Economical To Trickle Charge Tesla Without Battery? Bay Area

[Xepa777]

Some context:

• Just bought and moved into a Bay area 1950 home where the gas meter is too close to the electrical panel. Every solar company is quoting me several thousand dollars to separate these two + upgrade from 100amp. Annoying. And if I go with solar I don't think I can make it for NEM 2.
• I have a Model 3 that looks to be taking up over half of my monthly electrical bill. We're pretty frugal and don't turn on our AC, just use a space heater / fans when needed.
• Our Tesla uses 3kWh a day on average
• Therefore, I want to go with a very low cost solar system that will just be cheaper than PG&E and not have to do an interconnect. Basically "off-grid."
• PG&E off-peak rate is like $0.47 - $0.57 per kWh based on the month

Let me know your thoughts!

• Thinking of a Growatt SPF5000ES (overkill, but I hear that I'll probably become addicted to DIY and want to grow my system over the years lol, so just future proofing a bit now)
• I can get new Jinko 405w panels for $243 each, maybe three of those?
• Maybe I need a transformer? IDK just a noob here
• Thinking ground mount, can have my uncle build a DIY mount setup for cheap

(1) Is it economical for me to just charge on the weekend with sunlight? Factoring in the 30% tax credit and relatively stable/sunny weather of Palo Alto.
(2) Is it economical for me to implement this plan if I get one of these 200ah Docan batteries (read good reviews on this forum) for $1380 (+shipping) https://www.alibaba.com/product-detail/Docan-power-in-stock-wall-mounted_1600688836971.html

Would appreciate any help from the community

 

[sunshine_eggo]

Some context:

• Just bought and moved into a Bay area 1950 home where the gas meter is too close to the electrical panel. Every solar company is quoting me several thousand dollars to separate these two + upgrade from 100amp. Annoying. And if I go with solar I don't think I can make it for NEM 2.
• I have a Model 3 that looks to be taking up over half of my monthly electrical bill. We're pretty frugal and don't turn on our AC, just use a space heater / fans when needed.

Space heaters are horrifyingly inefficient.

Does your A/C also act as heat pump?

• Our Tesla uses 3kWh a day on average
• Therefore, I want to go with a very low cost solar system that will just be cheaper than PG&E and not have to do an interconnect. Basically "off-grid."
• PG&E off-peak rate is like $0.40 - $0.50 per kWh based on the month

Let me know your thoughts!

• Thinking of a Growatt SPF5000ES (overkill, but I hear that I'll probably become addicted to DIY and want to grow my system over the years lol, so just future proofing a bit now)
• I can get new Jinko 405w panels for $243 each, maybe three of those?
• Maybe I need a transformer? IDK just a noob here
• Thinking ground mount, can have my uncle build a DIY mount setup for cheap

Roof mount will almost certainly require compliance with NEC and need a permit.

UL listing will be required for anything that's integrated into the home power system.

(1) Is it economical for me to just charge on the weekend with sunlight?

by my count, you'll need to provide 21kWh over two days. That will be about 10kWh of batteries and 2-3kW of solar.

Factoring in the 30% tax credit and relatively stable/sunny weather of Palo Alto.

A portable PV charging system will not qualify for a tax credit.

(2) Is it economical for me to implement this plan if I get one of these 200ah Docan batteries (read good reviews on this forum) for $1380 (+shipping) https://www.alibaba.com/product-detail/Docan-power-in-stock-wall-mounted_1600688836971.html

You keep using the word, "economical." This implies that you're trying to save money. Have you run the numbers?

a week's worth of juice costs you:

21kWh * $0.45/kWh = $9.45

For the single battery linked, your payback period will be 146 weeks, and you'll need 2-3 of them along with the inverter and solar. Recommend NOT buying this off alibaba, where you will get ZERO support. Spend < $100 more each and get EG4 from Signature solar or SOK from Watts247 or currentconnected.

Expect a payback period of roughly 10+ years.

Are you doing this for 1) economical reasons or 2) fun?

 

[Xepa777]

Yah my AC acts as a heat pump but we only need it to power the bedroom at night when we're sleeping.

Only doing this for economical reasons. Looks like if I use this only to power the car and possibly our heater that it just isn't economically worth it? Even with used panels off santan?

Is it just not possible to solar charge a Tesla economically is what I'm hearing? Even from the highest electricity state in the US? That's very disappointing.

 

[sunshine_eggo]

Yah my AC acts as a heat pump but we only need it to power the bedroom at night when we're sleeping.

Point is that if you need heat, a heat pump is 5-6X more efficient than space heaters. if your goal is to save money and/or use less electricity, turn on your heat pump. Even small, personal space heaters use a ridiculous amount of juice.

Only doing this for economical reasons. Looks like if I use this only to power the car and possibly our heater that it just isn't economically worth it? Even with used panels off santan?

