most bang for buck -EV Charging from solar

[karkit]

I am very new to all of this- I have been trying to learn for about 4 months or so. In Aug, we got an EG4 24K BTU mini. love it!!! I have recently bought a TESLA. I own 15, 400 W Alexus panels. We have not bought an inverter or batteries. I want to know what the best bang-for-buck setup may be to charge my Tesla and run my mini at night. My 200 amp service is 84 ft from my garage, so I was thinking of an off-grid inverter. ? I know a lot of batteries would be needed. Any thoughts, anyone? i am open to suggestions. I am guessing everyone tells me Gridboss, Flexboss 21.
TIA
Karen

 

[Dinobot248]

I'll bite. Please be patient and keep an open mind. Most new folks need to provide more information.


1. I don't own a Tesla so I don't know how fast a level 2 charger goes for a Tesla. Using an optimistic 48A at 240v = 11.5kw for a 50A circuit.

2. Your PV array is 6kw (15x400) so using an very ideal 5 hours of full sun, total daily PV would be 30kw.

3. A useful average efficiency is 72% from lifepo4 batttery from your battery bank to what gets to your Tesla battery. In more techy talk, DC to AC and AC back to DC. Theoretically, if you had a fully charged 50 kwh battery bank, then 36 kwh could make it to your Tesla battery. Charging time would be about 3 hours assume a 11.5 kw max charge rate for a level 2 charger running on a 60a breaker.

Here is some more the math.

Your inverter will operate at 85% efficiency to convert the DC battery to AC power.
Your charging circuit in your Tesla will operate at 85% to convert that AC power from the 50a outlet to DC for the Tesla battery.
85% x 85% = 72%

Feel free to tweak the numbers. Some may say it is 88% and 90%. Efficiency varies with hardware, temperature, battery state of charge, etc, etc. I use 85% as a conservative number and its easier to remember.


4. Prices for batteries range from $75/kwh (DIY) to $200/kwh (pre-built) or more. For a couple of pre-built battteries that make up about 50kwh, then it will cost you $10,000

5. PIck your favorite inverter ecosystem. It really doesn't matter. $6,000 is a good middle of the road budget for the actdual unit(s) only..

6. Hopefully, it is becoming more clear that your limitations are your solar array size (incoming energy) and your battery bank size (how much you can store).


7. Simple math. Spend $40 - 50,000 for a solar system to charge your EV OR just spend $200 a month to charge from the grid and stop at any time if plans / preferences change.

The quick 2 second decision would likely be spend $200 to charge the EV for a couple of months and decide on a long term plan.

There are many benefits and use cases to spending say $50k on a solar system with battery storage. If you work for your money (e.g. are not rich), then try to find more uses..


Hope that helps.

 

[Tuggs]

I am very new to all of this- I have been trying to learn for about 4 months or so. In Aug, we got an EG4 24K BTU mini. love it!!! I have recently bought a TESLA. I own 15, 400 W Alexus panels. We have not bought an inverter or batteries. I want to know what the best bang-for-buck setup may be to charge my Tesla and run my mini at night. My 200 amp service is 84 ft from my garage, so I was thinking of an off-grid inverter. ? I know a lot of batteries would be needed. Any thoughts, anyone? i am open to suggestions. I am guessing everyone tells me Gridboss, Flexboss 21.
TIA
Karen

I use a Flexboss21 and charge my Tesla Model 3 standard range (about 24kw of energy) in the afternoon when I get home, as the sun is going down. My charger is set to 32 amps, it is on a 40-amp breaker from my main subpanel, fed by the flexbos21. I have two of the wall-mount batteries at roughly 14-15 kWh and 6 of the 100Ah server rack batteries. about five kWh each for a total of around 58kwh of storage. Running the house and charging the Tesla puts me at around 28-45% battery left in the mornings. My solar array brings in about 60kwh during September for charging the batteries, and then when they are full, it dumps the rest into the grid for a little net metering. I could do without the grid, but it's there just for peace of mind. If you have a larger capacity Tesla, you would need to adjust your solar input and battery storage accordingly. I do not use a Gridboss for my setup.

