This has already been answered, but I work through the problem slightly differently, which hopefully adds to its ability to be understood.
The current hash rate according to moneroblocks.info is a bit over 55M h/s, which comes out to 198 billion hashes per hour.
Let's assume the average efficiency of a minor on the network is 5 hashes / second / watt. (As a reference, a 750Ti GPU is fairly efficient, supposedly at 6 h/s/watt). Getting up from seconds to hours, that's 5 x 60 sec/min x 60 min/hr = 18,000 hashes / hour / watt. Since we're basing this off the 750 Ti specs, and they consume an average of 35 watts, then you're getting 18k h/W x 35W = 630,000 hashes / hour.
Well, in order to perform 198 billion hashes, you'd need 198B / 630K = over 314,000 CPUs and GPUs mining on the network. With 314,000 CPUs and GPUs (yes, that seems like a lot to me too), consuming an average of 35 watts (as noted above), that's a power consumption rate of just shy of 11,000kWh, or 264,000kWh/day.
Using the same electricity rate as others, at $0.15/kWh, that's $1,650/hr or almost $40k/day.