Can my solar array support my future F150 Lighting driving habits?

[CoolViper777]

Your system is similar to mine, so thanks for the comparison. I may just squeak by with enough excess using my 10kW system.

Here is my back-of-the-envelope calculations for 2025. We do 99% of charging at home, and my trips are about 70% city/suburban and 30% highway. We have a 10 kWh (maximum output) system. Total electric use went up about 66% year-over-year. We lease, so I try to keep our annual mileage within the lease parameters, so we drove 10,300 miles last year. Even with the addition of the truck, we still generated more than we used. One factor that works in our favor is being in Colorado and living at 6,000 feet. The sun is intense, especially during the summer. We net produced on average 1.4 mWh/month from March through August.

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[CoolViper777]

22 x 440W panels West facing roof. 3 x 440W panels on South facing roof. The other day, I saw 9kW/second output on a sunny day. Before that, the most I saw in Nov through Feb was 7.8 kW/second. Sun is getting stronger, and I expect I should hit peak soon enough.

On 3/8 and 3/9, I generated 42.3 and 40.5 kWh with my system. From March through end of October, I have NO shade on the roof. From Nov through Feb, I get some partial shade starting around 2:30pm to 3:30pm. It does cut production in half, so I've been thinking about lopping off the top of the trees that are responsible (pine trees).

Be honest, how much power do you REALLY get out of your 10.8 KW of solar? Assuming fixed panels (not tracking) it depends massively on panel arrangement. Residential panels if mounted on the roof are almost always mounted at the same angles as the roof and therefore not likely at the optimal pointing for solar. Since they are not tracking, they are almost never anywhere near pointed in the correct direction. Also in many homes, some of the panels point one way and some point another. In my case there are 28 panels with 10 on one side of the garage roof, 11 on the other side of the garage roof and 7 on the house roof. Next issue is shading. Are there trees that block the sun for all or some of the panels for some part of the day? I my case, I have about 9 KW of panels and here in sunny southern California, about the best I do is 65 KWH in a day. Usually less than that BTW.

The next part is how much power do you REALLY use. Obviously that varies. My consumption is rather high for a single family home with four people in it, and I NEVER generate as much as I use - and that's before adding the Lightning.

 

[CoolViper777]

OP stated 10 kWh excess production, but after rereading in context, maybe they meant 10kW instantaneous production. Those are two completely different things.

10kW instantaneous production, soon to 14.4kW instant production.

 

[CoolViper777]

Well I have 25kWp of panels, no storage and produce roughly 26,000 kWh per year of energy with snow soiling, cloudy climate and shading.

I break even with an all electric house, geothermal heat pump (7500kWh/yr), and a Lightning and two Mach-Es (8000kWh/yr). I think you are fine unless you add more EVs or have electric heat.

Your system is more than double mine. Our heat is gas furnace, with our attic supplemented by a mini-split. Wow, your EV charging year energy usage is 80% of our current household usage. I can see why you have such a large system.

 

[chriserx]

10kW instantaneous production, soon to 14.4kW instant production.

So you are grid tied, with effectively net metering, what's your average monthly and/or yearly use, sounds like more than enough though.

 

[CoolViper777]

I'm typically back home by 12pm to 1pm. So, assuming there is sun, I'd have at least 3, maybe 4 hours of charging time. Even if I come later, my excess get's sold back at the same price I pay for use from the grid, so that's makes my charging from grid doable as necessary.

We would need to know your home power use without the truck.
But with 40 miles daily drive and a mix of highway and slower roads, you can probably count on something like the EPA estimate except when it’s especially cold. An ER battery has an EPA range estimate of 320 miles, so 40 miles is 1/8 or 12.5% of that. And 12.5% of 131 kWh is 16.4 kWh/day. In the summer you’ll use a bit more for AC. And in winter, you’ll use another bit more for the heater. Round it to an average of about 18 kWh/day, 540 kWh per month.

An average energy use per month in PA is about 720-760 kWh. Use 760 kWh/month as an estimate, but it’s a very rough estimate without knowing more about your personal energy use. To get a daily average, 760 kWh / 30 = ~25 kWh/day.

Together, your house and your truck will use about 1300 kWh per month. Again, this is a very rough estimate and assumes you’re driving every day of a 30-day month.

Using this site, you can get an estimate for your solar power production. Plug in your address and other relevant information.
https://pvwatts.nlr.gov/pvwatts.php

Month AC Energy ( kWh )
January 961
February 1,106
March 1,517
April 1,727
May 2,034
June 1,959
July 2,037
August 1,853
September 1,651
October 1,334
November 963
December 828
Annual 17,970

When the sum of your truck and your house energy usage are lower than the number in that rough table, then you theoretically generate enough to replace your driving energy costs.

