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bwilson4web

bwilson4web

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Project goals:
  1. Lower utility bill
    • No grid connection
  2. Emergency power during extended outage
    • Currently have a 16 kW, natural gas fueled, automatic, emergency generator
My proposed requirements:
  • island operation (aka., no grid connection)
    • the power company can approach me with their plan
  • 10 kWh usable storage - enough to handle 40 miles of EV range.
    • 240 VAC output to derated NEMA 14-50, maximum 6.5-7.5 kW output
    • SOC level, triggered independent circuit: kitchen, hot water, mini-split AC, hall way lights, and furnace fan circuits
  • ~2 kW peak solar array - enough to 80% charge the storage battery on a sunny day
Implimentation thoughts:
  • Used (salvage) EV for battery and backup for primary EV
    • Candidates: Bolt, BMW i3, Leaf
    • Repurpose vehicle power electronics for inverter
  • COTS solar, battery, 240 VAC controller
  • Solar array with mini-inverters to handle shadow and failure isolation
Bob Wilson
 
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Interesting. I pulled my own permit and did my own solar install a little over 2 years ago, but I bought the equipment as a kit from a company up near Shasta. I'd love to also have a battery system but the cost for battery systems is just obtuse. Tesla is the leader (?) but what does one of their power walls cost right now? Near ten grand? Or 14 grand? So somewhere between $750 per kWh to $1000! That's quite frankly outrageous. LFP really should be sub $200 per kWh.

As you point out, getting a used EV battery could be so much cheaper - but a company needs to sell the controller / bridge to let you integrate. Imagine if you could pick up a used Leaf Battery for 10 grand (30-40 kWh), then by a COTS controller for say another 2k. That would be awesome.
 
danrjones said:
Interesting. I pulled my own permit and did my own solar install a little over 2 years ago, but I bought the equipment as a kit from a company up near Shasta. I'd love to also have a battery system but the cost for battery systems is just obtuse. Tesla is the leader (?) but what does one of their power walls cost right now? Near ten grand? Or 14 grand? So somewhere between $750 per kWh to $1000! That's quite frankly outrageous. LFP really should be sub $200 per kWh.

As you point out, getting a used EV battery could be so much cheaper - but a company needs to sell the controller / bridge to let you integrate. Imagine if you could pick up a used Leaf Battery for 10 grand (30-40 kWh), then by a COTS controller for say another 2k. That would be awesome.
Click to expand...
If only could make enough Ford F-150 Lightnings. I read that the Ford F-150 Lightning's battery is equal to 7 Tesla Powerwall backup power units--for a lot less money.
 
insightman said:
If only could make enough Ford F-150 Lightnings. I read that the Ford F-150 Lightning's battery is equal to 7 Tesla Powerwall backup power units--for a lot less money.
Click to expand...
You say it's the equivalent of seven Powerwalls, but you're spending at least $80,000 to get the F-150 Lightning plus home backup setup, which is more than what seven Powerwalls would cost if they're around $10,000 each.

Meanwhile there are some federal incentives for installing solar.
 
Puppethead said:
You say it's the equivalent of seven Powerwalls, but you're spending at least $80,000 to get the F-150 Lightning plus home backup setup, which is more than what seven Powerwalls would cost if they're around $10,000 each.

Meanwhile there are some federal incentives for installing solar.
Click to expand...
Forbes said, "Tesla Powerwall prices start at $11,500 for a single unit," but maybe they come cheaper by the 7.

But you can't add a snowplow to 7 Powerwalls. Oh wait, you can't add a snowplow to an F-150 Lightning, either. I guess it comes down to what you have space for, what you think will be easier to re-sell, who you want to give your money to, and how mobile you want your battery backup to be.
 
