Una casa fora de xarxa per 13.500 dòlars? Així és el sistema solar DIY
Un creador nord-americà mostra un sistema solar domèstic de 12 kW amb bateries LiFePO4 i 9,6 kWp de panells que, segons ell, pot alimentar la casa per uns 13.500 dòlars. Desglossem què inclou i què queda fora del càlcul.
Una instal·lació barata en comparació amb una oferta de 100.000 dòlars
Minute Man Solar explica que va rebre un pressupost superior als 100.000 dòlars per aconseguir una casa energèticament autosuficient. Després d’una primera instal·lació d’uns 25.000 dòlars, presenta una configuració encara més econòmica que situa al voltant dels 13.500 dòlars si s’equipa amb sis bateries.
El sistema es troba als Estats Units i està adaptat a una xarxa residencial de 120/240 V, connectors NEMA, normes UL i permisos locals. No és un esquema que es pugui copiar directament a Catalunya. Les tensions, els equips homologats, les proteccions i la legalització són diferents. El vídeo és útil per entendre les decisions de disseny i el cost dels components, però les connexions de potència han de quedar en mans d’un professional habilitat.
L’autor diu que pot alimentar aire condicionat, forn elèctric, assecadora i carregar un Rivian R1S. Això descriu els tipus de càrrega que el sistema ha suportat, no prova que pugui fer-les funcionar totes simultàniament ni que mantingui autonomia durant qualsevol setmana d’hivern.
Les tres peces: sortida, emmagatzematge i entrada
El muntatge s’explica amb tres blocs:
- l’inversor converteix l’energia contínua de bateries i panells en corrent altern per a la casa;
- les bateries guarden l’excedent per a la nit o els moments de poca producció;
- els panells fotovoltaics aporten energia i recarreguen l’acumulació.
Aquesta separació ajuda a dimensionar el sistema. La potència de l’inversor determina quines càrregues i pics pot assumir. La capacitat de les bateries determina durant quant temps. La potència solar i el clima decideixen a quina velocitat es recupera l’energia gastada.
EG4 12000XP: 12 kW continus i una sortida intel·ligent
El cor del sistema és un EG4 12000XP, que al vídeo costa uns 1.900 dòlars. La documentació del fabricant especifica 12.000 W continus per al model mostrat, dos seguidors MPPT i fins a 24.000 W de potència fotovoltaica utilitzable. També disposa d’una capacitat de pic limitada en el temps i admet bateries de 48 V.
L’autor valora especialment la sortida Smart Load. Es pot programar perquè una càrrega no prioritària —posa l’exemple d’un miner de Bitcoin— només rebi energia quan les bateries ja estan prou carregades i la casa està coberta. És una manera pràctica d’utilitzar excedents sense comprometre serveis essencials.
La sortida de la casa es porta a un connector de 50 A i a una entrada de generador, amb un interbloqueig mecànic al quadre que impedeix connectar alhora la xarxa i la font alternativa. Aquest detall és crític: alimentar una instal·lació a través d’una entrada sense una commutació segura pot enviar tensió cap a la xarxa i posar en perill tècnics i equips.
El manual d’EG4 demana proteccions, seccionament, seccions de cable i parells de connexió concrets. Els diagrames del fabricant indiquen expressament que el disseny final l’ha de fer un professional autoritzat i l’ha d’aprovar l’autoritat competent.
Bateries de servidor: el principal estalvi i el principal risc
La part més cara és l’acumulació. El pressupost de 13.500 dòlars assumeix sis bateries LiFePO4 de 48 V i 100 Ah, aproximadament 5,12 kWh nominals per unitat. En conjunt serien prop de 30,7 kWh nominals abans de considerar profunditat de descàrrega, pèrdues i reserves del sistema. Durant la demostració, però, l’autor afirma que només està utilitzant tres unitats del model nou.
Les bateries es comuniquen amb l’inversor per CAN en bucle tancat. Això permet que l’inversor rebi del BMS l’estat de càrrega i els límits reals, en lloc d’estimar-los únicament a partir del voltatge. El manual d’EG4 recomana precisament aquesta comunicació amb bateries de liti compatibles i una capacitat mínima de 400 Ah per assolir les especificacions completes de sortida.
