In a very short amount of time essentially all mining will be on ASICs. The BFL Jalapeno just shipped. That generation of ASIC will probably represent the majority of hashing when all backorders are shipped.
That device does 5.5 Ghash/s and consumes 30W, per David Perry's first hand account of the one he received.
Today the hashing capacity is 66 Thash/s. That is 66,000 Ghash/s. If all of that was done on BFL Jalapenos there would need to be 12,000 of them. Each consumes 30W so all 12K of them draws 360kW. So in one day that electrical consumption is 8,640 kWh. At $0.15 per kWh (the average residential price of electricity in the U.S.), that totals $1,296 per-day.
The Avalon ASIC is about half as efficient (60 Ghash/s consumes 600W), so if all mining today was Avalon ASICs, then that total electrical consumption is about $2,376 per-day.
Maybe close to a third of the network is still GPU (e.g., 22Thash/s), so perhaps that would be about $35K USD per-day, but those GPUs will quickly be dropping offline as their profitability drops thanks to ASICs.
This doesn't help know what total electrical consumption a year out will be but that is because it isn't known today what the exchange rate will be a year out.
Also, today's ASICs are first generation. They could get replaced with new designs that perform 50% better even.