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I remember when everyone was certain battery prices were on track to hit $100 per kWh. Doubling that cost for a shell, some extra wiring and controllers, and profit, means a 10 kWh pack should be costing us about $2k. We aren't even in the same zipcode as that price right now. When we actually get there, let me know, because I need a pretty big system to work with my house and solar. My heat pump alone can pull nearly 6kW max in heating mode - and though I don't HAVE to put every device on the battery system, having my heat source on the system seems like a good goal. Not sure how much storage I realistically need - I'd have to look at both peak power, but also a realistic calculation of how long the storage would last with my heat running. But just as a pure guess, I think I'd want to be able to run my heater for at least 4 hours, so that's a 25+ kWh system. At today's prices that would be insane. At ~ $200 per kWh that would be totally do-able.
 
danrjones said:
My heat pump alone can pull nearly 6kW max in heating mode - and though I don't HAVE to put every device on the battery system, having my heat source on the system seems like a good goal.
Click to expand...
I have geothermal heat pump with an propane gas boiler for backup heat, and only the boiler is on my backup power panel. I just had a major power outage and ran my house (boiler, well pump, refrigerator, lights/outlets for main room) off my 8 kW gas generator. I've decided I need to upgrade to one of three options: solar/battery, EV V2H (like F-150 Lightning), or a whole-house automatic standby generator. Not sure what'll cost more, the F-150 Lightning V2H or solar for the house. The generator is the cheapest by far, but it is a fossil fuel solution. Solar would give me true independence from the grid, so it's very desirable.
 
Solar+Battery+Backup will be the way to go with the 30% IRA tax credit. Unfortunately the dealer-installer markup arrangement in America can double (or triple) the cost of solar compared to worldwide installs. The Ford Home integration is just a rebadged Delta Electronics system.

Switching out of natural gas to air source heat pump has added an estimated 25,696kWh/year of extra electricity needs on a 1,200 sq ft home.

AA19gRaX.webp
 
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danrjones said:
Interesting. I pulled my own permit and did my own solar install a little over 2 years ago, but I bought the equipment as a kit from a company up near Shasta. I'd love to also have a battery system but the cost for battery systems is just obtuse. Tesla is the leader (?) but what does one of their power walls cost right now? Near ten grand? Or 14 grand? So somewhere between $750 per kWh to $1000! That's quite frankly outrageous. LFP really should be sub $200 per kWh.

As you point out, getting a used EV battery could be so much cheaper - but a company needs to sell the controller / bridge to let you integrate. Imagine if you could pick up a used Leaf Battery for 10 grand (30-40 kWh), then by a COTS controller for say another 2k. That would be awesome.
Click to expand...
We installed THREE Tesla PowerWalls and they are not as expensive as you think (or indicated). LOL! They have come down in price quite a bit - PLUS, there are SO many Federal (and CA) incentives, that we literally bought 2 and got 1 free, when we did the math.
BEST part of all is despite running 2 refrigerators, AC, dishwasher, washer/dryer, 3 Flat Panel TV's, we were able to run NON-Stop for 5 DAYS when there was a power outage!
AND, we charge our Mach-E AND still get a BIG Monthly check from Edison!
Reco contacting Infinity Solar in ORANGE, CA and get a quote. Worth your time.
 
bwilson4web said:
Project goals:
  1. Lower utility bill
    • No grid connection
  2. Emergency power during extended outage
    • Currently have a 16 kW, natural gas fueled, automatic, emergency generator
My proposed requirements:
  • island operation (aka., no grid connection)
    • the power company can approach me with their plan
  • 10 kWh usable storage - enough to handle 40 miles of EV range.
    • 240 VAC output to derated NEMA 14-50, maximum 6.5-7.5 kW output
    • SOC level, triggered independent circuit: kitchen, hot water, mini-split AC, hall way lights, and furnace fan circuits
  • ~2 kW peak solar array - enough to 80% charge the storage battery on a sunny day
Implimentation thoughts:
  • Used (salvage) EV for battery and backup for primary EV
    • Candidates: Bolt, BMW i3, Leaf
    • Repurpose vehicle power electronics for inverter
  • COTS solar, battery, 240 VAC controller
  • Solar array with mini-inverters to handle shadow and failure isolation
Bob Wilson
Click to expand...
Hi Bob!
Reco contacting either Tesla, directly or Infinity Electric in ORANGE, CA (IF you live in Southern CA.) and get a quote for a total system.
We put in solar panels and 3 Tesla PowerWalls and with all of the Federal and CA incentives, we ended up w/a Buy 2 Powerwalls, get 1 Free - AND the prices have dropped quite a bit as Musk has opened up a dedicated PowerWall plant in NY.
Bottom-line, you may be shocked at how much you will save! Since we are charging a Mach-E, and powering up an A/C, 2 refrigerators, 3 Flat Panel TV's and other appliances, we were happy to find out that during a 5 day power outage, we had full power the entire time! AND, because we are getting BIG, monthly checks from Edison (We also signed up for Edison's supplemental, virtual grid so that when there are power spikes, we give MORE back to the grid!), our Break Even is projected to be less than 5 YRS!!!
 
