Vehicle to Home (Ford Figured it Out)

[ajdelange]

There is no natural gas available within 20 miles and propane costs a lot more than electricity and requires a large propane tank and regular deliveries by an ICE truck. It is one of the least sustainable solutions.

First off. thanks for taking the time to describe your system.

I'll note that I originally installed propane as a fallback in case of extended electrical failure. I have a 1000 gallon tank but only come close to using anything near its capacity if the power goes out for an extended period as the tank is that big only to support the generator (whole house) in the case of such an event. If there are no extended power outages the propane (which heats my garage and the apartment above it, supplies backup heat and DHW for the rest of the house and runs my stovetop) lasts a looong time. I'd have to do the sums but around here I think a BTU from burning propane and a BTU from electric are pretty close in cost but I'm guessing that propane is a little cheaper as they seem to install more of that than electric around here. Electric is 13 ¢ a kWh.

My ski cabin has 200 amp service which has been pretty much standard residential service in the US for decades. It's more than enough for my all-electric ski cabin with electric everything including a 60 amp EV charging circuit and 50 amp hot tub circuit. The instant hot water is on three 240V 50 amp breakers. I did an experiment where I turned on everything I could think of (including charging my car and running the mini-split heat pump). Nothing tripped and the main panel connections never got more than warm.

So you have 3 x 50 = 150 + 60 + 50 = 260 A of breakers on a 200 Amp panel plus 30 A each (?) for ovens, clothes dryer and HVAC. That would make a total of 350 plus single pole circuits for lights (LEDs use so little it's almost not worth counting them), outlets etc. Seems inspectors are happy as long as the branch amps are less than twice the panel breaker amps and you seem to be under that.

The Ford Lightning can power low powered devices for multiple days like Ford claimed but most houses have somewhat higher power demands and,

Evidently the mean power demand is 30 kWh/da but, as I pointed out elsewhere, the mean household is not the household buying fancy BEV these days. The households that are do have higher power demand. I use 80 kWh in spring and 150 in winter.

...if you don't want to end up with a completely flat truck battery.

...I mentioned EV charging because that is precisely why I don't like using V2H.

Don't get me wrong. I think relying on V2H for backup is a pretty dumb idea unless you live at the top of a hill and it's downhill all the way to a super charger.

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[rr6013]

A lot of Texas homes have electric heat with resistance wall fan heaters in the bathrooms. In a power outage like Texas experienced recently, you couldn't even heat a moderately sized home for one day with a 100 Kwh worth of battery power (110 Kwh minus 10% for conversion inefficiency).

One of the misleading facets of Ford's presentation was the way they seemed to assume your truck battery is going to be 100% charged when the power goes out. That's not realistic as an EV is almost never kept at 100% state of charge and this kind of power outage is not announced in advance. If you drive your truck home from work and find a cold, dark house, chances are your battery is between 30 and 60% state of charge, not a whole lot to warm it back up if you have electrical resistance heat which is fairly common throughout Texas. Since 2010, 62% of homes built in Texas use electric heating.

And do you really want to draw the battery in your truck down to zero? Then it becomes a big, worthless brick.

I lose power daily in Panama. Its taught the “Essentials” list of things to power on-backup power:
1)Freezer
2)Fridge
3) Well pump(non-City)

Grew-up REC which taught heat you can run a fan on central heating but you can’t start the motor w/o spend-y Big Electrons. SO goose down is your friend those nights.

 

[Crissa]

I can't imagine needing down comforters in Panama, but I suppose if you lived up in the mountains...

-Crissa

 

[ajdelange]

That's really up to the guy who owns the house. If it does the backup supply will have to be pretty stiff.

 

[HaulingAss]

You draw more electricity to take a shower than most houses do in an entire day.

Your demand that your backup power provide for all possible devices exceeds the vast majority of of backup power systems.

I do not demand that backup power provides for all possible devices, I'm simply pointing out how Ford's marketing is misleading when they say their truck has enough backup power to run most homes for days. I have a backup battery system for my cabin and it's only designed to keep the modem and wifi running, my laptop and phone and a few LED lights. It can run those things for three days but it doesn't run space heating (I use a woodstove), hot water (I can heat it on the woodstove) and it doesn't charge my EV (I save it for necessary trips). So I am well aware of how to use an emergency back-up without running the entire house normally. The problem is the way Ford markets this V2H as whole house backup for 3 days. Who starts a power outage with the battery at 100%? And who wants to run their EV down to zero with no way to charge it?

When you speak of how much electricity a house draws in an entire day it implies you are talking about the amount of energy drawn, not the peak instantaneous demand. But I don't think that's what you meant. Because you are aware there is a difference between amount of energy and peak power demand.