El creador escull bateries més econòmiques que no estan llistades per UL. Segons ell, això li estalvia uns 700 dòlars per unitat, però li impedeix utilitzar la configuració concreta en què l’inversor pren automàticament energia de la xarxa. Per a aquesta opció recomana una bateria certificada.
La diferència entre «bons components» i un sistema certificat és important. UL explica que, als Estats Units, els codis residencials poden exigir que el conjunt d’emmagatzematge compleixi UL 9540, no només que una bateria individual sembli equivalent a una de certificada. La certificació avalua bateries, inversor, proteccions i control com a sistema.
El vídeo inclou una advertència involuntària molt clara. L’autor connecta inicialment cables de polaritat invertida i explica que les proteccions del BMS i de l’inversor van evitar danys. Que no hi hagués un accident no converteix l’error en segur: un banc de 48 V amb milers d’amperes potencials de curtcircuit pot provocar arcs, incendi i lesions greus.
24 panells a terra: 9,6 kWp sense pujar a la teulada
La instal·lació utilitza 24 panells bifacials de 400 W, és a dir, 9,6 kWp nominals. L’autor diu que els va trobar per uns 100 dòlars cadascun i recomana mirar el mercat local per evitar costos d’enviament. Els col·loca sobre suports ajustables a terra, una solució que facilita canviar la inclinació i evita treballar a la teulada.
L’argument econòmic és que una instal·lació sobre coberta als Estats Units li exigiria permisos estructurals i elèctrics, inspecció i dispositius de desconnexió ràpida. Els seus suports són un producte propi i afirma que han resistit vents de 70 milles per hora, però també diu que no estan pensats com una instal·lació exterior permanent. Aquestes dues afirmacions no substitueixen un càlcul estructural, ancoratges adequats ni les càrregues locals de vent i neu.
Posar panells a terra tampoc elimina automàticament els permisos. L’obra, la distància a límits, el cablejat enterrat, la posada a terra i l’impacte urbanístic depenen del municipi i de la normativa aplicable.
Com aconsegueix engegar l’aire condicionat
Un compressor pot demanar un pic molt superior al consum estable. El creador instal·la un Micro-Air EasyStart Flex i afirma que redueix el corrent d’arrencada de 120 A a uns 34 A, per sota de 9 kW en el seu cas. El fabricant anuncia reduccions de fins al 75%, però el resultat depèn de la unitat i de la instal·lació.
Durant la prova, el monitor mostra aproximadament 4,2 kW per al conjunt de la casa amb l’aire condicionat en marxa: uns 1,6 kW arriben dels panells al vespre i 2,7 kW de les bateries. És una fotografia d’un moment concret, no un balanç energètic anual.
Per saber si el sistema és realment autònom caldrien dades de diversos mesos: consum diari, pitjor setmana solar, temperatura, pèrdues, degradació, profunditat de descàrrega i hores sense sol. Un únic rebut elèctric gairebé buit tampoc demostra que no caldrà xarxa o generador a l’hivern.
Què inclou i què pot faltar als 13.500 dòlars
El vídeo permet identificar part del pressupost:
- inversor d’uns 1.900 dòlars;
- sis bateries d’uns 770 dòlars cadascuna;
- 24 panells d’uns 100 dòlars;
- armari de bateries d’uns 750 dòlars, que es podria substituir per una base més simple;
- arrencador suau d’uns 400 dòlars;
- suports, cablejat, connectors, proteccions, entrada de generador i petit permís.
No hi ha un full de costos complet auditat. Poden quedar fora impostos, enviament, eines, mà d’obra pròpia, paisatgisme, excavació, enginyeria, assegurança, inspeccions i futures substitucions. El pressupost comercial de 100.000 dòlars tampoc es pot comparar directament sense saber potència, garanties, muntatge, finançament i serveis que incloïa.
La xifra és plausible com a cost de materials comprats amb molta recerca i feina pròpia, però no com a preu universal d’una instal·lació legalitzada i entregada clau en mà.