 

[OhYou_]

Your charging circuit in your Tesla will operate at 85%

they are actually closer to 95 at 11kw, less efficient at lower amps especially 120v

 

[OhYou_]

I have recently bought a TESLA

which one?
if you bought a cybertruck, there is a fairly cost efficient solution you could do where you use the truck as the battery system.
any other model ehh, unsupported.

 

[BaylentheSky]

With electricity price in Jasper AL at less than 10 cents per KWh, there isn't really an "economical" solution to add battery. The inverter itself plus all the solar panels/wires/etc... already have a 5+ years break even period. If you add a, say, 15KWh battery at the cost of $1800, and at 80% utilization plus 10% conversion loss, you'd be saving 11KWh x $0.10 = $1.1/day. That's about an additional 4.5 years before you recoup the battery investment. In 10 years, so much would have changed, especially in energy storage. I would just invest in solar panels/inverter for now and use them while keeping an eye out for better/cheaper/more efficient batteries.

I live in California where it's $0.73 per KWh during peak hour, and something like $0.45 during off peak, it makes all the sense in the world for me to add battery because my break even period is like less than 2 years.

 

[karkit]

I am very new to all of this- I have been trying to learn for about 4 months or so. In Aug, we got an EG4 24K BTU mini. love it!!! I have recently bought a TESLA. I own 15, 400 W Alexus panels. We have not bought an inverter or batteries. I want to know what the best bang-for-buck setup may be to charge my Tesla and run my mini at night. My 200 amp service is 84 ft from my garage, so I was thinking of an off-grid inverter. ? I know a lot of batteries would be needed. Any thoughts, anyone? i am open to suggestions. I am guessing everyone tells me Gridboss, Flexboss 21.
TIA
Karen

Sorry guys for the vagueness! 2026 Model Y.
Yes my numbers were coming out to 5 yrs as well. They say 0.12 per kwh but my bill reflects 0.175 per kwh.
I appreciate all of the replies! Thanks

 

[Ozark Tinkering]

It seems to me that what will matter more for overnight charging, is what are your daily driving miles? I drove a Chevy Bolt for 5 years, but my daily miles were under 25. I was achieving well over 4.2 mpkW. It doesn't matter what model Tesla you're charging. It's your driving habits that matter.

 

[karkit]

It seems to me that what will matter more for overnight charging, is what are your daily driving miles? I drove a Chevy Bolt for 5 years, but my daily miles were under 25. I was achieving well over 4.2 mpkW. It doesn't matter what model Tesla you're charging. It's your driving habits that matter.

Im driving 80 miles per day, round-trip. 5 days a week.

 

[Ozark Tinkering]

Im driving 80 miles per day, round-trip. 5 days a week.

So you use around 20kW per day? What's your mpkW?

 

[Ozark Tinkering]

So you use around 20kW per day? What's your mpkW?

I think the Lightning only gets about 2mpkW

 

[karkit]

I'll bite. Please be patient and keep an open mind. Most new folks need to provide more information.


1. I don't own a Tesla so I don't know how fast a level 2 charger goes for a Tesla. Using an optimistic 48A at 240v = 11.5kw for a 50A circuit.

2. Your PV array is 6kw (15x400) so using an very ideal 5 hours of full sun, total daily PV would be 30kw.

3. A useful average efficiency is 72% from lifepo4 batttery from your battery bank to what gets to your Tesla battery. In more techy talk, DC to AC and AC back to DC. Theoretically, if you had a fully charged 50 kwh battery bank, then 36 kwh could make it to your Tesla battery. Charging time would be about 3 hours assume a 11.5 kw max charge rate for a level 2 charger running on a 60a breaker.

Here is some more the math.

Your inverter will operate at 85% efficiency to convert the DC battery to AC power.
Your charging circuit in your Tesla will operate at 85% to convert that AC power from the 50a outlet to DC for the Tesla battery.
85% x 85% = 72%

Feel free to tweak the numbers. Some may say it is 88% and 90%. Efficiency varies with hardware, temperature, battery state of charge, etc, etc. I use 85% as a conservative number and its easier to remember.


4. Prices for batteries range from $75/kwh (DIY) to $200/kwh (pre-built) or more. For a couple of pre-built battteries that make up about 50kwh, then it will cost you $10,000

5. PIck your favorite inverter ecosystem. It really doesn't matter. $6,000 is a good middle of the road budget for the actdual unit(s) only..

