PG&E has a great online utility that will show you your hour-by-hour electrical consumption, directly from your smart meter. The image below is a screenshot of the first full charge of my leaf, done around 4am after driving to work and back the day before.
It takes about a day before your graph will show up online. Once it is available, you can navigate to any day in the past just by selecting the date you want from the drop-down control. I don't know how far back PG&E keeps this information for you; it appears that we have hourly data stretching all the way back to when our meter was installed a couple of years ago.
The graph shows electrical consumption in kW/hr with blue bars; the actual cost of the electricity used is shown by the yellow line that crawls along the bottom of the graph. If you mouse over a bar, the actual data point value will be displayed; similarly, hovering over one of the dots on the grid will show the aproximate cost of that hour of electricity.
Taking the data from the table above during the period where the Leaf was charging, we get the following information:
| Hour | Usage | Cost |
|---|---|---|
| 2am | 1.56 kW/hr | $0.19 |
| 3am | 3.94kW/hr | $0.48 |
| 4am | 3.92kW/hr | $0.48 |
| 5am | 3.93kW/hr | $0.48 |
| 6am | 2.43kW/hr | $0.30 |
| Total | 15.78 kW/hr | $1.93 |
The charge finished sometime in the 6 o'clock hour, and our consumption returned to normal. During the charge, we incurred a cost of about $1.93 at twelve cents per kW/hr; maybe $0.15 of that was for electricity the house was using. What if I had taken my old car instead? Well, I drove around 75 miles. My car got about 30 miles to the gallon, so that would come to around 2.5 gallons. Gas is currently selling for about $3.85 near work, so my commute would have cost me $9.62 instead of a buck eighty. Not bad! Of course, costs can vary depending on the rate plan you sign up for, and whether or not you use solar panels. We'll get into those subjects on future posts.
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