Help figuring out solar

[abirozy]

Good morning

For those of you with solar, I would like to ask for your help. I am contemplating solar and am trying to figure out how big of a system i need to recoup the miles my wife and I drive in a year.

1). I primarily drive the R1T and drive an average of about 20k per year. I would say it is an almost equal mix of stop and go as well as free flowing traffic as I drive to work early enough in the morning that I can drive fast on the freeway, but going home is almost always stop and go.

2). my wife drives the Tesla that used to be mine. She drives about 11K per year, similar types of traffic.

3). How big of a system would we need if we want to be able to charge almost exclusively at home on energy created through the system?

We live in Southern California.

Best

Adam

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[Thedude]

Math says you’d need around 1100kw of generation per month to power both. That’s figuring 2mi/kw for the R1T and 3mi/kw for the Tesla, or 20000kw and 3700kw yearly power required.

 

[Madsen203]

Math says you’d need around 1000kw of generation per month to power both.

Probably need 2x that to cover home electricity and variances beyond the wh/mi used. Driving 13k miles last year with a MY but small house, we used 1000kw per month. Winter months are about 1/3 the production rate of summer at best in California. I bet you’ll need a 15kw southern facing PV system to support your base usage.

 

[Madsen203]

Probably need 2x that to cover home electricity and variances beyond the wh/mi used. Driving 13k miles last year with a MY but small house, we used 1000kw per month. Winter months are about 1/3 the production rate of summer at best in California. I bet you’ll need a 15-20kw southern facing PV system to support your base usage. That’s about 45-60 panels.

 

[BrayBay]

Here are a couple links that could help:

PVWatts Calculator by National Renewable Energy Laboratory

Project Sunroof by Google

It would be good to have past data on electricity usage also.

 

[abirozy]

thanks everyone

 

[Budman]

I live in Minnesota. I have 27 panels on my garage roof with the system rated at 7 kW. In reality I get a peak output of about 6 kW in the sunny months because of hazy air/dust on the panel, etc. In the spring/summer months my total daily output can be about 35 to 40 kWh. So, if I put all the solar power collected during 1 day into the Rivian I can add about 30% to the battery pack state of charge. That is less than you might think from 27 panels.....

 

[MoreTrout]

What are you using to charge the truck? The EVSE cable that comes with the truck draws around 7.6 kW. A 40A portable around 9.6 kW and a hardwired EVSE like Rivian sells maxes at 11.5 kW. Your peak output on your array will be around 85% of the size of the system, so with a hardwired EVSE you're looking at a 13.5 kW array at a minimum, and that would go 100% to the truck with nothing left for the house, and only during the peak sun hours of the day.

The NREL calculator link in the post above is probably the best resource to see about what you can expect each month. The best thing you have going for you is being in southern CA.

You might need to rethink your expectations based on the way question #3 is worded. Chances are your system is not going to be capable of providing the real time output needed when charging. But chances are good you can build a system that will get you a net zero balance or close to it over the course of a month or a year. Expect to import a considerable amount from the grid to charge it, but it can be offset by the amount you export to the grid when not charging.

 

[Dark-Fx]

Math says you’d need around 1100kw of generation per month to power both. That’s figuring 2mi/kw for the R1T and 3mi/kw for the Tesla, or 20000kw and 3700kw yearly power required.

kWh*

 

[SoCalTravels]

Good morning

For those of you with solar, I would like to ask for your help. I am contemplating solar and am trying to figure out how big of a system i need to recoup the miles my wife and I drive in a year.

1). I primarily drive the R1T and drive an average of about 20k per year. I would say it is an almost equal mix of stop and go as well as free flowing traffic as I drive to work early enough in the morning that I can drive fast on the freeway, but going home is almost always stop and go.

2). my wife drives the Tesla that used to be mine. She drives about 11K per year, similar types of traffic.

3). How big of a system would we need if we want to be able to charge almost exclusively at home on energy created through the system?

We live in Southern California.

Best

Adam

Sorry don’t have more scientific numbers, but this is how it works for us.

We live in Southern California (SDG&E). Have a 2,900 sq ft home. Run a/c ~5-10 days per year. We don’t use lights/much electricity during the day. Our solar panels generate 11.5MWh of energy per year. The solar panels ONLY cover home energy on a yearly basis. There is no extra/overage.

We are looking at adding more panels and adding battery packs to help offset the energy we are now using in the R1S (but even if we covered 100% of the roof we wouldn’t be able to cover all the R1S energy).

 

[Mark_AZR1T]

Solar Gas Station w/ Off Grid​

Tons of assumptions, but.....at 20K miles per year on the Rivian and 11K miles on the Tesla, you will need to have available power of approximately 11kW for the R1T and 7kW (18kW total charging simultaneously) for the Tesla during daylight hours of max production 3-4 hours, with lower production earlier in the day and later afternoons. Assuming a standard loss of 10-15% in summer over the capacity of the panels. A summer sized system will need to be at least 20-22kW (50 400w panels min).

In the winter you can expect approximately a 40% reduction in energy produced, so for a Winter system, you would need 25-26kW system (65 400w panels min). If you run AC (day) and have a variable speed pool pump that runs overnight, plus all the other basics, I think you will need a minimum of 30kW system.

The one problem with this is of course, you're not making enough excess energy to fill at least two Tesla PowerWalls or similar, because if you're going to have a Solar Gas Station, then you need to complete the mission and be self-sufficient after the sun goes down

Final Recommendation: 40kW Solar System with 2 PowerWalls (min)

 

[SANZC02]

I live in Minnesota. I have 27 panels on my garage roof with the system rated at 7 kW. In reality I get a peak output of about 6 kW in the sunny months because of hazy air/dust on the panel, etc. In the spring/summer months my total daily output can be about 35 to 40 kWh. So, if I put all the solar power collected during 1 day into the Rivian I can add about 30% to the battery pack state of charge. That is less than you might think from 27 panels.....

He will do a little better in SoCal, I have a 6.2 kW system (17 panels) and generated 10.5 MWh in 2022 here in SoCal.

@abirozy you may want to consider some battery storage systems as well. There are also some systems that will only send power to the vehicle when there is excess power be generated by the solar panels, you can research that. An example is Emporia Energy, they have a charger and an energy monitor that connects to the power companies smart meter (works with SCE, not sure what power company you have), you Can add the charger and monitor to the app to only charge when extra power is available.

PM me if you like, I can send you the info for who I used on the solar install. They are in the inland empire but did my system in OC. They were middle of the road on price but very happy with the quality of work and they handled all of the paperwork for permits and inspections including the power company rebate steps (SGIP) for battery system.

 

[Olsonsolar]

Don’t forget there is still a 26% federal tax credit unless they lowered it a bit at the first of the year.

 

[emoore]

Don’t forget there is still a 26% federal tax credit unless they lowered it a bit at the first of the year.

It’s back to 30% until 2032

 

[Olsonsolar]

Damn we only got the 26% in 21.

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