Dippin' in a Tesla is an expensive proposition, as we're sure you're well aware, but the US Department of Energy seems certain the cost of electric vehicles -- or at least their all-important rechargeable batteries -- will come down to reasonable levels. The government estimates a stack of cells good for 100 miles will drop to $10,000 by the end of 2015, and that 40-mile batteries for PHEVs will sink to $4,000 in the same timeframe -- both around one-third of what the containers presently cost. On the physical front, portly packages of Li-ion presently weigh 333kg (about 734 pounds) per 100 miles of range, but are expected to slim down to 222kg (489 pounds) by 2015, and shed weight precipitously in following years. Like any weather forecast, the figures are subject to the prevailing wind, but it's looking like average Americans may one day have use for all those free charging stations. Find the full report at our source link.