I set up my own home network with a Vertiv Liebert Li-ion UPS a few years ago and was thinking about how inefficient the whole process is regarding power. The current goes from AC to DC back to AC back to DC. Straight from the UPS as DC would work much better, and as I was teaching myself more about networking equipment, I was surprised to learn that most of it isn't DC input by default (i.e., each piece of equipment tends to come with built-in AC-DC conversion).
Then I started routing ethernet with PoE throughout my house and observed that other than a few large appliances, the majority of powered devices in a typical home in 2026 could be supplied via PoE DC current as well! Lighting, laptops, small/medium televisions. The current PoE spec allows up to 100 W, which covers like 80% of the powered devices in most homes. I think it would make more sense to have fewer AC outlets around the modern house and many more terminals for PoE instead (maybe with a more robust connector than RJ45). I wonder what sort of energy efficiency improvements this would yield. No more power bricks all over the place either.
show comments
Animats
800V to each rackmount unit, with hot plugging of rack units? That's scary.
The usual setup at this voltage is that you throw a hulking big switch to cut the power, and that mechanically unlocks the cabinet. But that's not what these people have in mind.
They want hot-plugging of individual rackmount units.
GE has a paper about the power conversion design, but it doesn't mention the unit to rack electrical and mechanical interface. Liteon is working on that, but the animation is rather vague.[2] They hint at hot plugging but hand-wave how the disconnects work.
Delta offers a few more hints.[3] There's a complex hot-plugging control unit to avoid inrush currents on plug-in and arcing on disconnect. This requires active management of the switching silicon carbide MOSFETs.
There ought to be a mechanical disconnect behind this, so that when someone pulls out a rackmount unit, a shutter drops behind it to protect people from 800V. All these papers are kind of hand-wavey about how the electrical safety works.
Plus, all this is liquid-cooled, and that has to hot-plug, too.
DC power has been an option for datacenter equipment since I was a young lad racking and stacking hardware. Cisco, Dell, HPE, IBM, and countless others all had DC supply options. Same with PDUs. What’s old is new again.
90% of the power in our academic data center goes 13.8kV 3-phase -> 400v 3-phase, and then the machines run directly from one leg to neutral (230v). One transformer step, no UPS losses, and the server power supplies are more efficient at EU voltages.
But what about availability? If you ask most of our users whether they’d prefer 4 9s of availability or 10% more money to spend on CPUs, they choose the CPUs. We asked them.
There are a lot of availability-insensitive workloads in the commercial world, as well, like AI training. What matters in those cases is how much computing you get done by the end of the month, and for a fixed budget a UPS reduces this number.
show comments
bandrami
I stg if I see the kids talk about Westinghouse being batterymogged I'm leaving the Internet
stego-tech
I've been hearing this line for over a decade, now. "Immersion cooling will make data centers scale!" "Converting to DC at the perimeter increases density!"
Yes, of course both of those things are true, and yes, some data centers do engage in those processes for their unique advantages. The issue is that aside from specialty kit designed for that use (like the AWS Outposts with their DC conversion), the rank-and-file kit is still predominantly AC-driven, and that doesn't seem to be changing just yet.
While I'd love to see more DC-flavored kit accessible to the mainstream, it's a chicken-and-egg problem that neither the power vendors (APC, Eaton, etc) or the kit makers (Dell, Cisco, HP, Supermicro, etc) seem to want to take the plunge on first. Until then, this remains a niche-feature for niche-users deal, I wager.
show comments
wolvoleo
Well they're kinda transitioning back. When I grew up most DCs (and telecom facilities) were running on 48V DC. Easy to back up with a big room full of lead acid batteries (just keep an eye on that hydrogen gas lol)
sholladay
Is there anything left in a modern home that really needs or is better on AC?
We have some old ceiling and exhaust fans, but I know those can be replaced. Our refrigerator is AC, but extended family with an off-grid home has a DC refrigerator that cycles way less, probably due to multiple design factors but I’m sure the lack of transformer heat is part of it. I’m not as sure about laundry machine or oven/cooktop options but I believe those are also running on DC in the off-grid home without inverters.
Most of these AC appliances also have transformers in them anyway for the control boards. It seems kind of insane to me that we are still doing things this way.
show comments
neoCrimeLabs
The datacenter I built in 2007 was DC.
Many datacenters I'd been to at that point were already DC.
Didn't think this was that new of a trend in 2026, but also acknowledge I did not visit more than a handful of datacenters since 2007.