I actually use less energy to take a shower than would be typical here because the shower drains through an energy saving heat recovery drainpipe which is particularly efficient in areas with especially cold water supplies. Less than 1% of all houses around here have one of these.

I don't think you make a decent baseline for what's possible. Not only do you not need to take a shower when you're not at your cabin, limiting the amount of power that it requires for standby backup, you've chosen a specifically on-demand system when instead of using more peak power than three houses, you could have chosen a system which meshes with a solar power generation system.
https://www.nrdc.org/experts/pierre-delforge/heat-pump-water-heaters-clean-energy-batteries

Every situation has unique considerations and there is no "one size fits all". My cabin is in the middle of a PNW rainforest completely surrounded by dense mature conifers, some of which are over 200' tall. I get a couple of hours of direct sun in the middle of summer, most months of the year the house and yard are in full shade. AFAIK, there is not a solar power generation system that can work, at all, in full shade.

Backup power does not need to power everything. Nor should it. Some things don't care if the power blinks but still need it all day, others are just pretty, others need an uninterrupted stream, some things need massive power - like your water heater - and shouldn't be used off-grid. Pick and choose these things, and don't say a system can't work because it is not the grid.

I feel like you are lecturing me and that you think I don't know what I'm talking about. It would be pointless to install a heat pump water heater because if I installed it inside the heated envelope my energy savings would be stolen from the room heat 9 months of the year and, if I install the heat exchanger outside it would ice up (even when the temperature is above freezing) because the humidity outside is literally 100% much of the time. Trees transpire water. A lot of water. That would require a heat pump water heater capable of self-defrosting and I am not aware of any that have this feature (and it's not particularly efficient to perform defrost cycles).

But the biggest reason a heat pump water heater would not save any energy is because it would need to be located far from the most common point of water usage, the kitchen sink. Any savings would be consumed by having to run the tap to clear the cold water before the hot water appeared. Trust me, I have investigated this thoroughly and understand the efficiency trade-offs involved. A recirculating hot water system would lose excessive heat in an unheated crawl space even if the pipe was insulated to the max.

While it's true my use case is not typical or representative of every house in the US, it was only presented to illustrate the wide variety of situations and to point out how people could become disillusioned when taking Ford's claims at face value. There is often a lot more to the story.

I do think an EV truck battery could provide a useful source of emergency electricity for low-draw applications but I don't think most people would be happy running their EV's battery flat in a couple of days because they thought it could power their entire house for days. 100 kWh is only about $9 or $10 worth of electricity around here and that's not going to get most homes very far in a winter storm unless you are not trying to power your entire house as if you never lost power.

The real problem is that you might need transportation and want to conserve your EV's limited amount of power. The Ford Lightning can only go around 300 miles and that's assuming you start 100% charged and are driving under favorable conditions. If the battery is flat it is completely useless for anything.

 

[HaulingAss]

I agree, but Ford is not marketing it as for "critical loads", they are marketing it as "whole house power". You and I may understand there is a difference, but the average consumer doesn't know how to calculate electrical loads so they just use what Ford tells them.

 

[Crissa]

Okay, but your house uses the average house's daily power use for a shower, so hence, no, Ford is not lying that their truck can supply most houses for three days.

Averages, how do they work?

-Crissa

 

[rr6013]

Exactly!

All essential backup solar/battery installations can be configured to much more affordable systems that not only pencil but provide that 80/20 sweetspot.

Step in reliabilty, everyone can afford to upgrade their homes to a separate electrical panel to serve “essentials”. No doubt <3kWh systems suffice.

Massive solar roofs, banks of panel arrays ganged Powerwalls are overkill and humblebrag tiling an entire house roof in solar. V2G is not there yet to support VPP ROI. Microgrids will probably accumulate the power to change pricing for better ROI.

Buy what you need. Open invitation for the EE people to calc the Cybertruck factor atop that 3kWh “essential” load.

 

[ajdelange]

I think we can grant them a little wiggle room. They do say that the average house can be supplied for 3 days. The average house uses 30 kWh in a day. That's an average power of 1.25 kW. I find crest factor (the ratio of the peak to average load) to be 8.29 for my electrical use and suppose that is typical. Applied to a 1.25 kW average that implies a peak load of 10.36 kW. Ford's available peak of 9.6 kW compares pretty favorably to this. I think we can suppose that HaulingAss's cabin probably use electricity at something like the same rate as an average house i.e. at 30 kWh per day. But his peak load is 28 kw (assuming nothing else is on when the HWH cuts in). That's a crest factor of 22.4 which is pretty high. Crest factor usually isn't of concern except where one is subject to demand charges and when one is trying to size a backup system as is the case here. Obviously the answer to high crest factor is load shedding. Many an average US house has been backed up with a 5 kW generator. Many a US household can be backed up with a 9.6 kW V2H system. But not all unless the property owner is willing to shed some loads. The hot water heater is not something I would be willing to shed. Every good idea I ever had came to me in the shower. But two people here have expressed willingness to do without hot water or obtain it in another way during an extended power outage. Each situation is unique.