Què canviaria a Catalunya
A Espanya, una instal·lació domèstica ha de complir el Reglament electrotècnic per a baixa tensió, les seves instruccions tècniques i les normes aplicables als sistemes fotovoltaics. Si hi ha connexió amb la xarxa, també entra en joc el Reial decret 244/2019 i les exigències de protecció, antiabocament quan correspongui i documentació de posada en servei.
L’Institut Català d’Energia recorda que la tramitació té un nivell municipal abans de l’obra i un nivell energètic, i que les instal·lacions poden incorporar bateries o carregar un vehicle elèctric. La intervenció administrativa pot simplificar-se amb comunicació prèvia, però no desapareixen el projecte o memòria, el certificat i les proteccions necessàries.
Els connectors NEMA, el sistema 120/240 V i les referències UL del vídeo són nord-americans. A Catalunya cal seleccionar inversor, bateries, quadres i proteccions conformes al mercat europeu i compatibles entre ells. Una entrada de generador improvisada o un interbloqueig dissenyat per a un altre quadre no són equivalents acceptables.
La idea que sí que es pot traslladar
La lliçó útil no és copiar el cablejat. És dividir el problema en potència, energia i generació; mesurar els pics; prioritzar càrregues; i comparar el cost de l’autonomia total amb alternatives com autoconsum connectat a xarxa, una bateria més petita o suport d’un generador.
El sistema del vídeo mostra fins on pot arribar una persona experta comprant components directament. També mostra per què l’estalvi depèn d’assumir feina, risc i manteniment que una empresa instal·ladora incorpora al preu. Abans de decidir, cal dimensionar amb consums reals i fer revisar el projecte per un instal·lador autoritzat.
Contrast i context
Fonts consultades
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01
EG4 Electronics EG4 12000XP — manual
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02
EG4 Electronics EG4 12000XP — System Wiring Diagrams
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03
Micro-Air EasyStart Flex Home AC Soft Starter
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05
Boletín Oficial del Estado Reglament electrotècnic per a baixa tensió
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06
Boletín Oficial del Estado Reial decret 244/2019 sobre autoconsum
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07
Institut Català d'Energia Preguntes freqüents sobre autoconsum
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08
Institut Català d'Energia Autoconsum fotovoltaic domèstic: consells i bones pràctiques
Font de treball
Transcripció amb marques de temps
Consulta la transcripció
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0:00
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Electricity prices are going up like crazy, and I wanted to be 100% self-reliant with my electricity. So, I got a quote to get solar on my house so that I could have that, and it was over $100,000. But, in a recent video that I did, I showed you how I was able to do that for 1/4 of the cost at only $25,000, and that's being 100% self-reliant. But, in this video, I'm going to cut that again in half. So, it's going to be about 1/8 of the cost of what the solar company quoted in order to be completely self-reliant. With this setup, I'm able to run my air conditioner cuz now it's hot out. I'm also able to charge my electric vehicle, which is a Rivian R1S Max Pack, which has the biggest battery pack of the Rivian SUVs. I have two washers and dryers. One of them is electric, and the other one is gas. I'm able to run both of these as well. And the last really big load that I have in my house is my oven because it, too, is electric. So, I'm going to go over exactly what components I'm using that are really good quality in order to have reliable, self-sufficient energy. But, in addition to that, I'm going to show you another way where you can save even more money on this exact setup. None of this is illegal. It's perfectly fine to do. You should always consult with an electrician to make sure you're doing everything safe. There's only one really small permit that I pulled just to be able to get the connection from the solar setup into my house. I'm going to show you exactly how I did it.
