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What a year of solar and batteries saved us in 2025

scotthelme.co.uk

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Re: What a year of solar and batteries saved us in 2025

#351
post #332
post #331

Earlier quoted context omitted.

Ok lol...so it turns out you're not even correct on a powerwall's spec...each inverter maxes out at 48A/240VAC...LMAO Be gone troll. https://energylibrary.tesla.com/docs/Public/EnergyStorage/Po...

Yes, 48 amps at 240 is 11.5kw. Each Powerwall 3 is 11.5kw(edit: not to be confused with its capacity which is 13.5 kwh, one is a power output, one is a storage capacity. Just so you don't go thinking that's some amazing mixup between the comments). The original comment is all within your framework of 3 Powerwalls vs one EG4 18K with 3 batteries. That's 12kw AC for the EG4, and 34.5kw on 3 Powerwalls. I've never state…

You keep throwing out specifications without understanding their real life installation use cases and then go as far as to make claims like "EG4 support is bad for DIY'r" which is so far from the truth it's hard to take anything you say seriously. There are hundreds of thousands of forums and YouTube videos from DIY who rave about EG4. In fact Sol-ark has a sketchy support track record (source - several installers I work with)

> The original comment is all within your framework of 3 Powerwalls vs one EG4 18K with 3 batteries. That's 12kw AC for the EG4, and 34.5kw on 3 Powerwalls.

And for the last time, you do not need 34.5kW continuous AC output for a house that is averaging 2 kW per hour per day. Yes, they have two EVs, but also these do not need to charge at their full potential if you plug them in every night. The author isn't generating enough energy from solar of their battery bank so it's pulling from the grid anyway for those loads, so a grid bypass (which EG4 supports up to 200A) means you don't need the inverter to pump out 34.5 kW to loads anyway.

The thing you keep glossing over is that the fundamental problem with a powerwall for scaling systems is that each battery bank you purchase requires you to purchase a built in inverter. The same nearly identical system from EG4 is an 18k + 15 kWh battery which costs $8k, and powerwalls cost $12k+. Thats a 50% premium to get you 185 LRA but 8 kWh less capacity. For an extra $250 you get an AC soft start and a 185 LRA is completed unnecessary and irrelevant.

> Yes, 48 amps at 240 is 11.5kw.

You keep saying these things like I don't understand the math.

> You don't know how to use an amp clamp and don't understand the American split phase power grid.

Lol. And you don't even understand that specifications ratings because they very explicitly say the amps at VAC ratings (120/240) because while it's entirely possible to reach the full potential of wattage... in real life, it's unlikely you will due to how split phase works with inverters. Inverters are rated by amps per leg because your loads on one 120v leg could be higher than the other one (unless all of your loads are 240v in which you would always be using the same amps on both legs).

So to conclude:

1. An identical system is $53k (Powerwall) versus $31k (EG4), which is still hilariously overpriced.

The only measurable differences are:

EG4 gets 6 more continuous AC amps (up to 1.44 kW more)

Powerwall gets much higher surge capacity (555A vs 195A)

EG4 gets 8 kWh more capacity

2. If you need more than 195A surge, you put a soft start in or just let the inverter bypass temporarily to grid.

3. You would never size this system with 3 inverters for someone averaging 48 kWh/day, so the author spent £7k on an additional battery and got an unnecessary inverter purchase which is now directly eating into his ROI.

Re: What a year of solar and batteries saved us in 2025

#352
post #351
post #332

Earlier quoted context omitted.

Yes, 48 amps at 240 is 11.5kw. Each Powerwall 3 is 11.5kw(edit: not to be confused with its capacity which is 13.5 kwh, one is a power output, one is a storage capacity. Just so you don't go thinking that's some amazing mixup between the comments). The original comment is all within your framework of 3 Powerwalls vs one EG4 18K with 3 batteries. That's 12kw AC for the EG4, and 34.5kw on 3 Powerwalls. I've never state…

You keep throwing out specifications without understanding their real life installation use cases and then go as far as to make claims like "EG4 support is bad for DIY'r" which is so far from the truth it's hard to take anything you say seriously. There are hundreds of thousands of forums and YouTube videos from DIY who rave about EG4. In fact Sol-ark has a sketchy support track record (source - several installers I…

>You keep throwing out specifications... >And for the last time...

Well, neither of these are relevant to my original comment. I never commented on the value prop of the original install, only that your comparison in pricing is just not accurate as one is much more capable. Yes, lots of people want 34kw of standing load, because they want to ensure the offset of their HVAC unit. Generally people getting these systems have ridiculous homes, I've worked on a home with 3 20kw diesel generators. I've worked on a home with a seperate 200 amp service just for their pool side projector TV. Just because someone's wants aren't reasonable doesn't mean they don't want it.

>There are hundreds of thousands of forums and YouTube videos from DIY who rave about EG4.