Even new PV is fairly cheap. The big cost is batteries.

Is it just not possible to solar charge a Tesla economically is what I'm hearing? Even from the highest electricity state in the US? That's very disappointing.

Compressing your charging into the weekend is a big factor. Charging > 10kWh/day costs 3X as much as 3kWh/day. You're putting a week's demand into two days while the system stays dormant for five days.

If you could charge the 3kWh/day, costs would be notably lower. A 5kWh battery and 1-2kW of solar would cover you - even if you charge at night off battery and then re-charge the battery during the day.

You don't need to look any farther than the inverter. $769 + shipping. Assume $0.57/kWh

769/.57 = 1349kWh

1349kWh/3kWh/day = 449 days worth of EV energy.

1 year, 3 month payback period just for the AiO unit with no batteries or panels.

For a kWh/day system:
$800 for inverter
$1500 for battery
$1000 for 2kW PV (1kW would be fine, but weather isn't perfect every day).
$1000 for "stuff"(wiring, mounting, etc.)

$4300

$4300/.$57/kWh = 7543kWh worth of electricity for the same $.

7543kWh/3kWh/day = 2514 days = 6.9 years to break even.

This assumes you can do it completely separate from a dwelling requiring no code compliance. If you have to deal with code compliance, it will be 50-100% more.

If reliability isn't important, you could go even cheaper. Smaller inverter, fewer panels, smaller battery, but cloudy days and intermittent clouds might mean you don't charge that day, or you don't get enough to charge fully.

Even expensive utility power is cheaper than providing your own PV. The ~7 year payback period is better than most.

Most non-DIY residential PV installations have at least a 15 year payback period.

 

[400bird]

If your 1950's California house has the same infamous Zinsco or Zimmerman breaker panels that caused plenty of fires (my 1960's California house did) I'd take them up on the replacement/updated main panel.

I'm a little confused on the power bill.
Your car uses 3kwh /day and is half your bill?
Have you tried charging at night in off peak hours?
Even at $0.57/kWh that's about $50/month.
If you have an off peak rate that could cut the cost in half.

I don't like battery less off grid systems. It doesn't give you any leeway as clouds pass overhead or at sunset as production tapers down.

I'd go for the upgraded panel and go grid tied, hopefully before nem2 goes away.

 

[Luke23]

Get rid of the electric Car problem solved and money saved....your welcome

 

[400bird]

But $50/month doesn't even buy a single tank of gas...

 

[Luke23]

Cheaper than buying a whole lotta solar that cost more than a new car lol

 

[time2roll]

I would go with grid tie solar. 100 amp panel should be able to get a feed in of 20 amps or 4.8 kW. How much solar are they selling you? Many will over sell the system to zero out the electric bill and this is not the most cost effective. Get 3 to 4 kW of solar grid tied and keep the electric panel.

An included battery that can get you through 4-9 pm peak rate could be a reasonable cost effective upgrade.

https://www.pge.com/pge_global/comm...rates-work/Residential-Rates-Plan-Pricing.pdf

 

[Pete@SolarBatteryBarn]

The cheapest setup I have found is to use a GTIL2 (~$400) current limiting inverter.
I use one to run my 240V well (away from the house) and most days it produces 10-12 kWh of power.
I use mine with an Epever CC, 5kWh (Nissan Leaf DIY) lithium battery and six 370W panels.
My payback period should be under 2 years (If the GTIL2 makes it!)

 

[Hedges]

I would go with grid tie solar. 100 amp panel should be able to get a feed in of 20 amps or 4.8 kW. How much solar are they selling you? Many will over sell the system to zero out the electric bill and this is not the most cost effective. Get 3 to 4 kW of solar grid tied and keep the electric panel.

A PV system which delivers less than 100% of afternoon A/C consumption may not be economical.
If your rate schedule will be changed to time of use, then reducing power draw with PV but paying higher rate could increase your bill (despite lower consumption.)

Will no installer connect an inverter to the existing electrical panel? It is full of breakers, located above your gas connection. What's one more?
Get it done under NEM 2.0 and you have a 100% efficient battery for 20 years. Miss the deadline, get NEM 3.0, and you have a 25% efficient battery.

I do second checking for "Zinsco" and replacing if found.

Help me figure this out?

By "loop" do you mean not having a separate neutral from breaker panel to inverter AC in? For my Sunny Island, at least, Neutral and Ground on "AC1" output and "AC2" input are the same net, so I can get away with connecting just one. Or do you mean main breaker panel connecting to inverter, to...

diysolarforum.com

3 kWh/day for the car? To save money, sell your Tesla to some snob (who will benefit the environment more by driving it than you do), and buy yourself a nice ICE car. You are like the little old lady who only used it to drive to church on Sunday, and you won't contribute much to global warming anyway. That Tesla deserves to be driven 100 ~ 250 miles per day.

