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How much "juice" do you use every month?

3K views 8 replies 6 participants last post by  solar_dave 
#1 ·
We are looking at a solar array for our house:

I have a rep from Revolusun coming to give us a price quote for a system for our house. This would be a lease I believe. We are currently using about 13KWH/day. If we add a Chevrolet Volt to the system (and use a full charge everyday) what can we expect. I need to do some research to see what our rate would be if we were to do a TOU rate or if we were to do some other set up. Currently we are paying about the highest rates in the nation for electricity, hence the PV... but what should we bank on? The volt is going to add about 13kw to our current daily use, correct?
Unfortunately the car would be for my spouse, and her commute is NOT fixed. The number of clients she has to see changes on a daily basis. But right now it seems like she is driving at least 800 miles a month... divide that by 40 miles per charge..... and you get 20 charges per month... times 13 = 260kwh per month. So that would be her MINIMUM MONTHLY USE. I seriously doubt her employer will let her plug in at work (she's not there 70% of the time anyhow). And she doesn't come home for lunch often. I don't see any opportunity charges in our future as there is 1 station within 100 miles of us.

Questions:
-Are we going to drive more just cuz we have this awesome car?

-How much juice do you use per charge (assuming min SOC @ start of charge)?

-Should we just size the system smaller and add panels later?

-Should we just get wind generation instead? (joking)

We are getting the car soon, but as you can expect, we gotta get the system in process first as paying HELCO to charge the car is like getting raped daily. One last note, Hawaii has a one to one ratio on net metering as I understand it. They don't mind giving people full credit for juice produced.
 
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#2 ·
Here in Los Angeles, we may have some of the lowest rates available in the nation. I called our LADWP and the rep told me they charge us $0.13 per kwh. Charging the Chevy Volt at my home for 10 hours would cost me $1.30. That is practically free compared to how much we spend on gasoline each month. Our last gasoline bill was almost $1,000.00 for my car and my wife's car. I can't wait for my 2013 Volt to get here from the factory. It shouldn't be too much longer. Maybe another 10 days or so.

Shawn
 
#3 · (Edited)
Adding a solar array is an excellent way to supplement or greatly reduce your electric bill. Not sure how much sun shine you have there but a south facing roof on best. Depending on your finances, adding more panels as you can afford to do is certainly an option.
A grid tied system will allow you to bank or sell back any excess electricity you generate but during a power failure, your solar array will shut down and cease producing power for safety reasons for Power Co. Employees. If you want emergency power during outtages, you will need a grid interactive system which includes a battery backup system and will allow your panels to charge your battery bank until the power returns. If you can afford to purchase, your ROI (Return On Investment) would improve, especially after you own your system. Good luck with your solar system..
 
#4 ·
Actually incremental add can be difficult. Usually you have to go back for the permitting process all over again. It can be done the easiest with something like Enphase micro inverters but size the interconnecting equipment for you final size up front so there is minimal rework.
 
#6 ·
It seems like you have the numbers about right. You've got a good handle on your usage, and a reasonable estimate for the car. With a net metering setup like you described, I wouldn't worry about it - I might even be tempted to oversize the system somewhat if I had the budget, for potential future growth, since they'll apparently be paying you a fortune for electricity.

One challenge you may encounter - a lot of utilities don't want you putting in a system that's more than 10% larger than your historical usage - which of course wouldn't include the Volt or other EV (right now they're all pretty similar in terms of efficiency/power per mile.)
 
#7 ·
Definetly tell the utility you are upping your consumption with an EV and want the extra solar to offset that consumption. In fact you might fib a bit and tell them you eventually want a pair of Volts! :D
 
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