It just seemed like a undenyably logical thing to do.
show comments
BorisMelnik
its really wild at all the AC to DC changes. for those non electric engineers / hardware hackers (like myself) one of the biggest "examples" I've seen of this has been ceiling fans.
Installing a ceiling fan used to be treacherous and so heavy. Also loud and buzzy after installed. Now the fans in these things are so lightweight and easy.
seeing the same in many more areas (lighting, etc)
show comments
p0w3n3d
Hard as a rock!
Well it's harder than a rock!
KnuthIsGod
Waiting for home DC.
It is silly to have AC to DC converters in all of my wall connected electronics ( LED bulbs, home controller, computer equipment etc )
show comments
umvi
I don't understand why new houses don't just have one high quality AC/DC converter so you can just use LED lighting without every bulb needing its own AC/DC converter. I imagine the light bulb cartel wouldn't really like that.
show comments
tezza
They were Thunderstruck?
notorandit
It does make a whole lot is sense.
The amount of energy you loose to convert AC to DC can be humongous .
And useless if you produce your own power (normally already in DC).
b00ty4breakfast
They're still converting from AC to DC at the datacenter, it just isn't being stepped down at the perimeter. There is no transmission of HVDC going on. This isn't really Edison's revenge, more like his consolation price, ha!
amluto
I wonder how much of the benefit is simpler redundant power equipment. For AC, you have standby UPSes and line-interactive UPSes and frequency and phase synchronization. And everything needs a bit more hold-up time because, in case of failure, your new power supply might be at a zero crossing.
For 800V DC, a simple UPS could interface with the main supply using just a pair of (large) diodes, and a more complex and more efficient one could use some fancy solid state switches, but there’s no need for anything as complex as a line-interactive AC UPS.
adrr
Our houses should be DC. So wasteful to have all these bricks to change to AC to DC.
show comments
gwbas1c
Anyone notice that 400V and 800V are also used in EV battery architecture? I wonder if there's any sharing of technology?
everdrive
"How can we turn this technical story into a story about people and their conflicts?"
sghiassy
I’ve always wondered about these new High-Voltage DC (HVDC) transmission lines.
I always thought AC’s primary benefit was its transmission efficiency??
Would love to learn if anyone knows more about this
show comments
shdudns
How is DC better than a three phase delta 800Vrms, at 400Hz?
- Three conductors vs two, but they can be the next gauge up since the current flows on three conductors
- no significant skin effect at 400Hz -> use speaker wire, lol.
- large voltage/current DC brakers are.. gnarly, and expensive. DC does not like to stop flowing
- The 400Hz distribution industry is massive; the entire aerospace industry runs on it. No need for niche or custom parts.
- 3 phase @ 400Hz is x6 = 2.4kHz. Six diodes will rectify it with almost no relevant amount of ripple (Vmin is 87% of Vmax) and very small caps will smooth it.
As an aside, with three (or more) phase you can use multi-tap transformers and get an arbitrary number of poles. 7 phases at 400Hz -> 5.6kHz. Your PSU is now 14 diodes and a ceramic cap.
- you still get to use step up/down transformers, but at 400Hz they're very small.
- merging power sources is a lot easier (but for the phase angle)
- DC-DC converters are great, but you're not going to beat a transformer in efficiency or reliability
show comments
Aloisius
This article seems to imply that 800V DC is high-voltage DC, but that seems quite low.
show comments
skullone
Transitioning? It already happened decades ago. Only smaller scale/generic or less proficient "we bought all Dell and HP" use AC. At large scale it's been a ton of DC for literally decades. And for 70 years in telco and network gear.
tibbydudeza
Have a solar system at home and from the panels it is DC into the batteries but then the inverter needs to convert it to 220V/50Hz AC for home use.
flossly
AC is also waaaay safer for households: since the power drop to to zero 100x (50Hz) per second switches are cheaper and safer, and electrocution is less likely to happen.
saltyoldman
The large brick you have on all your tech when you plug it in is the converter. AC works great for some applications, none of them really technical in nature.
hristov
It is absolutely stupid to talk about this as edisons revenge. If Tesla had the modern high power transistors needed to get high voltage dc out of the ac produced from a spinning turbine he would be all for high voltage dc too. Tesla understood that high voltage was needed for efficient long range transmission. He also understood that transformers were the inly remotely efficient way to climb up to and down from these high voltages. And transformers only work with ac. So he designed an ac system and even designed some better transformers for it.