So I'll cut Ford some slack on this. Where I do tend to find them a bit disingenuous is in that "average" Americans don't buy $90,000 trucks.

 

[ajdelange]

There seems to be quite a bit of confusion about the distinction between power, the rate at which energy is transferred and measured in kW, and energy, measured in kWh. If 1 kW flows to a load for 1 hr then 1 kWh of energy has been transferred to that load. Thus, as mentioned in my previous post, a house that used 30 kWh of energy in a day conumes it at an average rate of 30/24 = 1.25 kW. The thing is that electrical systems (be they house or grid) have to be sized to provide the peak load, not the average load. Same for heating, water etc. If your crest factor is 22 you have to install an electrical system capable of supplying 22 times your average load. And the utility has to be able to supply 22 times your average load. This has cost consequences so that one naturally tries to keep crest factor low. But sometimes you can't.

Open invitation for the EE people to calc the Cybertruck factor atop that 3kWh “essential” load.

I'm not quite sure what this is asking for. If your average demand is 1.25 kW and you charge your BEV at 11.52 kW then the crest factor is 12.77/1.25 = 10.2. If you drive 10,000 BEV miles per year at the estimated .4 kWh/mi you will consume 4,000 kWh in a year. The vehicle's average consumption will then be 4000/365.25/24 = 0.456 kW. In other words running your CT 10,000 miles will do the same thing to your electric bill as having 4 100W and 1 60W light bulb on 24/7 throughout the year.

 

[larryboy31]

I think we can grant them a little wiggle room. They do say that the average house can be supplied for 3 days. The average house uses 30 kWh in a day. That's an average power of 1.25 kW. I find crest factor (the ratio of the peak to average load) to be 8.29 for my electrical use and suppose that is typical. Applied to a 1.25 kW average that implies a peak load of 10.36 kW. Ford's available peak of 9.6 kW compares pretty favorably to this. I think we can suppose that HaulingAss's cabin probably use electricity at something like the same rate as an average house i.e. at 30 kWh per day. But his peak load is 28 kw (assuming nothing else is on when the HWH cuts in). That's a crest factor of 22.4 which is pretty high. Crest factor usually isn't of concern except where one is subject to demand charges and when one is trying to size a backup system as is the case here. Obviously the answer to high crest factor is load shedding. Many an average US house has been backed up with a 5 kW generator. Many a US household can be backed up with a 9.6 kW V2H system. But not all unless the property owner is willing to shed some loads. The hot water heater is not something I would be willing to shed. Every good idea I ever had came to me in the shower. But two people here have expressed willingness to do without hot water or obtain it in another way during an extended power outage. Each situation is unique.

So I'll cut Ford some slack on this. Where I do tend to find them a bit disingenuous is in that "average" Americans don't buy $90,000 trucks.

I still don't understand why you are planning on a 30KWH use when you are off the grid. Surely if the grid was down most people would find ways to cut back. I have a sister in law who does not realize that light switches work two ways. She does not understand that they can be used to turn lights off as well. I used an average of 13 KWH per day during the last 2 months. Some months it is less. Maybe an energy audit is in order. I have a propane drier but most of the time I hang my laundry out to dry. Invest in some clothes line and some pins and when the grid goes down you can still dry clothes. When lightbulbs burn out replace them with CFL or LED bulbs. Buy energy efficent appliances. Install a transfer switch so that you can do V2H from your CT or from a generator. I have a large propane tank and my generator runs on gas or propane. Less than two hours of run time will replace a days electrical use from my CT. In addition to shutting off standing lights and unplugging wall warts I will probably shut off all power over night. I should do that sometime anyway just to see how much less power I use. the longest our power has been out was 3 days but if the grid gets hacked or if an EMP occurs that record might be broken by a matter of weeks. Folks that live in hurricane prone areas who don't get a CT and a V2H setup are foolish as far as I am concerned. Hope for the best and prepare for the worst is a good motto.

