Not even close. According to http://realtimebitcoin.info/ about 5 MW are used for Bitcoin. According to http://en.wikipedia.org/wiki/Cost_of_electricity_by_source that would cost somewhere between 250 and 1000 USD per hour. So at most it's about 8.7 million USD (or 0.7% of the total market price of all bitcoins) per year. That's not much at all to support a functioning currency (whose true macroeconomic value is in enabling the exchange of goods and services, not the market price).
An interesting aspect of Bitcoin is that the amount of computation it requires is designed to scale up with the amount of available computation power, independant of the amount of transactions. Miners cannot increase the rate at which new bitcoins are "mined" - geting more computation power only increases their share. Thus it makes no sense to spend more money on the hardware and electricity for mining than the (basically fixed) rate of newly mined coins are worth.
An interesting aspect of Bitcoin is that the amount of computation it requires is designed to scale up with the amount of available computation power, independant of the amount of transactions. Miners cannot increase the rate at which new bitcoins are "mined" - geting more computation power only increases their share. Thus it makes no sense to spend more money on the hardware and electricity for mining than the (basically fixed) rate of newly mined coins are worth.