 

[time2roll]

A PV system which delivers less than 100% of afternoon A/C consumption may not be economical.
If your rate schedule will be changed to time of use, then reducing power draw with PV but paying higher rate could increase your bill (despite lower consumption.)

Yes and this is the Bay Area not Palm Springs. I do quite well in SoCal (semi coastal) to mostly skip the A/C 4pm to 9pm and have just 3 kW of panels.
A 5 kWh battery easily would get me through the on-peak price crunch for normal usage. And yes my A/C goes hard after 9pm all summer. Actually the cooling is more efficient when avoiding the heat of the day too.

Not necessarily a fan of Tesla but I would never choose to go back to a gasser for such a minor detail.

 

[Xepa777]

Point is that if you need heat, a heat pump is 5-6X more efficient than space heaters. if your goal is to save money and/or use less electricity, turn on your heat pump. Even small, personal space heaters use a ridiculous amount of juice.



Even new PV is fairly cheap. The big cost is batteries.



Compressing your charging into the weekend is a big factor. Charging > 10kWh/day costs 3X as much as 3kWh/day. You're putting a week's demand into two days while the system stays dormant for five days.

If you could charge the 3kWh/day, costs would be notably lower. A 5kWh battery and 1-2kW of solar would cover you - even if you charge at night off battery and then re-charge the battery during the day.

You don't need to look any farther than the inverter. $769 + shipping. Assume $0.57/kWh

769/.57 = 1349kWh

1349kWh/3kWh/day = 449 days worth of EV energy.

1 year, 3 month payback period just for the AiO unit with no batteries or panels.

For a kWh/day system:
$800 for inverter
$1500 for battery
$1000 for 2kW PV (1kW would be fine, but weather isn't perfect every day).
$1000 for "stuff"(wiring, mounting, etc.)

$4300

$4300/.$57/kWh = 7543kWh worth of electricity for the same $.

7543kWh/3kWh/day = 2514 days = 6.9 years to break even.

This assumes you can do it completely separate from a dwelling requiring no code compliance. If you have to deal with code compliance, it will be 50-100% more.

If reliability isn't important, you could go even cheaper. Smaller inverter, fewer panels, smaller battery, but cloudy days and intermittent clouds might mean you don't charge that day, or you don't get enough to charge fully.

Even expensive utility power is cheaper than providing your own PV. The ~7 year payback period is better than most.

Most non-DIY residential PV installations have at least a 15 year payback period.

Yah, the point about compressing charging into the weekend days only does make a lot of logical sense.

I guess I will need to do grid tie, which opens up a can of worms for DIY as I'll need an electrician to move my main outlet panel. Sigh. Hopefully I can DIY a ground mount system and panels on my own.

 

[Hedges]

Panels are cheap, permits and contractors are expensive.
Might be better to put in a ground mount array and waste 90+% of its output, have it charge your car when parking and the sun happen to align.
Would be easiest if we could just feed DC to the car, but that takes a fancy gizmo.
How about a batteryless inverter taking in PV and putting out AC?

 

[Xepa777]

Panels are cheap, permits and contractors are expensive.
Might be better to put in a ground mount array and waste 90+% of its output, have it charge your car when parking and the sun happen to align.
Would be easiest if we could just feed DC to the car, but that takes a fancy gizmo.
How about a batteryless inverter taking in PV and putting out AC?

Would a Sol-Ark inverter be able to do this? If I'm creating a non-grid tie system that can be portable, I'm okay spending more money as it's relatively future-proof if I ever move houses.

 

[Hedges]

I'm not certain. Manual does mention no-battery when on grid.
If that does work without battery off grid, might be best with PV strings of multiple orientations, so production exceeds what charger draws for a longer period of time.

Other people here who've used SolArk may be able to answer.

 

[justgary]

I guess I will need to do grid tie, which opens up a can of worms for DIY as I'll need an electrician to move my main outlet panel. Sigh. Hopefully I can DIY a ground mount system and panels on my own.

I take it you are not allowed to pull your own permit? Perhaps you can make a deal with an electrician to pull the permit and inspect your work before The Man comes to inspect it. If you can demonstrate some proficiency, he might go for it. The price would be cheaper than paying his labor and markup on materials.

When I added my shop, the local power co-op gave me a 300A meter base for free since I was upgrading my service and bringing the exterior up to code (by adding shutoffs to each branch). The co-op even came back and crimped the 4/0 lugs for me when I was ready.

 

[HarryN]

I could look at it all with you and kick around ideas if you want. I do some work off grid and mobile power systems.

 

[TomC4306]

Docan batteries (read good reviews on this forum) for $1380 (+shipping)

Look closer. this price for 100 amp hour.