I agree with goatlips, if you have a lot of smelting to do, you need a heat source like propane, natural gas, or even gasoline (I've used them all).
However, for the guy that has a five gallon bucket of wheelweights to do, electricity will do the job. A 750 watt hotplate is only good for small batches of 5 pounds or so. If you're willing to do some work, you can rig up a bigger heating element. I recently cobbled one together using a 3000 watt heating element from an electric range. This element cost me $1, and the support structure is a discarded coffee can. I wired it into a 20 amp, 240 volt circuit in my shop. It melted a couple of 35 pound lead counterweights in less than an hour. As far as the cost of the electricity, in my area it costs 10 cents per KWH. That means I used 30 cents worth of electricity to melt 70 pounds of lead.