I just got through my first billing cycle with the new hot water heater installed. I'll say right off the bat that I'm very happy with the purchase. During winter, the water was just warm enough for shower taking. Now that its hot out, its plenty warm as I find myself taking cold showers to cool off.
But, the point of this thread is to get a snapshot of power usage and see how things were affected. Below is my spreadsheet I use to track my energy usage (sorry, still no tracker on the site). As you can see, weather wise it was pretty similar to last year this time. I've had to run the window A/C unit a handful of times in our bedroom for sleeping, but during the day we use fans to stay cool. The biggest difference you'll see is the drop from 15 therms of gas to 1 therm of gas. This may not sound like much, but 1 therm = 29.3 kWh of electricity. So, those 15 therms are really more like 440 kWh! That means that the 1 therm I used this July is used for cooking and clothes drying. That leaves 14 therms (410 kWh) for hot water. Considering I only used 330 kWh this July I think it is a HUGE improvement. Of course, I have done a few things since then to decrease electricity usage and I'm sure that helped keeping the electricity usage down. However, the main point here is the green highlighted cells. My total energy usage HALFED from going to this water heater!
EDIT: I know why my electric usage is so low now. Last year at this time had my basement dehumidifier going and this year I did not, I'm sure that has a lot to do with things. Next month will be better compairison. I'm guessing my kWhs will jump to the mid 500s based on the TED info I've been looking at lately. Still a far cry from the 750 kWh combined gas/electric energy usage.