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1:12
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A solar system is made up of three parts. That's the output, the storage, and the input. The output is the inverter. The storage are the batteries, and then the input is the solar. I like the 12000XP in general because it's a very good price at only $1,900 right now, but it also has some amazing features that pretty much no other inverter of the same capacity have. That extra special feature is this breaker right here. You might be able to see it, but under here it says smart load. Let's say that I want to run my Bitcoin miner only once the batteries are full and all of the house is already taken care of. That way, my Bitcoin mining doesn't take away from my house having electricity. I can set up my own outlet that sticks out the the of this, and I plug my Bitcoin miner into that. Now, only when I have excess will the Bitcoin miner run, and it will automatically shut off based on the parameters that I put in the inverter here. One of the other things that I really, really like are how many solar inputs there are, and being able to have up to 24,000 W of solar input is absolutely insane. And this is actually far easier to wire than you would expect. Pretty much any novice can do that. So, let me show you all that's required to get this up and running to run my whole house. We'll start with the output. You can see this breaker here, right behind here, it says load. So, I have my leg one as my black and my leg two as my red, and this is just six-gauge wire. You could bump it up to four-gauge wire if you wanted to be extra safe, but six-gauge is rated for this amount of power. You'll see that the white comes up and it goes to this big bus bar right here in the back. That is the neutral bus bar, and then the ground wire comes around and goes over here to the grounding bus bar. The main thing here that's really important is that your AC output is properly rated. You can't tell right now because I have this big plug in here, but they call this a four-square box. It's just a metal box I picked up from Home Depot, but I got an EV or electric vehicle rated NEMA 14-50R connection right here because that is the connector that's actually capable of running 12,000 W constantly and not melting. Originally, I had just taken this cable and these wires and wired it directly into here, and that was working fine, and then I realized that's really unsafe. And ironically, these cost about the same, so you might as well go with this. I'll have links down below to what I bought. Now, if I do want to charge from a generator, I have this NEMA 14-50P. It's P cuz it's a plug or it has prongs wired in to the grid input. You can see I still have black as my leg one and red as my leg two. The white goes over to the neutral bar, and then the green over to the ground bar. For the battery input, these are actually one aught cables because that was the thickest I could get that have these SB175 connectors on them. And so, I've wired those directly into this bus bar here for the battery, and now I actually have a quick disconnect from the whole battery bank. So, if I want to use this inverter with a different battery bank or these batteries with another inverter, this gives me that capability by having this quick disconnect. And just like I mentioned with the solar input, I just made two sets of wires coming out each one of these and they're going into each PV input. If this is at least your second time on the channel, hopefully that means you'll subscribe because you're finding this information helpful. And if you've made it this far in the video, then hopefully you'll smash the like button as well. But all of the links to everything that I'm using are going to be in the description and the first comment down below. So, that's the inverter and that's the AC output.
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4:39
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But I want to get into what's the most expensive part of the entire system, and that is the battery setup. There's a trick with the batteries and that is that you either have to choose to be UL listed certified or not UL listed. There are many non-UL listed batteries that are UL quality. They simply have not gone through the UL certification process and therefore cannot work in conjunction with the grid. This inverter has the ability to have a dedicated grid input. So, that way if your battery and solar system dies, say at 3:00 in the morning after it's drained for some reason, it will automatically kick back to grid power. And then once the solar recharges the batteries, it will switch back to off-grid power. And if you're going to do a setup like that, you must use UL listed batteries. I'm not doing that setup here and so using these more affordable batteries that are still very high quality, I was able to save like $700 per battery and that makes a huge difference. The first thing I want to point out is this battery rack. I bought this from SunGold and I really like it. You have to assemble it. That part super sucks. But for $750 or so, you get this whole enclosure and you can fit pretty much any battery. Now, you may have seen my other video where I tested these Humless batteries and they're good, but I think I might have actually found a better one. And those are the Tech X batteries. These are the same price as the Humless or cheaper, but now you actually get a screen with the ability to adjust all of the communications so that way you can get it to work with pretty much any inverter. So, for example here, I can go into the RS485 connection, which is this one here, or the CAN bus connection. I have found that for the 12,000 XP, I have to use the CAN connection in order to get what's called closed loop communication. That just means that you actually get to see the battery percentage on the screen and in the app. Whereas, if you're using open loop communication, you're just using the voltage of these batteries to determine roughly what state of charge the batteries are at. So, I made a mistake early on with these cables. I got myself backwards because I saw ah, these red cables over here from these other batteries. And so, obviously, this was already my positive bus bar, but on these batteries, the black or the negative is actually on the right side. So, I had originally connected these black cables to the positive bus bar, and luckily, because of all the BMS protection in these, it didn't cause a problem at all. Same with the inverter, there was no issue when I made the mistake. And I didn't like how long the cables were that came with the batteries at first. And so, I shortened them and cut them down to my own size so that this was going to be nice and clean. And then in the end, I realized that I did have to jump from the left side all the way to