EG4 sucks to try to pry anything out of. I don't actually like Sol-Ark that much either, but they're better to deal with and a better deal. Best deal is just to get an SRNE or similar straight from the source. Again, I paid $800 for my SRNE. I could get a second and parallel it and be outperforming the EG4 for a $3,400 discount. Youtubers are youtubers, not a source of truth. All those same youtubers shill battle born, too...

>Lol. And you don't even understand that specifications ratings because they very explicitly say the amps...

I'm not the one that has conflated two 50 amp phases with a 100 amp service. That's a 50 amp service. 12kw is 12kw. I keep repeating the math because you clearly keep misunderstanding it. A small electric range is typically on a 240 50 amp circuit, incredibly common in most households, and that's a small one.

>Identical system.

How is this identical? $5K for all other labor and materials? How much you paying per foot for the Class K to parallel the batteries? What's the homerun distance on the PV? Your AHJ require metal conduit on the DC runs inside the attic? Shit, if they require a 3R lockable lever disco that's $900 right there before fuses. What you penetrating with? What racking system you using? Shingle or metal roof? If shingle you doing the labor to pull shingles and put in flashing or you hacking it up with some HUGS/RT Minis? What's your max span between mounts given the wind load? S-5!s and HUGs add up fast when you can't get away with a large span. What's your interlock method? If you're landing in the MSP are you derating the mainbreaker? You value your time so little after all that material that you're still under $5k?

Edit: Also, you're gonna be paying a whole lot for LTL on that partial pallet of panels and 14' (if you get the short stuff) racking.

Re: What a year of solar and batteries saved us in 2025

#353
post #239

Earlier quoted context omitted.

People need to stop using the old Mac Pros for home servers, jeez.

I had a old, cheap, used Dell R710 that I bought used in ~2016 until 2025. It only took a few months of running a new, much more efficient server to pay for its self.

My EliteDesk G4 idles at 11W with 4 drives, so it’s not too bad. I really wish we could get something cooler, but it does the job beautifully. I see 150+ for the Dell, ouch.

Re: What a year of solar and batteries saved us in 2025

#354
post #235

Earlier quoted context omitted.

My partner works in the field and we once talked about this. I think the idea is that individual consumers’ and businesses’ batteries can serve the grid as needed. For example, if your car is fully charged and you don’t need it today, it can top up local needs. So I think the writing isn’t on the wall yet for line price going up, although I’m of course talking of a) Belgium, and b) a future that could go wrong if uti…

That’s how it works for us here in Australia. We have 16Wh of solar and 40KWh of battery, and pay (and receive) wholesale rates for electricity. During the say electricity prices are very low or negative, and we run off the solar and charge the car then. In the evenings when demand is high electricity prices can spike, and our system will automatically sell to the grid then. Sometimes we may need to draw from the gri…

That sounds quite good, but you have a massive installation. Did it pay for itself by now?

Re: What a year of solar and batteries saved us in 2025

#355
post #306
post #50

Earlier quoted context omitted.

> I'm assuming you re-did your roof before you installed In the UK I would expect the roof to be tile, which lasts basically forever unless a storm hits hard enough. I did have to have my panels taken down and refitted, at a cost of well over £1000, because I hadn't bird-proofed underneath them (wasn't suggested by original installer). So watch out for that one.

How do you bird-proof them?

Fitting blocks (basically shaped plastic) around the edge to prevent birds from getting underneath and nesting. Merely landing on the panels isn't a huge nuisance, but nesting is.

Re: What a year of solar and batteries saved us in 2025

#356
post #350

Earlier quoted context omitted.

Then pay one to inspect it and sign off for you.

Theoretically a good choice, but where I live, just doesn't work. Either they just say "no thanks" or they will be more expensive than letting them do the whole job. I got the "trick" recommended to do the things yourself, then call a certified guy, and say "look, I contracted a guy, I had no idea, he came did everything, but I got a bad vibe, I would like you check the whole installation". But it also does not reall…

It varies for sure but in my case it helps to know people.

Re: What a year of solar and batteries saved us in 2025

#357

Earlier quoted context omitted.

Any idea why swapping didn't pan out for Tesla? My understanding is they are doing that in China.

> Any idea why swapping didn't pan out for Tesla? ~~Two~~ Three things: 1. California changed the rules shortly after Tesla demonstrated their swap station, which practically eliminated the tax credit for battery swap (at the behest of lobbyists for Toyota, who were backing Hydrogen Fuel Cell technology). Specifically, the credit would be prorated by the percent of “fast refueling” sessions a car did, so EVs primaril…

In addition to all of that, it just doesn't outcompete recharging in the end.

Even if the swap station got to where it was hoped (no reservation needed, automated, drive in, swap, drive out), you'd have a choice between a ~5 minute stop at a swap station, or a ~10-20 minute stop at a charging station. The swap station is always going to be more expensive since it's inherently more complicated, so you're spending more to save a few minutes. And when you stop at the swap station you can go answer the call of nature and grab a snack while you wait. If you want to do either of those anyway, then visiting the swap station means you'll do the swap, then go do those other things, and probably not save any time at all.