However, your truck isn’t going to charge for the several hours per day that it’s away from home. You’re not going to want to drain your power station down to zero every night. So, your system is maybe a little undersized for winter generation and full-charging of your truck via solar. If you had a larger home battery (one with enough capacity that it could be used to replace your daily driving energy), you could extend the time you’re able to fully charge your truck from the sun.

 

[TenaciousG77]

I'm in Pittsburgh PA, and the net metering here pays the exact rate I pay for electricity. My current TOTAL usage rate per kWh is $0.198 (this includes generation, transmission and some other fee I forget). FirstEnergy will credit me $0.198 for anything I send back to them. So, it's a good deal.

You're lucky to get a 1:1 credit in dollars. Xcel gives you pennies on the dollar for what you would pay for the same amount of electricity if you want a refund at the end of the year. We do rollover credits, so any excess production goes into a "kWh bank" that we can draw from in the event we use more than we produce in a given month. Helpful for the winter when snow cover and/or short days can really limit production.

 

[CoolViper777]

I believe they put our total usage at approx 14,609 kWh. We should produce 13,278kWh, for a 91% energy predicted energy offset. That's why I want MORE panels. By adding 10 more panels for a total of 4.4kW instant, I would hope my production jumps to 18,589kWh. I think between that and net metering, it should completely (or almost) offset at home EV charging

at

So you are grid tied, with effectively net metering, what's your average monthly and/or yearly use, sounds like more than enough though.

 

[CoolViper777]

I know right? I kept hearing that I will be paid PTC (price to compare). Well the PTC on First Energy's site says $0.126. But when I look at my electric bill, is shows net metering credit is says 10kWh x $0.198. I was very pleasantly surprised.

My solar installer says that once I get above the projected usage amount, it will drop to wholesale. I'm still not clear on what exactly the "above projected usage amount" means. Does that mean that once I sell back more than 14,609kWh, then my price goes down? Or the combined total of my total usage + total excess sold back exceeds 14,609kWh?

You're lucky to get a 1:1 credit in dollars. Xcel gives you pennies on the dollar for what you would pay for the same amount of electricity if you want a refund at the end of the year. We do rollover credits, so any excess production goes into a "kWh bank" that we can draw from in the event we use more than we produce in a given month. Helpful for the winter when snow cover and/or short days can really limit production.

 

[TheDuck]

I want to get a Lariat with the ER battery. And I want to always charge from my solar panel excess energy, at least as much as possible.

I have a 10.8 kW solar array with Tesla Powerwall 3 (13.5kWh) battery. I'm am shortly adding another 4.5kW of panels, for a grand total of 15kW.

My daily driving habits are 20 to 40 miles daily, with me working from my car between 2 and 3 hours daily on average. The driving is a mix of some interstate highways and local road. Being in Pittsburgh, it's not too cold, unless you are talking Dec through Feb.

So, I wonder, how much battery % does the ER battery use daily, for this scenario? I'd be running the heater in the winter, and A/C in the summer. The milder months, probably just crack the windows when possible.

For the summer, I should produce close to 15kWh solar energy when sunny, maybe 1/2 that on a more cloudy day, and 1/4 that on a rainy day. Probably around a max 5-6kWh of house energy usage. So, on a sunny day, that leaves me with maybe 7 to 10kWh of excess, and less on other days

Any thoughts are appreciated.

 

[Jiji]

Your system is more than double mine. Our heat is gas furnace, with our attic supplemented by a mini-split. Wow, your EV charging year energy usage is 80% of our current household usage. I can see why you have such a large system.

Not after you upgrade.

Sanity check, 8000kWh times an estimated fleet average of 3 mi/kWh is 24,000 niles. That 8000kWh is measured at the panel, more like 7200kWh in the batteries after charging losses.

 

[K6CCC]

I'm in Pittsburgh PA, and the net metering here pays the exact rate I pay for electricity.

So am I here in SoCal. However as I understand it, new people are not getting 1:1 Net Metering.
I am also on a Time of Use rate, so from 1600 - 2100, my rate (in or out) is about 2.5 times higher than the rest of the day. Unfortunately that is also the time of day that the large tree in my back yard shades about 2/3 of the solar I am also looking into reducing the size of that tree...

You may want to look at your utility to see if they offer ToU rates and it would be beneficial. If your off peak rates are at night (often the case), you may be dollars ahead to sell lots of power during peak rate from your solar and charge the truck at night on the off-peak rate. Depends on the ToU rate structure. Also make sure that changing rate structure does NOT affect your Net Metering.