the right side. And so, what I did is I bought these four gauge rated Polaris taps. A Polaris tap is just a way to take a thick cable and join it together. So, I ended up putting the cables back together. You might as well just leave them how long they come. And the short communication cable that comes with the batteries wasn't long enough for me because of how I set up this server rack. Technically speaking, I could actually fit seven batteries in here because these batteries are not really tall. Some of the other batteries that I've used were really tall and pretty much don't work with any other rack, and that's a huge frustration. These are actually quite short, and so I have tons of airflow through here, so I'm not worried about overheating at all. But, I did have to get longer communication cables, and I just bought these. They're like a couple of dollars each on Amazon. So, currently these batteries are about $770 each, and if there are coupons that I have for it, they'll be linked down below. But, you can see here, these are the dip switches, and you just follow the user manual to tell you what position to put these in so that way these can have proper communication. But, then here you have a state of charge indicator, and then if there's an issue like miscommunication, this alarm light will start flashing. This is the breaker to turn on the whole system, and then this power button will control all of the units. Once they've all been programmed together, you just have one power button for the whole system. Probably the biggest thing to know with these communication cables is that from top down, you actually start in communication port B, and then you come down to port A, and then B to A, and so on. There are two other really nice things that I really like about these TechEx batteries more than pretty much any other battery right now. And the first one is that they also include these cable whips, and these are to be used if you're not using a third-party server rack. But, you can actually take this whip and connect between two batteries, and you just keep stacking all the way up, and you can make one big massive battery pack by using these parallel cables. So, these come with every battery in addition to the really long wires. So, you have both options in the box at no extra cost. But, in addition to that, they include these special brackets, and these clamp onto the side of the TechEx batteries. But, what's cool is they have these little index points, so you can actually stack the batteries directly on top of each other. So, if you just went to Harbor Freight and got one of the 1,000-lb rated furniture dollies. They're like $30. You could put six batteries all on top of that using these and have your own mobile battery setup that's going to be super compact. And if you just went with this option, which is already included, you wouldn't have to buy this $750 rack. So, just another way that TechX is helping this whole system be more affordable. Now, these Humless batteries are not turned on right now. I am not using them in conjunction with the TechX. This test has all been done with the TechX batteries and they have worked phenomenally with zero issues at all. I've had zero heat issues, zero communication issues except for when I was doing RS485. As long as you use the CAN communication, then it works great. I can't recommend these batteries enough, but they're not UL listed. So, if you're going to do the grid-tied setup where the grid automatically takes over, you're definitely going to have to look for another battery and I'll put my recommendation down below. I can see that my battery is at 100% state of charge. If I didn't have the communication, I would just have to look at this voltage and personally know that at 54.6 V that this is actually full.
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10:43
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Now, getting onto the third part, solar is the lifeblood of the whole system. Now, in this case, I've got 24 400-W bifacial solar panels. I really, really like these. I found these super cheap for about $100 each and there are better ones that are 450 W each and actually have a lower voltage. But, you really should just be checking Facebook Marketplace and see if you can get some bifacial 400 to 450 W panels for really cheap locally. Now is actually an amazing time to get solar because these panels have never been cheaper. But then, the next trickiest thing is where do you put the solar panels? Cuz if you put them up on the roof, you have to get both a structural permit as well as an electrical permit and then you also have to get it inspected and use rapid shutdown devices like DC optimizers on these in order to be able to use them on your roof. I didn't want to go through that hassle cuz I'm trying to do this as affordably as possible. So, that's why I have everything mounted on the patent pending Minute Man Solar Portable Panel Stands. These stands are actually not intended to be used forever outside, but the materials used and everything that's all a part of this is actually rated to 25 years of constant outdoor use. And you can see my yard is not flat. I got weeds growing everywhere. It is a total mess. That's cuz we moved into this house like 6 or 7 months ago and it didn't come with a yard. So, I still have to do all of the landscaping on this. And so, in the meantime, having these fully adjustable stands makes it really easy to work on pretty much any terrain. When you get the Minute Man Solar Stands, you get what I call the upper legs. And if you get that, then the bottom edge of the panel just rests on the ground. But because I've got so many weeds here and because I'm in Idaho where I get snow during the winter, I added the lower legs. So, that way if it snows, the snow will fall off the front. If there's weeds growing, I have plenty of room before the weeds start to cover the panels. On average, 75% of people who order the panel stands add the lower legs because they don't want to have to worry about dirt and leaves and snow building up on the bottom of the panel. This H bracket here is one of the newest additions. Every kit is now including these. And when you put all of these together, it becomes super strong. But you see that weather station right there? I specifically put that in for one main reason. And that's for getting tracking on what kind of wind these solar panels have gone through. You'll notice these panels here don't even have the H bar on them because this was the older model and I've just not upgraded them. And these have gone through 70 mile an hour winds where the wind was coming from this direction, the worst case scenario. And I've not adjusted these since I installed these months ago. And the front row was actually at my old house running that. So, they've been in operation for more than a year non-stop.
