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Does anyone have a home solar setup that covers all charging?

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
In theory, yes, but it's all tied together. I have a 9 kW solar plant that - on a good day - will generate between 50 and 60 kWh of power, well more than I use on the car. Over the course of a year, it accounts for about 25% of my electricity consumption for my home, including car charging.
 

bonnie

I play a nice person on twitter.
Feb 6, 2011
16,427
9,740
Columbia River Gorge
It looks like you are asking the Model S owners (since you posted in the Model S forum) - but if this was meant to be a more general question, this Roadster owner can tell you it's working just fine. There is an annual 'true up' energy bill each spring where either I owe the energy company or they owe me ... and I received a check for approx $40 this year. So my solar system is covering all of my needs, including charging.
 

tezco

Sig P85
Nov 9, 2012
819
4
Colorado
My 10.4 kW system covers 100% of farm/home use including central AC, the Tesla and a Leaf. (All charging for those is done at home.)
 

Cottonwood

Roadster#433, Model S#S37
Feb 27, 2009
5,088
166
Colorado
Does anyone here have a home solar installation that is large enough to cover 100% of your daily driving? How is it working for you?

Yes, and that is an easy target to hit.

Do some numbers:
  1. 1,000 miles per month driving.
  2. Displayed energy usage of 325 Wh/mi, corrected for vampire and AC charger efficiency to 400 Wh/mi.
  3. That is 400 kW-hr per month or 4,800 kW-hr per year.
  4. Typical production rate in U.S. for grid-tied solar of 1.0 to 1.4 kW-hr per year per DC Watt.
  5. That means that you need somewhere between 3,400 and 4,800 DC Watts of Solar PV to match what your car uses.

As Grid-tied Solar goes, a 3.5 to 5 kW DC system is pretty modest and straight forward.

Adjust these calculations for your driving habits and use PVWatts Calculator to calculate annual output for your location.
 

jkliu47

Member
Apr 30, 2013
459
74
Glendale, CA
If you are planning on adding a PV system to the house to take care of both house and EV needs, a caveat here.

In SoCal, my utility's (Glendale W&P) PV policy restricts residential PV installations to 110% of prior 12 months usage. So, unfortunately because I planned for a PV installation just 2 months after I got my Tesla, I could only install a PV system whose capacity was limited by my prior year's reduced electricity usage due to LED bulb replacements, attic insulation upgrade and only 2 months of Tesla charging.

So if your utility has similar short sighted policies - you may want to time your EV purchase and PV installation accordingly.

So far this year I am running about 7% below PV output required to make me a net zero utility electricity user. Time of Use savings are inconsequential since I am generating all electricity needs during prime time, so for sure I will be paying lowest Tier One rates only.
 

Mike_Schlechter

Model S - P457
May 21, 2010
458
62
Weston, CT
I have a 9.0 system, and spent about $390 on power for the house and car (c. 20k miles) in 2013. I do charge at free chargers and SuperChargers quite often; and I didn't put a meter on my NEMA 14-50 until a month ago. Also, in CT you pay $17 per month just to be on the grid, so really I spent quite a bit less on power in terms of kWhs.
 

Sparky

Member
Aug 13, 2012
557
2,711
Glendale,CA
If you are planning on adding a PV system to the house to take care of both house and EV needs, a caveat here.

In SoCal, my utility's (Glendale W&P) PV policy restricts residential PV installations to 110% of prior 12 months usage. So, unfortunately because I planned for a PV installation just 2 months after I got my Tesla, I could only install a PV system whose capacity was limited by my prior year's reduced electricity usage due to LED bulb replacements, attic insulation upgrade and only 2 months of Tesla charging.

So if your utility has similar short sighted policies - you may want to time your EV purchase and PV installation accordingly.

So far this year I am running about 7% below PV output required to make me a net zero utility electricity user. Time of Use savings are inconsequential since I am generating all electricity needs during prime time, so for sure I will be paying lowest Tier One rates only.