 

[rr6013]

There seems to be quite a bit of confusion about the distinction between power, the rate at which energy is transferred and measured in kW, and energy, measured in kW. If 1 kW flows to a load for 1 hr then 1 kWh of energy has been transferred to that load. Thus, as mentioned in my previous post, a house that used 30 kWh of energy in a day conumes it at an average rate of 30/24 = 1.25 kW. The thing is that electrical systems (be they house or grid) have to be sized to provide the peal load, not the average load. Same for heating, water etc. If your crest factor is 22 you have to install an electrical system capable of supplying 22 times your average load. And the utility has to be able to supply 22 times your average load. This has cost consequences so that one naturally tries to keep crest factor low. But sometimes you can't.
I'm not quite sure what this is asking for. If your average demand is 1.25 kW and you charge your BEV at 11.52 kW then the crest factor is 12.77/1.25 = 10.2. If you drive 10,000 BEV miles per year at the estimated .4 kWh/mi you will consume 4,000 kWh in a year. The vehicle's average consumption will then be 4000/365.25/24 = 0.456 kW. In other words running your CT 10,000 miles will do the same thing to your electric bill as having 4 100W and 1 60W light bulb on 24/7 throughout the year.

Thank you for the back of envelope calcs!

SO… taking an “essential” load 3kWh + “BEV” load factor 10.2 kWh= 13.2 kWh combined

THEN… 13.2 kWh combined * 150% depecation/cloud-y factor = 19.8 kWh design load (7 300 watt panels)

A solar array 19.8 kWh could then feed 1 Powerwall. That Powerwall would be enough to charge a Cybertruck. But not power truck + house. So Powerwall output would need be dedicated to BEV during charging.

The solar array would service the house and Powerwall during power outage. No idea how a blackbox knows not to have the Powerwall feed house during electricity outage. The Powerwall solar charging would be sacrificial. It would be scavenging electrons when the house had electric power back, supplied by grid. Again blackbox magic.

::Sidebar::
4-5 300watt solar panels could charge a CT? A single Powerwall.

Interesting 5 100W Lightbulbs 24/7 are all the electrons burned (joules) driving BEV

 

[firsttruck]

As has been discussed most backup systems have limitations. For the situation at HaulingAss ski cabin there in more than two solutions (all or nothing). His normal water heater is designed for environment where a grid is available and that grid does not charge extra charges/fees for extremely high peak usages. The water heater he normally uses was picked as best (economic & convenience) in his situation & usage pattern. Backup is a different situation (peaks are very expensive). A third solution would involve small additional investment in water heating equipment and a change to usage pattern during long power outages. During backup periods instead of NO hot water use significantly less hot water and that hot water be at lower temperature. This can be much better than NO hot water. Install a secondary water heater that is much smaller & has much lower peak. Maybe completely different type from what the larger water heater is (ie. small electric or propane water heater with tank). Backup heater only supplies hot/warm water to one bathroom or faucet. Turn on backup heater only when building is occupied and change usage from very hot shower everyday to warm water shower every 2-3 days until grid power returns.

 

[ajdelange]

SO… taking an “essential” load 3kWh + “BEV” load factor 10.2 kWh= 13.2 kWh combined

You are still missing the fact that load is measure in kW - the rate of energy flow to whit the kWh per hour: kWh/h = kW.

THEN… 13.2 kWh combined * 150% depecation/cloud-y factor = 19.8 kWh design load (7 300 watt panels).

If the baseline load is 3 kW and a BEV charging load of 11.52 kW (maximum typical Level 2 though more is possible) then the total load is 14. 52.

A solar array 19.8 kWh could then feed 1 Powerwall.

That's a pretty hefty array: 19.8/0.3 = 66 panels but quite possible. Powerwalls charge at a 5 kW rate so that a 19.8 kW array would require 4 PW to absorb all it produces.

That Powerwall would be enough to charge a Cybertruck.

Four Powerwalls can produce 20 kW. As the charging would have to be Level 2 the fastest they could charge a CT would be 11.53 kW (unless my more or less forgotten fantasy of two charge ports is implemented). Keep in mind that 4 Powerwalls hold 52 kWh of energy which is about 1/4 of the TriMotor battery capacity.

But not power truck + house. So Powerwall output would need be dedicated to BEV during charging.

With a single charge port 4 Powerwalls could charge the CT with 10 kW left over for other loads. A single Powerwall could charge the truck at the 2 kW level with 3 kW left over for other purposes but note that the minimum Tesla solar system requires 2 Powerwalls.

The solar array would service the house and Powerwall during power outage.

It does that when the utility is up. Power from the solar panels goes to the house and any overage goes to charge the Powerwalls.

No idea how a blackbox knows not to have the Powerwall feed house during electricity outage.

That's when the Powerwall does feed the house. The gateway's job is to detect the grid and disconnect the premises from it if it is down.

::Sidebar::
4-5 300watt solar panels could charge a CT? A single Powerwall.

Yes but at a 1500 W rate and only for the 4 - 6 hours of Full Sun Equivalent and only with the battery to buffer it.

Interesting 5 100W Lightbulbs 24/7 are all the electrons burned (joules) driving BEV

I probably drive half the average in a year so for me it's probably a couple of hundred watts.[/QUOTE]

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