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Is that the transfer switch just for the furnace or the whole house? I was staring at my furnace yesterday, trying to figure out what to do if power stops and temperature drops below freezing. Doing the whole house transfer switch is too much, esp given o don’t have a 30amp power source, but it never occurred to me to do just the furnace.

You're definitely right on the tinfoil hat angle. Vehicle to home is inevitable, but the rollout is intentionally slow / designed to fail, so the utilities can keep milking folks and justify their natural gas peaker plant investments. Also, once it works, vehicle to home will immediately tank the grid-storage and home-storage battery industry.

Some company is going to create a gray-market "high voltage -> top N home battery systems" dongle that you can just wire into the battery pack on your car. That company will make a fortune (but only if they're able to dodge liability).

I've heard of people doing similar with old prius beaters. You wire the 500V (or whatever) DC battery into an inverter, and then plug your fridge, etc into it. Leave the car ignition on, and it runs the gas engine for a few minutes an hour indefinitely because it sees the drain and thinks you are driving it.

Most modern EV's support this sort of thing officially, but they're hardwired to one brand of house battery. So, when you buy a new car, I guess they think you will throw out your house solar panels and backup battery. If you want two cars, then I guess you get a divorce?

> My tinfoil hat [...] the relationship between energy providers and law makers

My local establishment's energy czar is also on the board of the electric company (itself a natural monopoly of course).

No tinfoil hat required. They have re-elected her several times as well.

Batteries alone are not suitable for long duration outages, but solar+batteries, designed correctly, can not only supply enough power during long outages, it can get you to be off-grid entirely in the first place at a dramatically more cost effective number than your $500k quoted - perhaps 1/5 or less for a system suitable for your needs of 115kWh per day. So while the system might be more expensive than a generator alone, it can still beat on value because it provides power all year round.

You also do an unfair comparison here - you are OK with portable batteries providing only fridge & WiFi for a couple hours, but expect whole-hole batteries to last a week. Many people use whole-home batteries to bridge typical outages that last <24 hours, and do so without ever having to notice any change of use of their home - powering their full heating/cooling etc.

Batteries and generators are also not mutually exclusive. You can install a solar+battery system because it makes economic sense and pays for itself while providing zero-downtime backup for most outages, while also backing that up with a generator for longer term edge case outages eg long extended outages during the winter or where there is an unusually long “solar drought” - it really depends on how much resilience you are designing for.

You don’t need to run your 5+ ton HVAC full time. Get an EV and run the AC there (no more than 3kW). Sleep in the EV. A typical 80kWh EV battery will last several days. And this is not just theoretical; plenty of people have done this.

For Christ’s sake a natural disaster just struck and you want to live like nothing happened? The entitlement is unbelievable.

Assuming you have enough solar, how about running your 5+ ton HVAC system only when there is enough production? And properly insulating your home, of course, using it as a thermal battery of sorts.

If there is a grid outage, surely one can shift consumption to solar production hours while using the battery for the always-on systems (fridge, lights, some computing...).

>I think a simple generator on an ATS remains undefeated from an engineering perspective.

Let me just inject a bit of nuance here to avoid what I think is an unintentional sleight if hand...

For the small sliver of the population that lives under threat of a large area week long blackout in a hot humid climate, I think a simple generator on an ATS remains undefeated from an engineering perspective.

For the vast majority of the population, it's incredibly rare to lose power for that long, and need AC 24/7 afterwards. It basically only happens in the gulf.

> am not aware of any economically feasible way to run my 5+ ton HVAC system full-time on batteries after a hurricane just reset all the infrastructure, and you do need to run it full time because of the insane humidity and latent heat that follows a tropical system.

Which region is this?

Are hurricanes that reset all the infrastructure a recent phenomena in this region? How did people manage in the 60s, 70s, 80s, 90s etc before these rather large (5+ ton HVAC) were even an option?

>Doing the math, I'd need something approaching 800kWh of storage to ride through this kind of event (7+ days)

How airtight is your House? You may be better off with a tighter house to reduce the infiltration load from the outdoor air and possibly section out the house so that post hurricane the primary living spaces are the only spaces that are constantly getting fresh air and there fore humidity load and for the non primary spaces, you dehumidify once and hold it there.

>I think a simple generator on an ATS remains undefeated from an engineering perspective. If you have an air cooled unit

Yes, if your outages are under lets say 10 days a year a generator + fuel will be orders of magnitude cheaper wrt TCO, unless your grid is super expensive.

You average 100kWh of use per day?

What’s 5 ton in new money, 5kW power draw max? Are you planning to run that full power for a week?