I'm also with GWP. Perhaps, if you installed your system for expandability, after another year your usage will be high enough to add another 10% of PV? GWP records both your PV output and the net value so the previous 12 mos average can be calculated from that.
I suspect the 110% number is somewhat driven by concern for loading of the transformer that supplies your home. Have you explained the recent adjustments to your electrical load (LEDs, EV etc)? When I dealt with them for my PV self-install 6 yrs ago, they were very accommodating to various adjustments to their existing policies. Hope they haven't changed for the worse.
 

Chipper

Active Member
Sep 23, 2013
1,183
22
Chattanooga, TN
I have a 9.7 kWh system and I have only gotten one bill so far but because I can sell excess back to the power company they actually owed me $39.57 after one month's service with the solar. I charge the Model S at home and I drive her a LOT!
 

Ampster

Active Member
Oct 5, 2012
1,753
472
Sonoma, California
I have a 4k system that does not cover all my usage. However, I went on time of use rate with Southern California Edison and by shifting loads I have a zero bill even though I am a net consumer. My monthly bills show negative dollars and positive kWhrs consumption. I get nothing back, nor am i charge anything at annual true up.
 

LucM

Member
Jun 10, 2014
74
5
Westport, CT
In theory, yes, but it's all tied together. I have a 9 kW solar plant that - on a good day - will generate between 50 and 60 kWh of power, well more than I use on the car. Over the course of a year, it accounts for about 25% of my electricity consumption for my home, including car charging.

Wow...how big is your house and/or how many people live in it? I am getting a 9 kW solar system installed and that should be good for over 90% of my useage, before getting the Tesla. I have 3 people in a 4.5k sq ft house.
 

Andrew

Model S #6151, Model 3 #1576
Mar 11, 2013
434
208
Santa Monica, CA
I have a 4k system that does not cover all my usage. However, I went on time of use rate with Southern California Edison and by shifting loads I have a zero bill even though I am a net consumer. My monthly bills show negative dollars and positive kWhrs consumption. I get nothing back, nor am i charge anything at annual true up.

We installed a 5.94KW system in April, with the goal of covering 100% of our house and our car. We drive about 1,000 miles/month, and our house is fairly small and energy efficient (hooray for LEDs!).

So far, we've generated slightly more than we've used each month, and our bills have been negative $ because of the time-of-use rates as well. However, for June, the website shows our projected net usage for the month at 43kWh, but the bill credit will be negative $114! I've been wondering how SCE will handle the TOU true-up if our annual consumption is greater than generation but we have an overall $ credit. Glad to hear it just all zeroes out. (Well, it would be nicer to get a fat check, but I know that's not going to happen!) :)
 

jkliu47

Member
Apr 30, 2013
459
74
Glendale, CA
I'm also with GWP. Perhaps, if you installed your system for expandability, after another year your usage will be high enough to add another 10% of PV? GWP records both your PV output and the net value so the previous 12 mos average can be calculated from that.
I suspect the 110% number is somewhat driven by concern for loading of the transformer that supplies your home. Have you explained the recent adjustments to your electrical load (LEDs, EV etc)? When I dealt with them for my PV self-install 6 yrs ago, they were very accommodating to various adjustments to their existing policies. Hope they haven't changed for the worse.

Since my PV system use panels with microinverters, adding extra panels is straight forward. The problem lies in readjusting the installed panels placement to accommodate additional panels, and the fact that the extra panels will not get additional tax credits or utility rebates. Meaning my payback will increase noticeably, and thus mooting the benefits of the extra PV power.

BTW I love your profile pic - I know where that street is - in Silverlake! Two blocks over there is a Tesla Terrace also. :smile:

Haven't seen your green Teslamobile - only one black, a silver and several whites in my neighborhood (91206).
 

ThortsMD

Member
Nov 30, 2012
321
280
Seattle
I put a 3.8K system up in 2009 which covered about 90% of my needs (I sit in the dark with one LED on dim, small house). When I ordered the car, I put an extra 6 panels up (total of 22 now, 5.2 KWh system). Now, I have a 2.5 mile commute, so a very small daily usage. Before Superchargers and the software upgrade that greatly reduces the Vampire load, I was making about 80% of my needs on an annual basis. But now, I'm back up to over 90%. The reduction in the Vampire load is saving somewhere between 300 and 500+ KWh/year (tough to tell with the changes in how Tesla calculates range over time).
 

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