6. Hopefully, it is becoming more clear that your limitations are your solar array size (incoming energy) and your battery bank size (how much you can store).


7. Simple math. Spend $40 - 50,000 for a solar system to charge your EV OR just spend $200 a month to charge from the grid and stop at any time if plans / preferences change.

The quick 2 second decision would likely be spend $200 to charge the EV for a couple of months and decide on a long term plan.

There are many benefits and use cases to spending say $50k on a solar system with battery storage. If you work for your money (e.g. are not rich), then try to find more uses..


Hope that helps.

Thank you!

 

[karkit]

which one?
if you bought a cybertruck, there is a fairly cost efficient solution you could do where you use the truck as the battery system.
any other model ehh, unsupported.

Model Y

 

[BaylentheSky]

I think the Lightning only gets about 2mpkW

Depending on which version. The Extended Range gets about 2.3M/KWh. The standard range gets 2.5M/Kwh. I have a standard range and get 2.7 average over 52,000 miles driven.

 

[Dinobot248]

Sorry guys for the vagueness! 2026 Model Y.
Yes my numbers were coming out to 5 yrs as well. They say 0.12 per kwh but my bill reflects 0.175 per kwh.
I appreciate all of the replies! Thanks

The best way to compute electric rate is total bill / total kwh. There will be some fluctuations. There are some fixed fees (e.g. $10/mo privilege to have an electric account) that don't rely on actual usage.

Price increases can come in the form of a rate increase based on kwh or a fixed fee.

... but you hit the nail of the head, don't reference the rates given by the electric company. That rate does not include the fixed fees so it will always be lower.

 

[karkit]

I think the Lightning only gets about 2mpkW

Yes I think 25. I have had the car 2 weeks, so I am trying to take it all in. We live in a rural area, and the nearest supercharger is 30 miles away. I will be charging at home. My husband installed the Tesla wall charger Sunday night, 50 amp breaker.

 

[Ozark Tinkering]

Model Y

Check this out. V2L for the Model Y. https://tlyard.com/products/tesla-v2l-discharge-adapter-2kw-4kw-for-tesla-3-y-x-s-portable-ev-power-outlet-with-eu-uk-us-standard-socket?currency=USD&variant=56677240504701&utm_source=google&utm_medium=cpc&utm_campaign=Google Shopping&stkn=db317da8787d&gad_source=1&gad_campaignid=22031848010&gbraid=0AAAAAomSLkEllXaC3B1u4sIzTpgrgtP6N&gclid=CjwKCAjw6P3GBhBVEiwAJPjmLqQu9R2AXw3L-eU_iCjubHcYb0x_dthA0H5Js4uutcsxPsrXxyJ9zxoCSOwQAvD_BwE

 

[Ozark Tinkering]

Yes I think 25. I have had the car 2 weeks, so I am trying to take it all in. We live in a rural area, and the nearest supercharger is 30 miles away. I will be charging at home. My husband installed the Tesla wall charger Sunday night, 50 amp breaker.

I think the Model Y is rated at around 3.4 miles per kW. You can figure your daily usage by that.

 

[karkit]

With electricity price in Jasper AL at less than 10 cents per KWh, there isn't really an "economical" solution to add battery. The inverter itself plus all the solar panels/wires/etc... already have a 5+ years break even period. If you add a, say, 15KWh battery at the cost of $1800, and at 80% utilization plus 10% conversion loss, you'd be saving 11KWh x $0.10 = $1.1/day. That's about an additional 4.5 years before you recoup the battery investment. In 10 years, so much would have changed, especially in energy storage. I would just invest in solar panels/inverter for now and use them while keeping an eye out for better/cheaper/more efficient batteries.

I live in California where it's $0.73 per KWh during peak hour, and something like $0.45 during off peak, it makes all the sense in the world for me to add battery because my break even period is like less than 2 years.

Thanks!
This is what I was coming up with! I can get a Ecoflow DPU at HD with military discount for $8900. The inverter with four 6.1kwh batteries. I thought maybe someken had an idea of how to do something less expensive.
I watched Will's YT video about the 10k solar inverter with the battery for cheap

Depending on which version. The Extended Range gets about 2.3M/KWh. The standard range gets 2.5M/Kwh. I have a standard range and get 2.7 average over 52,000 miles driven.

Dadgumit, yes Long Range, Rear wheel drive.

