Adding solar power for the new Tesla 3

ADK46

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#1
I don't see any threads on this subject, so maybe it would be useful to describe my own effort on powering my car with solar panels.

I already have a system sized for prior needs, 12kW, which produces about 12,000 kWh/year. (It's not like you multiply by a thousand, it just happens to work out that way for my location and installation details.)

The car will use [15,000 miles/year] times [260 Wh/mile] = 3900 kWh/year. It will be convenient to add 16 300-watt panels to the same roof - 4.8 kW, which will produce about 4800 kWh/year, which will cost (net of all subsidies and tax credits) $4968. I recently added a garage with a split-unit AC/heat pump that can take the excess.

Payback will be 7.4 years. In less rational terms - I'll be telling people that driving the Tesla will cost nothing!

Photo shows existing 12 kW set of panels on roof of our Studio building. Plenty of room to add eight panels on each side.
solarpanels-jpg.13317
 

MelindaV

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#2
I don't see any threads on this subject, so maybe it would be useful to describe my own effort on powering my car with solar panels.

I already have a system sized for prior needs, 12kW, which produces about 12,000 kWh/year. (It's not like you multiply by a thousand, it just happens to work out that way for my location and installation details.)

The car will use [15,000 miles/year] times [260 Wh/mile] = 3900 kWh/year. It will be convenient to add 16 300-watt panels to the same roof - 4.8 kW, which will produce about 4800 kWh/year, which will cost (net of all subsidies and tax credits) $4968. I recently added a garage with a split-unit AC/heat pump that can take the excess.

Payback will be 7.4 years. In less rational terms - I'll be telling people that driving the Tesla will cost nothing!

Photo shows existing 12 kW set of panels on roof of our Studio building. Plenty of room to add eight panels on each side. View attachment 13317
I am jealous that you have that amount of usable roof space!
I seriously considered solar earlier this year and the max space my roof could get was around 15 panels, all willy nilly and hardly more than 3 aligned at any given place ( plus facing east/west ) so in the end decided it wasn't going to work for this house.
 

Fishn4life

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#3
Does NY have any EV rate incentives? I'm a solar designer on the west coast. Depending on the utility company, lots of good night rates for charging our EVs. I'm curious what some of the rates are on the east coast. Thanks for sharing.
 

ADK46

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#4
There's currently some sort of "solarize" promotion, whereby the state (?) gets bids from companies for an area, and selects the best. I don't know whether they benefit just from the promotion, or some other way. My local winner bid $2.65/watt, all in. That's $12,720 for my 4.8kW addition. The NYS direct subsidy is $1660, state tax credit $2760 and the federal credit is $3312.

Last I checked, a kWh cost us $0.14 here. It wouldn't make any sense if we had night rates in NY. It might be coming - I should probably inquire. Haven't signed up quite yet...
 

Nikola

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#5
We use our existing solar array to power the Model 3, since we had some excess capacity. I'm roughly estimating the car will need 2000 kWh/year based on our usage to date (219 Wh/mile).

Our solar array in Arizona is sized at 6.37 kW and produces 11,000 kWh per year, thanks to Arizona's sunny skies and lower latitude. Each year we have about 1,000 kWh left over, which the local utility buys from us at the wholesale rate of just 2.5 cents/kWh. (Meaning, we get a cash credit for $25 each October.)

Since the retail rate here is about 10 cents/kWh it's a far better deal to use the excess power than to get paid wholesale for it. The Model 3 will eat up the surplus and we'll buy an additional 1,000 kWh each year from the utility for about $100.

I would have liked to add a couple of panels to our solar array to make up the difference, but since our system is leased Tesla couldn't change the system cost-effectively, so the payback numbers didn't pan out. Still, $125 per year to fuel our car for a year is a pretty good deal.
 

ADK46

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#6
Same deal in NY, but we choose March for our "anniversary" month - the month we get cashed out for our excess (for peanuts). That's because we need the excess for the long, dark, cold winter. Hint for those living in the frigid north: look into the latest split-unit AC/heat pumps, like a Mitsubishi H2i system. They work even at -20°F.

I looked into the possible move in NY to time-of-use rates. There already is a voluntary TOU program, steered to those with EVs. But I couldn't find the rates anywhere, or if it could be coupled with a net meter. There's a looming switch from the simple "in = out" net metering to something the power companies would prefer - absurdly complicated. I'll be grandfathered but it might kill the PV business. Probably good for EV owners, though.
 

Nikola

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#7
Yeah, Time-Of-Use billing makes no sense if you have solar and net-metering. Net metering means you get 100% of retail rate (whatever it is) for the kWh your system generates, so TOU gives you no advantage. (Unless the utility allowed you to sell power at the higher daytime rate and buy it back at the nighttime rate, but that would be pretty stupid on their part.)

For that reason I haven't yet set Model 3 to charge at night. But if we find that voltage is dropping due to the load of simultaneous air conditioning and car charging, that might be a reason to start charging at night. So far no problems.
 

ADK46

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#8
I have signed up for the additional 16 panels, 4.8 KW.

Before we built on our lot, it was hit by the "Blowdown of 1995", which provided good sun on the studio roof. But a grove of fast-growing poplars have snuck up on the panels, so I've been busy with the chainsaw. If I bury the logs, I could claim to be sequestering a bunch of carbon.

dji_0003-jpg.14284