Greetings,
Does anyone know a relative hash-rate value needed for GPUs to successfully mine Bitcoin or its alternatives these days?
Assume that the electricity price is relatively low - around 3-5 cents per kW.
You can't mine Bitcoin with GPU's. Those days were over in 2013.
Current Bitcoin ASIC Mining hardware starts out 8 to 13 THs per machine. So that would probably be the minimum hash rate you would want to start with.
Good Luck with your low electric price.