there, and it is very likely still holding SOL — devnet balances do not expire, and nothing in Courses 2 or 3 spent any. So check the balance in the widget below before you airdrop: if you are already at 4-5 SOL, you are done and the next lesson is waiting.

If Course 3 is your entry point, or the balance has drained, read on.

How Much SOL Do You Need?

Deploying an Anchor program requires approximately 2 SOL on devnet:

• ~1.63 SOL for the buffer account (temporary storage during upload)
• ~1.63 SOL for the programdata account, which holds your bytecode for the life of the program
• ~0.00114 SOL for the program account itself (it is only 36 bytes — a pointer, not the code)
• ~0.3 SOL for transaction fees (200+ transactions)

Those figures are for a compiled Anchor program of roughly 229 KB, which is what your vault actually comes out to. Most of that size is the framework's account-validation and error machinery, so it barely moves with the number of instructions you wrote — three instructions and thirty cost close to the same.

Read that list again, because the two big numbers do not both stay spent. The buffer's deposit is refunded automatically: the deploy instruction drains the buffer back to your wallet in the same instruction that funds programdata. So you need ~2 SOL on hand to deploy, but you end up down roughly 1.63 SOL plus fees — and that 1.63 stays locked as long as the program exists. Getting it back means solana program close, which permanently retires the program id.

The Devnet Faucet

Solana provides a free faucet on devnet. The web faucet at faucet.solana.com is the reliable path — airdrops through the public RPC (solana airdrop) are throttled more aggressively. The web faucet is rate-limited by request frequency (a maximum of 2 requests every 8 hours, as of mid-2026); signing in with GitHub raises that limit.

Use the widget below to fund your wallet. You'll need at least 4-5 SOL to comfortably deploy — because of the request-frequency limit, that may take more than one faucet visit, which is expected, not a failure.

Tip: The faucet can be slow during peak hours. If you see "faucet is busy," just wait 30-60 seconds and try again. This is normal — devnet is a shared resource.

The same rent, at a different scale

This is the rent-exempt deposit you already sized for the vault account in module 2 — (128 + space) × 3480 × 2 — applied to something four thousand times larger. Nothing about the rule changed; only space did.

Run it on the deploy accounts and the numbers above fall out:

programdata: (128 + 45 + 234,040) × 6,960  =  1,630,122,480 lamports  ≈  1.63 SOL
program:     (128 +          36) × 6,960  =      1,141,440 lamports  ≈  0.00114 SOL

The 45 and the 36 are the loader's own metadata headers, and 234,040 is your compiled .so in bytes. Note which account is expensive: the program account is a 36-byte pointer, and the bytecode lives in programdata.

One correction worth carrying forward from module 2: rent is a deposit, not a meter, and the buffer's deposit comes back to you automatically as part of deploying. The programdata deposit does not — that one is the real price of having a program on-chain.