Yes, that much in batteries would cost a lot but uk prices right now would be ~87.5k for the batteries themselves (so a shade over $100k I guess). £7k for 64kWh

You’re not going to run HVAC, but I’m more than happy to have the freezer running, the light on the TV etc

Batteries are for load shifting between day and night and for short term backups. Yes, 7+ days of outages do require means of replenishing the battery, whether it's from a diesel unit or a solar. That's not a battery cost problem.

Yeah it's hard for batteries alone to compete with generators, unless we put a lot of weight on things like noise, or are just focused on small loads like fridges.

I think the more interesting comparison is generators vs solar, though it depends on the local weather etc.

I have a 100kwh battery (my car, Zeekr 7x, in Australia). That can run quite a few days or even a week with careful usage.

This is exactly what the post is trying to address: during a serious long-term outage, batteries on their own will run empty. What you need is the ability to recharge batteries from solar during an extended outage, while also flexibly drawing from the batteries when solar isn't enough.

I’ve been looking into a smaller scale option to run limited items medium term on part time hours…

Best option so far involves a mix of batteries that are charged from the mains when available and topped up from a mix of solar and a LPG/multi-fuel generator.

But unless you want to go very large on the solar and generator size it’s unlikely to cover everything full time.

You can run a fridge, natural gas furnace and some lights for a few days on 5kWh (I've done it a few times).

EVs have 60kWh+, which should get you through a week (if not two) easily.

You can run your hvac fan and an oversized dehumidifier for a while off batteries. You don't need the whole hvac system.

I have 18kw of solar and 30kwh of batteries with a 5ton ac it will run it will run indefinitely assuming the sun comes out, if it doesn’t I have a chargeverter that can keep the batteries charged off my RV’s diesel generator or gas portable.

My solar system generates excess power daily and has zero maintenance, the generators are pure money sinks for backup power and require regular maintenance.

Options are nice.

Also heat pump water heater and dryer help reduce load along with efficient variable speed hvac and good insulation.

Fuel is a problem during a storm too and a buried large propane tank is a good way to go but very expensive on top of installation.

An electric car with bi directional charging would add to flexibility either charging from home system or being able to go find power and bring it home.

Ideally I would like a gasoline hybrid with power out like a F150 power boost and a fully electric with large battery and V2L any Tesla would do now as they all have 2400w out I believe Cybertruck can do more. My chargeverter can take 120v or 240v

How about reducing energy use? In general, but then especially after a grid-destroying event that keeps you offline for a week? You surely don't need to have everything HVAC running on full blast in the whole house during that time. And your laundry and next oven long cook can probably also wait until the grid power is back.

If you then add some solar into the mix, it doesn't sound as dramatic anymore.

There is something in between flashlights and a grid scale battery that van power your full electric home.

I just have a plugin battery that I can run the lights, fridges, phone chargers off of for 24 hrs. That is good enough for me, and I think most people. Anything shorter, and it's not necessary to run the rest, much longer, there also isn't because apparently shit hit the fan and we're not necessarily assuming the power comes back on in the next weeks or ever.

> and you do need to run it full time

Or what? Are you made of salt or sugar?

That's a valid concern for you where you are.

For me where I am, things are different. We don't get hurricanes here.

Our longest power outages tend to follow ice storms. We need heat because these things happen in the winter time when it's cold outside, and that's dangerous for various human and infrastructure reasons (pipes freezing and breaking).

But I use natural gas for heat and I don't recall ever having a weather-related natural gas outage. So that's helpful. And ice storms tend to happen when it's cold, but not damn cold -- that helps, too.

My furnace uses about 600W of electricity while running. It does not run all the time. According to my charts on a random day/night cycle last February with a high of -8C and a low of -16C, it was running with an average duty cycle of about 30% over that period.

600 Watts × 30% × 24 hours = around 4.3kWh for that 24-hour period, just for heat.

I'll also need to keep the fridge cold, and some lights running, and will surely be getting some use out of a laptop and some network stuff.

A common-enough home battery size is 48v, 100Ah, or 4.8kWh. They cost around $1,000 right now (some more, some less) in DIY-friendly shapes.

As a spitball effort: If I live more-conservatively and dial back the thermostat (it is a power outage, after all), I can probably get enough power to live a productive, comfortable-enough life on one such 4.8kWh battery, per day. Ish. If I'm careful.

So for batteries, alone, I'm at $1,000 per day. I'll need an inverter as well. That can be either minimal or extensively integrated, grid-tied or not, solar-accepting or not, and etc. Let's just pin that at $3000, with the wiring and accoutrements, and assume I'm doing the labor for free.

I'm now at ~$10k to survive a week of power outage at home in the winter on batteries alone. That's expensive[1], yes, but a whole lot less than half a million bucks. A whole lot less than a very nice, installed, low-RPM generator, too. :)

...except, realistically: It's more like $13k for a week, because future-me will surely not be as careful with energy use as present-me suggests that I should be and 3 more batteries adds some safety capacity. :)

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And that can be supplemented. Solar input can obviously be used (if available), but may be limited by winter sunlight conditions and storm accumulation.

