Ethereum lowest price based on miners viewpoint

Today i want to calculate ETH death window based on fundamental analysis!
what's the meaning of death window ? i called lowest price and lowest time period after that all of Ethereum network crash and dead for better meaning i want to clear after this price mining is not profitable and all the miner switch off the machine .

lets do that:

all of us know ETH network generate new block after 14.5 seconds and today block rewards is approximately near 3 Eth.
i would like to estimate how much miner pay for electricity to generate a single Ethereum for this purpose we need to chose sample and formal miner devices and total network hashrate .

base on my experience from mining optimum mining rig with 6 GPU ( optimum GPU card ) cards are able to generate 180 MH with using 1.2 Kwh electricity,
the national average electricity rate is 0.1189 $/Kwh .

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how many mining rig we need to build today Ethereum networks ?
total Ethereum network speed is 287,486.80 GH/s ( refer to etherscan.io) so we need 287486800 MH/s / 180 MH/s = 1,597,149 mining rigs
this bunch of devices is using 1,916,579 Kwh,
during an hour Ethereum network generate near 757 ETH
today a single ETH cost = total eth network electricity * electricity cost / total ETH during an hour = 301 $
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