Fee Efficiency for Multisig

To understand why P2WSH is the modern standard, we must look at the mathematical difference in how different multisig types are taxed by the network. We will compare a standard 2-of-3 Multisig spend.

1. Legacy P2SH (The Baseline)

In legacy P2SH, the entire input (Signatures + Script) is considered "Base Data."

• Estimated Virtual Size: 297 vBytes

• This is expensive because every byte costs 4 Weight Units.

2. Nested SegWit (P2SH-P2WSH)

In Nested SegWit, the keys and signatures move to the Witness, but the 34-byte wrapper stays in the ScriptSig.

• Estimated Virtual Size: 175 vBytes

• Savings: ~40% vs. Legacy.

3. Native SegWit (P2WSH)

In Native SegWit, the ScriptSig is removed entirely. The transaction header and output are the only "Base Data" remaining.

• Estimated Virtual Size: 139 vBytes

• Savings: ~53% vs. Legacy.

4. The Scaling Comparison Table

If the network is congested and fees are 100 sats/vByte:

Multisig Type	vSize	Total Fee (Sats)	Efficiency Rank
Legacy (3...)	297 vB	29,700	Poor
Nested (3...)	175 vB	17,500	Good
Native (bc1q)	139 vB	13,900	Best

5. Why do "3" addresses still exist?

If Native SegWit is 50% cheaper, why does anyone use P2SH-P2WSH? The only reason is Backward Compatibility. Many old exchanges and legacy businesses still cannot send to bc1q addresses. However, for internal transfers and modern payment flows, P2WSH is the undisputed king of efficiency.

In the final section, we will build a Python P2WSH Auditor.