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13:24
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From the inverter, we're going to this EV outlet and I have it on this NEMA 14-50P to SS250R cable that runs across my garage and then comes into this generator inlet port. This was like 30 or 40 bucks off Amazon, and this is the SS250R connection. It's twist locked into here, and I ran a six gauge cable going from this inlet all the way through my attic into my basement. And then inside of my electrical panel, I installed this small device here, which is called an interlock kit. Every electrical panel is going to be a little bit different, so you do have to find the kit that's specific to your panel. Mine's a Square D, so I got a Square D interlock, but you can see that my grid power is in the off position, and this 50 amp breaker is in the on position. So, the 12,000 XP system is running right into here and now supplying power to both of these electrical panels, and over here is my EV charger. I'm able to run 100% of everything just fine, and I specifically turned off the air conditioner to show you that I can turn and run it without a problem. And there's one trick to do this that will make it work with this system. So, I'll show you that here, but right now the system is off. I'm going to go ahead and turn it on. I don't know if you can hear the background noise, but the handler's actually right behind you, and so we are now blowing cold air. And because I'm doing closed loop communication with the TechX batteries, I can see exactly what's going on here. So, I can see that entirely the whole house is pulling about 4,200 W. From the batteries, it's pulling 2,700, and from the solar, it's pulling about 1,600. And that makes sense cuz it's almost 6:00 in the evening. But the reason that this works so well is because I'm using a MicroAir Flex AC soft start device. This unit right here, I tied into four different wires. I just took the orange wire to the herm on the capacitor, and then I took the black wire and put it on top of where the black connection is on the switch, and then I spliced into this yellow wire that goes from the switch all the way to the compressor inside the air conditioner. And so, I spliced on this white wire and this brown wire onto that yellow wire, and now I went from 120 amps of starting power all the way down to about 34 amps, which is just under 9,000 W. So, that makes it really easy to stay within the surge capacity of the 12,000 XP inverter, allowing me to run my air conditioner. So, I paid about $400 for that MicroAir device. It's worth every penny.
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16:09
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So, this entire system is only about $13,500 if you get six of these batteries. I'm actually only running three of them right now, but I really wish I had three more of these because I like these a lot better than any of the other server batteries I've tested, especially for the non-UL listed kind. They're literally the cheapest ones that I can find right now, and they are not cheaping out on quality. This is my live bill right now from Rocky Mountain Power, and you can see for the last few days it's not fully updated, and I don't know why there are any bars here cuz I have not been pulling any power from the grid, but you can see how this has completely dropped off by using this setup. I would say that if you don't have an electric vehicle, and if your house doesn't use any electrical heat, such as the water heater, the dryer, the oven, and so on, if that's all propane or natural gas, you can actually probably get away with just a 6,000 XP, but surprisingly the 12,000 XP is not much more in cost, and you get way bigger benefits with more solar as well as having bigger battery input, and especially the smart load. So, there's not really a reason to spend $100,000 from a solar company to have this kind of dependability unless you don't want to do any of the work, at which point definitely go with them. And if this seems too complicated and you want something even simpler, that's why I made this video, so that way you can still go off-grid completely affordably. So, that's the decision that you'll have to make on which system's the right for you. I definitely really like this setup, and I want to get a lot more of these Tech X batteries because they're so good. Then, comment down below which way you think you would do this.