1000 gpu consume $3600 a month and earn 3 btc a day(300k satoshi per gpu)
Depends on the gpu. I started mining dogecoin in 2013, so my collection of gpu's are a mix of old and new.
The old 7950 and 7970 are still good for mining (300MHASH zcash). The 750ti too. (300khash monero). Good because the cards have already ROI'd many times.
I've sold the 6990's and 7xxx series gpu's a long time ago.. The last 9months I have expanded with NVIDIA Pascal cards only.
The 7950 architecture is 6 years old, and still going strong.. Impressive..
From wikipedia:
Radeon HD 7900
Codenamed Tahiti, the Radeon HD 7900 series was announced on December 22, 2011. Products include the Radeon 7970 GHz Edition, Radeon HD 7970 and Radeon HD 7950.
The Radeon HD 7970 features 2048 usable stream cores,[A] whereas the Radeon HD 7950 has 1792 usable stream cores, as 256 out of the 2048 cores are disabled during product
binning which detects defective areas of a chip. The cards are the first products to take advantage of AMD's new "Graphics Core Next" compute architecture. Both cards are equipped
with 3 GB GDDR5 memory and manufactured on TSMC's 28 nm process. The Tahiti GPU is also used in the Radeon HD 7870 XT, released November 19, 2012. In this case one quarter
of the stream processors are disabled, giving 1536 usable cores. Additionally, the memory interface is downgraded from 384-bit to 256-bit, along with a memory size reduction from 3
GB to 2 GB.