> And it says: "Plugging in an electric vehicle is, in some cases, the equivalent of adding three houses to the grid."<p>What? Really? It couldn't possibly be t

> And it says: "Plugging in an electric vehicle is, in some cases, the equivalent of adding three houses to the grid."<p>What? Really? It couldn't possibly be that! Anyone? I'm a former NASA electrical engineer, and I can tell you it's so. A charging electric car requires an enormous amount of energy, and a suitable charger will greatly increase household power consumption for the duration of the charging cycle. The Tesla model S has two battery types, let's use the larger battery for this example -- it has a capacity of 85 kilowatt-hours (KWh). Assuming 25% system losses, to fully charge this battery requires about 106 KWh. That translates to 8.83 kilowatts for twelve hours. 8.83 kilowatts at 240 volts requires about 36.9 amperes. A typical household's electrical system can handle this current level if it's been set up properly. Okay, so for 12 hours each night, the electric car requires 240 volts at 36.9 amperes to top off its battery. How does this compare to a normal household's power usage? Here's an online reference: http://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3 http://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3 Q: "How much electricity does an American home use?" A: "In 2011, the average annual electricity consumption for a U.S. residential utility customer was 11,280 kWh ..." An annual usage of 11,280 KWh divided by the number of days in a year gives 30.88 KWh/day. Compare this to the daily energy required by the electric car -- 106 KWh. The bottom line is that the electric car's power usage is about 3 1/2 times that of the remainder of the household, and a household with an electric car uses 4 1/2 times as much power as a household without an electric car. Returning to the original quote: > "Plugging in an electric vehicle is, in some cases, the equivalent of adding three houses to the grid." That's just about right.