 

[OhYou_]

Depending on which version. The Extended Range gets about 2.3M/KWh. The standard range gets 2.5M/Kwh. I have a standard range and get 2.7 average over 52,000 miles driven.

what the hell are you doing with it?
Ive done 3.5m/kw in my bolt for 30k miles and my driving is 95% freeway speeds.
and it has the CD of a tractor, teslas should be higher number more efficent at speed.

 

[OhYou_]

The inverter with four 6.1kwh batteries

you need closer to 7 batteries to comfortably replenish the car and run a 24k btu a/c all night.
for the price that thing isnt bad, youre not beating it without going pretty far into diy.

 

[DougL]

I am very new to all of this- I have been trying to learn for about 4 months or so. In Aug, we got an EG4 24K BTU mini. love it!!! I have recently bought a TESLA. I own 15, 400 W Alexus panels. We have not bought an inverter or batteries. I want to know what the best bang-for-buck setup may be to charge my Tesla and run my mini at night. My 200 amp service is 84 ft from my garage, so I was thinking of an off-grid inverter. ? I know a lot of batteries would be needed. Any thoughts, anyone? i am open to suggestions. I am guessing everyone tells me Gridboss, Flexboss 21.
TIA
Karen

It's just a bunch of numbers.... Don't listen to anyone who says you have to charge from a 50A breaker-40A(14-50) circuit. You need to know how many kWh of energy you use daily in your car and for your HVAC. We have 2 EVs( a Tesla and a Nissan ) and charge from solar. Our house on avg( no HVAC ) uses 10kWh/day so I went with 32kWh of battery storage(2 16kWh DIY Basengreen batteries) thinking charging 10kWh in the cars per day would work but it was annoying and left little safety margin for clouds and rainy days. We now have 50kWh of storage(3 16kWh batteries) and charge around 20kWh every other day but also share with neighbors when there's lots of sunshine. This also gives us some buffer for running HVAC.

Calculating how much solar PV input is a whole other ballgame. You have your avg solar hours per day for your area, if there's shading, what slope your roof is, etc. We have ~8kW of solar PV in SoCA in 3 strings with 1 of the 3 shaded in the AM until 10am.

I have a 20A 240VAC circuit for charging the cars at 4kw so that we're pulling 16A for the cars, 3A for the HVAC and then there's room for lights, microwave, induction cooking etc. Our inverter is a 12kW EG4 18kPV.

 

[BaylentheSky]

what the hell are you doing with it?
Ive done 3.5m/kw in my bolt for 30k miles and my driving is 95% freeway speeds.
and it has the CD of a tractor, teslas should be higher number more efficent at speed.

1. I drive in Sports Mode 90% of the time. This sounds counter intuitive at first, but SM has way higher regen rate than Normal Mode.
2. I try not to exceed 25% of the throttle power at any given time. Because the truck is already a speed demon, this 25% power gives me plenty of acceleration.
3. I've owned it for 2 years. That's 2.7 m/KWh of a lot of mixed driving mileage. I don't drive exclusively in the city if that's what you were thinking
4. I set cruise control to 68-69 mph on the highway. Rarely do I get above 70 unless trying to pass. Yes, I'm on the right lane most of the time.
5. If going up an incline, I reduce about 10% my speed at the time, then slowly accelerate back to my normal speed when going back down.

 

[Ozark Tinkering]

I'm powering my level 2 charger with the 10kW SunGold AIO that Will recently did the review on. It's been flawless since powering up on Sept 8th.

 

[OhYou_]

1. I drive in Sports Mode 90% of the time. This sounds counter intuitive at first, but SM has way higher regen rate than Normal Mode.
2. I try not to exceed 25% of the throttle power at any given time. Because the truck is already a speed demon, this 25% power gives me plenty of acceleration.
3. I've owned it for 2 years. That's 2.7 m/KWh of a lot of mixed driving mileage. I don't drive exclusively in the city if that's what you were thinking
4. I set cruise control to 68-69 mph on the highway. Rarely do I get above 70 unless trying to pass. Yes, I'm on the right lane most of the time.
5. If going up an incline, I reduce about 10% my speed at the time, then slowly accelerate back to my normal speed when going back down.

oh i missed it was a lightning, i thought we were talking about Ys lol