Hello Johano.
The answer to this question could be estimated by looking at the reward given to miners.
Bitcoin miners are mostly professional miners that need to make a profit. It's a risky business that requires an important investment and you need to spend lot of time configuring and securing your mining farm. So you definitely want a good cut. Bitcoin is giving about 5 million a day to miners. I think more than half is spent in electricity. Some say it's rather 90% though. If 2.5million$ are spent daily in electricity (so 50%), it better be the cheapest possible. That's why miners go to China or India where the price is 0.08$/kWh. So my guess would be that bitcoin network uses 31.25 millions of kWh a day. To give you an idea, recent statistics showed that an American home uses 900kWh a month.