Gas-fired generators can also be used. An inexpensive-ish portable inverter generator does the trick well when combined with, say, an EG4-6000XP do-all inverter.

That particular inverter wants to see at least 2 of these batteries connected, so let's play with that minimum: 2 batteries, 1 inverter, 1 generator. ~1.4 batteries worth of load every 24 hours, as with the safe $13k figure above.

The generator can be run pretty hard (it has a continuous max rating for a reason), and it can be run intermittently. The EG4 allows programming of generator input power.

So let's pick a generator: Champion 201509. It can do 7kW continuous, and we'll load it to 75% of that, or 5,250 W. From this 5,250W, it provides for the house's present consumption while it runs, and it restores the charge of the two batteries to 100% SoC[2].

If it is run once per day, it can do this job in about 2 hours and then be switched off until tomorrow.

If it runs like this once per day for a week, I guesstimate that it uses about 11 gallons of gas over this week. That's a very manageable quantity of fuel.

So we're at $2k for batteries, $3k for inverter+stuff, and $2k for an appropriate generator. That's $7k to run ~indefinitely, or as long as I can keep bringing in fuel, with enough power to survive a blackout (with heat, lights, refrigeration, some entertainment) long-enough on batteries alone for the roads to become passable and then decide if I'm making a run to fill up the gas cans with fresh fuel.

Not so bad for a relatively quiet time of living in a temporary blackout, and the house gains a gains a big UPS for some stuff (which is nice). (The installed gear also offers an easy entry into solar power.)

But I'm not in hurricane country. And while I do love me some aircon, our summers are pretty survivable, usually. My needs are not the same as your needs are. :)

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[1]: Except, for the price of this kind of self-sufficiency: Draining/blowing out the plumbing and staying at a hotel or with friends/family for a few days in an unaffected area might be a better option. The cheap portable air compressor I have doesn't leak down at all, so it's always got a full tank of air while just sitting there unplugged. I'll figure something out: Power outages are very quiet, creative times.

[2]: 100% SoC? Yep. It's a temporary blackout where the batteries are operating as a UPS, not a long-term operation where the typical 20%-80% SoC goals are important for longevity. They won't stay at 100% for very long, anyway.

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Oil generators have an “artificially” low price because there’s a lot of demand for oil for other things. If the other sources of demand go away, the price may become unfavorable even if gas generators make a lot more sense from a redundancy perspective.

You can't do just V2H, but Enphase and others have moved to simpler meter collars and grid disconnect for exactly this reason.

The main question for this thread remains who the Enphase / ISO standards friendly OEMs will be. With Tesla saying they'll allow it now, maybe others will get onboard, but the risk is that they wall themselves off.

It’s unfortunate and inconvenient. However A transfer switch requires <3 minutes to engage. If a car was able to supply 30-50 amp via compatible plug it would work reasonably well even absent unified v2h standard.

Most recent teslas support 20amp at 120v output via official $100 cable adapter. Some other cars support about 20amps too, eg RivianR2. While it falls short of desirable amperage the car manufactures can bridge the gap if they wanted to. Even now I can run the bare minimum of workloads - a full size fridge, a small AC or Microwave, LED lights, and phone chargers.

V2H can charge home battery systems, but V2L "cannot". There's obviously a market for "plug the 240V outlet on my EV into my house battery. Use the car to charge the house battery while the house is running off the house battery".

Someone will make it work.

So they always had it, just disabled in software?

I don't think either of those are real concerns. The free supercharging did not overlap with homes that could be charged by cars.

Also, safe islanding devices have been very standard for at least 5-10 years. Policy 1: House watches incoming voltage, and turns off the breaker if the grid is down. House electricity + solar stay on; line to power company stays at 0V. Policy 2: Panels see that the house voltage is low, so they turn themselves off.

Policy 1 requires an electrician, but mostly just for permitting. I'd guess a good fraction of the people reading this could safely do it themselves after reading a manual. Policy 2 does not require an electrician or understanding electricity at all. It's how DIY balcony solar usually works.

As far as I can tell, the Leaf never had this in the US. The 1st and 2nd gen hard the hardware, but the chargers weren't there. And the 3rd gen has only announced V2L.

From my perspective, "zero-interrupt automatic transition" is not that important, but being able to have the system smoothly move between having the solar recharge the car and the car power the house during an extended grid outage is critical.

How does solar recharge your F150 with this setup?

And then after a little while you can be without power AND stranded!

No, the main barrier is concern over warranties for the vehicles.

