Tuesday, 21 May 2019

Lightning debunked - a detailed calculation that shows why Lightning is still insanely expensive

I like trying out new things. I think it's important to be familiar with different technologies so that I can form my own opinion. Let's look at Lightning.

A common argument against high fees is that Lightning transactions are so much cheaper. Here's a typical use-case: Every other week I'm meeting with a few Crypto-friends for food/drinks. I'm usually the one who pays with card and they pay me via BCH.

BTC would be too expensive for those transactions. At a fee of $4 per transaction (according to https://bitcoinfees.info/) with 4 people who pay me that would be a total >$20 in fees per evening (4 input transactions and my output transaction with 4 inputs)!

With Lightning payment channels I can only receive capacity that I sent first. I can't open a new channel and directly receive coins. However, some providers such as Bitrefill sell "prefilled" channels that are directly able to receive coins. Let's try to buy a channel at https://www.bitrefill.com/buy/lightning-channel/ which is kept open for a guaranteed 30 days (so I'd need to buy one channel per month). In average everyone spends $50 per night so that would be $200 total per night - let's say around $400 per month. Sometimes nights are more expensive (we don't always eat/drink at the same place). While the average is $400, the max. I'd need to be able to receive is around $600 per month.

$600 is 7,569,000 Satoshis which means the 8,000,000 channel by Bitrefill is a perfect choice. Even if I would have calculated with only $400 per month I still would have had to buy the same channel as the next smaller channel with 4,000,000 Satoshis would have been to small for $400 per month. That 8,000,000 channel costs me 0.00242400 BTC in fees (to Bitrefill) which is $20 at current prices. If I add my own transaction fees that I need to pay in order to send those fees to Bitrefill that's a total of $24 per month or $12 per evening.

That's a fucking 4% in the best case (actually using the channel's full capacity) and an insane 6% in fees in the average case where I only spend $400 per month. If I would buy a Square Reader and charge my friends' credits cards that would only cost me 2.75% in fees - and they would get back 2% in cashback on average!

Now I can already hear the response some might post: "That's just the total capacity of a Lightning channel, but you can re-use it as often as you want to (within those 30 days) as you can send money to someone via Lightning to re-fill that balance.". Well, turns out I don't have anyone to whom I want to send money via Lightning. The same is true for shops that accept Lightning: While they need to buy expensive payment channels to accept payments, they're probably not going to spend any of those coins with Lightning. As a consequence they either need to charge higher fees to users, or hide those processing fees in the prices of their items.

So let's take a step back and tell me again: How exactly is Lightning going to help me against the high fees?

submitted by /u/otk16
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source https://www.reddit.com/r/btc/comments/br7oqp/lightning_debunked_a_detailed_calculation_that/

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