CA Buttercup said:
We installed THREE Tesla PowerWalls and they are not as expensive as you think (or indicated). LOL! They have come down in price quite a bit - PLUS, there are SO many Federal (and CA) incentives, that we literally bought 2 and got 1 free, when we did the math.
BEST part of all is despite running 2 refrigerators, AC, dishwasher, washer/dryer, 3 Flat Panel TV's, we were able to run NON-Stop for 5 DAYS when there was a power outage!
AND, we charge our Mach-E AND still get a BIG Monthly check from Edison!
Reco contacting Infinity Solar in ORANGE, CA and get a quote. Worth your time.
Click to expand...

If I may, what was your actual cost per kWh? I have a hard time believing it was anywhere near the $200 I think it should be - even if you didn't really pay the face value that the internet gives per power wall, $200 per kWh x 3 power walls would be about $8100 total, installed.
 
teslarati97 said:
Switching out of natural gas to air source heat pump has added an estimated 25,696kWh/year of extra electricity needs on a 1,200 sq ft home.
Click to expand...
Not sure where you got those numbers, but my 2200 SF home in central CO used 1500 kwh last year heating with an air source heat pump.
 
@bwilson4web I didn't see return on investment as one of you goals, but IF your utility has a good grid tie rate, you shouldn't reject it off hand. For me, getting paid full retail for my production and a very reliable grid, and the extra $$ it would take to add battery, I just went with grid tie.
 
teslarati97 said:
Too many -40F days and the backup heat strips have to kick in.
Click to expand...

In a very cold climate, heat strips might not be the way to go - my old house on the east coast I had a heat pump, but the emergency / aux heat was oil. It might make sense in a very cold climate to keep your NG furnace as the blower? YMMV. Where I am now, the heat pump works great, I don't think the aux ever had to kick on except for when I did it for testing. My thermostat keeps track of how many hours the heat pump ran, so I need to go through and calculate, but I would guess around 120 hours Dec-Feb each month, which would be about 2000 kWh. Just a guess.
 
danrjones said:
In a very cold climate, heat strips might not be the way to go - my old house on the east coast I had a heat pump, but the emergency / aux heat was oil. It might make sense in a very cold climate to keep your NG furnace as the blower? YMMV. Where I am now, the heat pump works great, I don't think the aux ever had to kick on except for when I did it for testing. My thermostat keeps track of how many hours the heat pump ran, so I need to go through and calculate, but I would guess around 120 hours Dec-Feb each month, which would be about 2000 kWh. Just a guess.
Click to expand...
Yes a backup NG is far more practical for regions that experience extended arctic winters.

The older 1920 homes around here will use close to 400GJ/year of natural gas for heating while the more modern homes will use 170GJ/year of natural gas for heat.
 
The system came online April 30, 2025 and today is May 31, 2025. Close enough for a first month report.

May 31, 2025, close enough to the first full month of solar:
Solar_05_2025.webp
  • My use: (293.5 kWh + 272.5 kWh) *0.17/kWh = $96.22 electricity savings
    • 79% of solar electricity used by me
    • 21% given "free" to the utility company
Electric car charging:
Tesla_charger_05_2025.webp
  • 523 kWh * 4 mi/kWh = 2,092miles of free EV driving
    • 2,092 miles / 52 mi/gal ~= 40.25 gallons of not bought Prius gas
    • $2.50/gal at COSTCO today * 40.25 gal = ~$100 gas savings
The biggest change is developing new habits of using most of my home electricity once the solar panels start producing enough to match the load. This mean home "load shifting":
  • shower hot water an hour after sun rise
  • clothes washing and drying an hour after sun rise
  • cooking while the sun shines
  • EV charging 10 AM to sun set
    • maximum EV charge rate 20 A to match solar panel peak rate
  • air conditioning afternoon
  • better light and TV usage (turn off what is not in use)
There were two, unusual EV charging events that required drawing grid power. These were associated with testing and tuning my replacement Tesla battery. I won't need to do this again.

Based on the first month, it looks like I'll easily save ~$1,000 per year in electricity costs which matches my expectation.

Bob Wilson
 
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