In California, the law requires that vehicles still hold up to 70% of their original charge after 8 years and 75% in the future [1]:

> and d., to deteriorate to less than 70% for a warranty period of eight years or 100,000 miles, whichever first occurs, for 2026 through 2030 model years, and 75% for a warranty period of eight years or 100,000 miles, whichever first occurs, for 2031 and subsequent model years.

The law is unclear on bidirectional charging and whether this would give manufacturers an out. So they're cautious.

[1] https://www.law.cornell.edu/regulations/california/13-CCR-19...

In TX, the power producers, distributors, and retail electric utilities are (most commonly) different parties, so the latter two are very much interested in the type of decentralized time-shifting you mention since it smooths wholesale costs somewhat and reduces grid buildout and maintenance.

For EV owners in TX, its not uncommon to have fairly free charging overnight (just paying the distribution costs of 5-6 cents/kWh).

For homes with residential solar and batteries in addition to the EV, you can have essentially free power and EV charging due to time-shifting and incentives.

Residential batteries are still quite expensive, though, so it would be amazing to recruit those in the above EV to time-shift using V2H.

Why? That's the entire point of moving towards dynamic tariffs. In the systems I'm familiar with the utility company makes money through a fee charged on top of the market purchase/sale price, much like an investment broker.

V2H was popular among Japanese Nissan Leaf owners and there were tons of Leafs on cinderblocks with dead batteries used to milk incentives sold on used market for like $1k with 10 mi on the meter. Tiny household sellers are credited for sales for generosity, but apparently often just a noise that needs to be compensated by increasing power output at power plants to then just burn off. Great idea on paper, often not so much in practice.

Maybe. I did the math and in our area a Powerwall would roughly pay for itself over the speced lifespan of the device, IIRC that was just the cost of the device not the cost of installation. I did that calculation ~4 years ago, so maybe it has changed, but definitely do the math, I was surprised.

Why shouldn't utilities pay for this? You're provide grid load balancing. Theoretically their pricing should be considering this? It's not actually free to you since charging and discharging your battery costs money.

But naturally the situation is they want to be the ones paid the big bucks for such services.

CHAdeMO had that spec, but of course is obsoleted now.

If I understand things correctly tho many of the V2L solutions just work with pretty much any car that does CCS, regardless of whether the manufacturer officially supports this or not. My Polestar2 for example doesn't official have any kind of V2H/V2L option but I've heard of many success stories.

When I was living in the PNW and had a 5 day power outage due to a windstorm, my PowerShare/cybertruck made life so much better. Nat gas water heater, furnace, and stovetop definitely helped. Had options to top up the charge too, took the kids to a play date at a house that let us charge, and I had a nat gas generator that worked well to charge the truck too.

New builds in WA state don’t get nat gas anymore though, so people will have to be a lot more careful about using appliances during an outage.

> I have an islanding system for my (house) battery and solar, so in theory, I could have a bidirectional charger whilst being off grid. However both my car and charger don't support that (my charger is also deeply shit, and has no local API access

...

> The amount of sysadminig to make that work reliably means that no normal person is able to achieve it. The problem for consumers is that there isn't any motivation for manufactures to work together on this. because they want to vertically integrate.

We are in a very similar position. The issue is every company in this area is like you say: deeply shit with limited local API access. Setting up bidirectional charging in the UK is technically, really not that hard, especially with islanding handled at the household level.

Good luck trying to get someone willing to put their career and certifications on the line to actually do it though.

Part of the challenge is finding an electrician willing to work like a sysadmin and do things because they know how they work, rather than only doing things they've explicitly been taught as in line with (dated) regulations.

> Wouldn't the charge / discharge cycles reduce the life of the car battery?

While I'd presume the answer here is "yes", I'd also presume we're talking like a fraction of the vehicle's lifetime charge cycles. Like, (generously/conservatively) 20 to 40 cycles total over the life of the vehicle, no? How often would you estimate your power going out?

For something you (hopefully) don't have to do that often, it seems negligible. But if you're charging and discharging the car daily to do arbitrage you might eventually notice the degradation

I know someone that did this with an old Prius. No software hacking required. Just leave the ignition on, and wire into the high-voltage system (not at the same time, of course!). The engine auto-starts when the battery gets too low.

The more interesting approach is to do it with a used EV. You can get a 100-133 kWh car used for $20-30K. The last time I checked, that was below the price of a house backup battery with a quarter the capacity.

Be sure to alert the fire department ahead of time.

LiFePO4 are much more robust against thermal runaway, omit a lot of the expensive materials that are in typical Li-NMC batteries, and have a better cycle life. They still can't be charged below 0°C, they have worse specific energy, and they generally can't handle the same peak power output, but they're a better choice for fixed storage applications IMO.

there are several devices that allow for 4kw+ to be pulled out of the NACS port, it tricks the car into thinking its CCS charging. Google "tesla v2h" or "tesla discharge device"