Charging time just isn't that much of an issue at this point. I've been driving a Tesla for a decade at this point, with thousands of miles of road trips around the eastern US, and I've never found myself wishing for battery swap infrastructure. Newer cars charge much faster than mine does, too.

Re: What a year of solar and batteries saved us in 2025

#358

Earlier quoted context omitted.

Your link does not support the idea of a supply deficit, at least that I see. Propel panicked about lithium under supply, prices surged and didn't even affect battery prices much, and now we are in oversuppply. The worst that can happen is lag time between demand increase and supply match, and there are substitutes for all key metals for most applications, even copper. Every country will have to figure out how to sup…

Regarding the IEA report; I think you didn't read it carefully enough. In the near term there is no supply deficit (although current price development would seem to beg to differ) - but the point was in an electrification scenario there _would be_ in the 2030s. Given it takes many years to start up mines (as far as I know), that is the issue. For copper - the report is very clear that there already is an issue, which…

I read through the IEA document when it came out, and didn't find anything like what you say, because I remember people claiming things like you say and I couldn't find anything that supported it. If you have quotes, pages, etc. please point to them. The closest contention is also in the summary:

> For lithium, near-term markets appear well-supplied, but rapidly growing demand is expected to push the market into deficit by the 2030s

We've been pushed into lithium supply deficit in the past, and quickly got out of it. This is not a statement that there's not enough lithium or copper, rather that the market wants more than they currently see in development. The IEA document doesn't say anything about electrification not being possible, it's meant as a signal to policy makers to ensure that new copper mines can open up in the future, and that there's great opportunity for countries that do that.

When people are making 100 billion dollar bets on factories that use copper as an input, they are also ensuring their supply years out, which enables development of the necessary mines.

Say the worst case predictions from the document come true: there's a price spike in copper due to there being greater demand than supply. That drives up prices, which spurs on more copper mine development, but the existing copper is still being used to make the energy transition. The electrification trend continues, but just at the rate of current copper extraction! Clever people find substitutions for the electrification challenge. Or people substitute inferior and more expensive non-electrified traditional industry rather than the new tech.

There's a fundamental difference between metals for infrastructure and fuels like oil: if you have a fuel supply shortage it causes inflation, economic contraction, etc. With a shortage of copper and increase in prices in devices that use it, people wait a bit to replace that old appliance (maybe), or use an alternative that perhaps requires fossil fuels.

> Most grids aren't built that way anyway. The residential units are sinks, not sources. In Sweden we don't even have much solar power but already there have been policies aimed at reducing grid exports from residential units, because they are mostly redundant and even harmful.

Grid engineers are extremely conservative, and don't want to learn anything new, and always resist at first. Until somebody shows them how it works, they claim it's impossible. That allowing individual homes to feed back to neighbors will break everything. Then people do it and its fine. Then grid engineers claim that at 1-2% of variable supply the whole grid will come down. Then 1-2% of supply is variable solar and everything is great, so the engineers claim that 5% is the new limit. Or 10%. Or 30%. They are living in the past, don't want to learn anything new, and assume that anything new is impossible. It's a natural feeling for engineers that should be very conservative, but also incorrect. They complain about needing inertia, reactive power, without realizing that all that is quite possible with existing tech! Until a proper cost analysis is done by independent people that are fully honest about the costs, I wouldn't trust anybody saying that allowing a home to feed back into the grid is harmful. Plus, batteries negate the need to feed back into the grid at all. Keep homes as 100% sinks, just pulling down electricity far less. Or put batteries in homes to reduce their peak draw from the grid, so that all the rest of the grid can be far cheaper. There's so much potential that gets ignored just because batteries are new tech.

Re: What a year of solar and batteries saved us in 2025

#359
post #105

Earlier quoted context omitted.

Is delivering back to the grid economical in California? Where I'm from people disconnect solar panels on sunny days because it costs them money to return to the grid.

PG&E does net metering, but even at a sub 1:1 rate past your net usage it does not make sense that it costs more to send energy back to the grid

My provider wasn't PG&E, and I don't know if they do the same, but there's a fixed $30/mo service fee for connecting to the grid, regardless of how little power is used, even if its negative.

Re: What a year of solar and batteries saved us in 2025

#360

Earlier quoted context omitted.

But is that rate always positive? Where I'm from during peak sun hours, the rate is negative and you end up paying money to deliver money to the grid. They do this to incentivise you to decouple your solar installation during peak sun hours so the net doesn't get flooded with too much energy.

In CA it can be 0 but not negative. Depending on when you signed up for NEM you may have a guaranteed floor like 4¢/kWh or even much more.

The $30+ minimum on my bill was from a service fee, for connecting to the grid regardless of how little power was used.
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