Variable	Symbol	Value	Unit	Source
Network Hashrate	HN	296000	GH/s	https://etherscan.io/chart/hashrate
GPU Hashrate	HM	31.2	MH/s	https://www.legitreviews.com/geforce-gtx-1070-ethereum-mining-small-tweaks-great-hashrate-low-power_195451
GPU Power	PM	110.6	W	https://www.reddit.com/r/ethereum/comments/7vewys/10000_tons_co2_per_day_and_climbing_eip_858/dtrswyz/

Network Power Consumption (P_N)

A baseline value for network power consumption can be found by multiplying the total network hashrate with a “best case” value for the power/hashrate ratio that a miner can achieve.

P_N = H_N x P_M / H_M

P_N = 296000 (GH/s) x 110.6 (W) x 1000 (MH/GH) / ( 31.2 (MH/s) x 10^6 (W/MW) )

P_N = 1049 MW

As a side note, people often confuse power (W) and energy (power x time, eg. Wh). For instance, assuming an average daily P_Nd of 1049 MW we can calculate that days Energy consumption by multiplying by the number of hours in a day.

E_Nd = P_Nd x T_d

E_Nd = 1049 (MW) x 24 (h/d) / 1000 (GW/MW)

E_Nd = 19.7 GWh