To clarify, my current system is a 10.8kW instantaneous peak system. In other words, when sun is at peak, it will produce approx 10kW per second.

A little terminology. Please take this as education, not criticism. MANY people get this wrong...

The 10.8 KW rating for your solar system is a rate of generation. Time does not affect that rate, so drop the "per second" and "instantaneous peak" from your description. KiloWatt Hour is an amount of energy so 1 KWH means 1 KW for one hour - or 0.1 KW for 10 hours, or 10 KW for 0.1 hours, etc. Therefore if your solar was actually producing 10.8 KW, and did so for exactly 4 hours, it would produce 43.2 KWH. Similarly, if your truck is getting 2.0 miles per KWH (I'm going to make the math easy) and you are driving 60 MPH, you would be consuming electricity at a rate of 30 KW (about 40 HP), and if you drove for three hours at that exact consumption, you would use 90 KWH of electricity (about 69% of an Extended Range (131 KWH) battery). To replace that 90 KWH would take about 9 hours if you were using an EVSE that will supply the full 48 amps that the on board AC charger can draw. Or at a DC Fast Charger that averaged 120 KW charge rate, it would take 45 minutes (the charge rate on a DC Fast Charge will almost certainly vary over the course of the charge session - hence the reason I said averaged).

 

[K6CCC]

Sanity check, 8000kWh times an estimated fleet average of 3 mi/kWh is 24,000 niles. That 8000kWh is measured at the panel, more like 7200kWh in the batteries after charging losses.

3 miles / KWH is being VERY optimistic. The people who deal with seriously cold weather will drag the fleet average down a lot, but even here in southern California, my first year averaged just a hair over 2.3 mi / KWH.

You are correct about the 8000 KWH at the AC panel being ABOUT 7200 KWH to the batteries is about right.

 

[Jiji]

I believe they put our total usage at approx 14,609 kWh. We should produce 13,278kWh, for a 91% energy predicted energy offset.

I hope I am wrong but seems like the production estimates might be high for Pittsburgh. Similar latitude to me in the NY Finder Lakes, similar weather too. Mine are ground mounted so perfect south direction and optimal pitch, roof determines these values and likely less than optimal.

This Dec I did 571 kWh, same as they estimate for you and I clean , off the snow if the forecast is for a day of sun, 6 years of data the Dec range is 571-770 kWh. Hope they are accurate, I certainly know you can't have more cloudily weather than I do.

 

[CoolViper777]

My time of use rates don't seem to be that great when I last looked, so it seems like keep my normal rate is a better option.

As for the kW versus kWh terminology, I'm aware of the difference (I'm an Electrical Engineer! . I just used kW/second in an attempt to make everyone aware that is was the instantaneous rate of generation, as there seemed to be some confusion what I mean when I said my solar system was a 10kW system.

The terminology can be confusing.

So am I here in SoCal. However as I understand it, new people are not getting 1:1 Net Metering.
I am also on a Time of Use rate, so from 1600 - 2100, my rate (in or out) is about 2.5 times higher than the rest of the day. Unfortunately that is also the time of day that the large tree in my back yard shades about 2/3 of the solar I am also looking into reducing the size of that tree...

You may want to look at your utility to see if they offer ToU rates and it would be beneficial. If your off peak rates are at night (often the case), you may be dollars ahead to sell lots of power during peak rate from your solar and charge the truck at night on the off-peak rate. Depends on the ToU rate structure. Also make sure that changing rate structure does NOT affect your Net Metering.



A little terminology. Please take this as education, not criticism. MANY people get this wrong...

The 10.8 KW rating for your solar system is a rate of generation. Time does not affect that rate, so drop the "per second" and "instantaneous peak" from your description. KiloWatt Hour is an amount of energy so 1 KWH means 1 KW for one hour - or 0.1 KW for 10 hours, or 10 KW for 0.1 hours, etc. Therefore if your solar was actually producing 10.8 KW, and did so for exactly 4 hours, it would produce 43.2 KWH. Similarly, if your truck is getting 2.0 miles per KWH (I'm going to make the math easy) and you are driving 60 MPH, you would be consuming electricity at a rate of 30 KW (about 40 HP), and if you drove for three hours at that exact consumption, you would use 90 KWH of electricity (about 69% of an Extended Range (131 KWH) battery). To replace that 90 KWH would take about 9 hours if you were using an EVSE that will supply the full 48 amps that the on board AC charger can draw. Or at a DC Fast Charger that averaged 120 KW charge rate, it would take 45 minutes (the charge rate on a DC Fast Charge will almost certainly vary over the course of the charge session - hence the reason I said averaged).

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