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I'm not fond at all of this new way of batching tx's. This needs to revert to the old way.
But it's been like that ever since Electrum implemented "
Batch Unconfirmed Transactions" as well as "
Increase Fee (RBF)" features.
The algorithm used is based from RBF's standard which isn't changed ever since.
Your previous experiences may have been on a condition where the fee rate and sizes of the transaction is just right for it to be bumped with additional 0.2 sat/vB or close.
Like if the first transaction has a single input while the its replacement has to use additional UTXOs to cover the additional output's amount.
For example:
Let's say that you've sent a small size transaction (
1 input and 2 output) of 140 vB @ 1sat/vB = 140 satoshi absolute fee.
Then you've sent another transaction right after to batch it with that, but Electrum calculated that it has to use 6 more of your UTXO to cover the additional output's cost (
if you have lots of small UTXOs)
It'll add about 30vB for the additional output, but since the inputs are now 7, the total size would be: 580vB, the min absolute fee would be 580sat + 140sat = 720sat.
At 720 satoshi absolute fee, the batched txn's fee rate would be: 720 sat ÷ 580vB = 1.24sat/vB.
What you are saying is now what I have experienced.
I'm a high volume p2p bitcoin trade with all my trades on HodlHodl fully automated with software I built.
In the past, maybe a year ago, I could use RBF to batch a new spend with unconfirned ones. And I would simply pay 0.1 or 0.2 sat/VB more than with the unconfirmed one.
By doing this, I could cut miner fee costs by half.
In trying to cut miner fees ever more, I tried to do it all without a change address. But Electrum would not allow batching when I didn't use a change address.
But now, it has changed. It's no longer letting me increase miner fees as I wish when adding new transactions to the batch. Whatever change was made, at the wallet level, or at the Mempool level, it sucks. Because it's forcing me to pay more in fees.