2x 3090 do almost $20/ day, but system draws 750w-800w from the wall. Dont know how to calculate cost of power per day.
Did you set it up properly? Are the GPU clocks optimized or its just stock?
A 2x3090+rest system should draw maybe less than 400W or around that.
800W = 0.8KW x 1h = 0.8KWh x24h = 19.2KWh/Day
How much is your cost per KWh?
My power provider has a charge of 0.0639€ per KWh. I have to add on that the power grid charges (distribution/maintenance), and VAT at the end.
Roughly the total cost is around 0.13~0.14€ per KWh.
So if I had a system of 800W my cost would be 2.5~2.6€ per day.
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Right now I have a 3900G system with x5 RX580s and my DD system with 1 5700XT. The total hashrate is 200~210MH/s and the power from wall for both is 900W (680 + 220).
Gross profit is a little more than 10€ per day. Power cost is around 3€, so the real profit is ~7€.
For me it doesn't really matter if the profit is 7€ or 4€ or 10€ per day. What matters is on what price I will sell ETH the next 10y.
For those who want to sell right away yes it matters the current ETH price and what a mining system can mine. For me not at all...
I was mining 3y ago when the mined ETH and power cost was almost equal. I didn't sell it back then. What I mined back then, now is worth more than x10.
So the comments about how mining is profitable today or not are more or less irrelevant. It depends on what you wish to do with it and what price would come the next years.