If there was anything like a high power transistor back then he would have used that. High power transistors that are robust enough to handle the grid were designed inly recently over 100 years after the tesla/edison ac/dc argument.
show comments
fredgrott
That is about like aying the band AC DC had its revenge.....
I set up my own home network with a Vertiv Liebert Li-ion UPS a few years ago and was thinking about how inefficient the whole process is regarding power. The current goes from AC to DC back to AC back to DC. Straight from the UPS as DC would work much better, and as I was teaching myself more about networking equipment, I was surprised to learn that most of it isn't DC input by default (i.e., each piece of equipment tends to come with built-in AC-DC conversion).
Then I started routing ethernet with PoE throughout my house and observed that other than a few large appliances, the majority of powered devices in a typical home in 2026 could be supplied via PoE DC current as well! Lighting, laptops, small/medium televisions. The current PoE spec allows up to 100 W, which covers like 80% of the powered devices in most homes. I think it would make more sense to have fewer AC outlets around the modern house and many more terminals for PoE instead (maybe with a more robust connector than RJ45). I wonder what sort of energy efficiency improvements this would yield. No more power bricks all over the place either.
800V to each rackmount unit, with hot plugging of rack units? That's scary. The usual setup at this voltage is that you throw a hulking big switch to cut the power, and that mechanically unlocks the cabinet. But that's not what these people have in mind. They want hot-plugging of individual rackmount units.
GE has a paper about the power conversion design, but it doesn't mention the unit to rack electrical and mechanical interface. Liteon is working on that, but the animation is rather vague.[2] They hint at hot plugging but hand-wave how the disconnects work. Delta offers a few more hints.[3] There's a complex hot-plugging control unit to avoid inrush currents on plug-in and arcing on disconnect. This requires active management of the switching silicon carbide MOSFETs.
There ought to be a mechanical disconnect behind this, so that when someone pulls out a rackmount unit, a shutter drops behind it to protect people from 800V. All these papers are kind of hand-wavey about how the electrical safety works.
Plus, all this is liquid-cooled, and that has to hot-plug, too.
[1] https://library.grid.gevernova.com/white-papers-case-studies...
[2] https://www.youtube.com/watch?v=CQOreYMhe-M&
[3] https://filecenter.deltaww.com/Products/download/2510/202510...
DC power has been an option for datacenter equipment since I was a young lad racking and stacking hardware. Cisco, Dell, HPE, IBM, and countless others all had DC supply options. Same with PDUs. What’s old is new again.
See e.g. https://www.dell.com/support/kbdoc/en-us/000221234/wiring-in...
90% of the power in our academic data center goes 13.8kV 3-phase -> 400v 3-phase, and then the machines run directly from one leg to neutral (230v). One transformer step, no UPS losses, and the server power supplies are more efficient at EU voltages.
But what about availability? If you ask most of our users whether they’d prefer 4 9s of availability or 10% more money to spend on CPUs, they choose the CPUs. We asked them.
There are a lot of availability-insensitive workloads in the commercial world, as well, like AI training. What matters in those cases is how much computing you get done by the end of the month, and for a fixed budget a UPS reduces this number.
I stg if I see the kids talk about Westinghouse being batterymogged I'm leaving the Internet
I've been hearing this line for over a decade, now. "Immersion cooling will make data centers scale!" "Converting to DC at the perimeter increases density!"
Yes, of course both of those things are true, and yes, some data centers do engage in those processes for their unique advantages. The issue is that aside from specialty kit designed for that use (like the AWS Outposts with their DC conversion), the rank-and-file kit is still predominantly AC-driven, and that doesn't seem to be changing just yet.
While I'd love to see more DC-flavored kit accessible to the mainstream, it's a chicken-and-egg problem that neither the power vendors (APC, Eaton, etc) or the kit makers (Dell, Cisco, HP, Supermicro, etc) seem to want to take the plunge on first. Until then, this remains a niche-feature for niche-users deal, I wager.
Well they're kinda transitioning back. When I grew up most DCs (and telecom facilities) were running on 48V DC. Easy to back up with a big room full of lead acid batteries (just keep an eye on that hydrogen gas lol)
Is there anything left in a modern home that really needs or is better on AC?
We have some old ceiling and exhaust fans, but I know those can be replaced. Our refrigerator is AC, but extended family with an off-grid home has a DC refrigerator that cycles way less, probably due to multiple design factors but I’m sure the lack of transformer heat is part of it. I’m not as sure about laundry machine or oven/cooktop options but I believe those are also running on DC in the off-grid home without inverters.
Most of these AC appliances also have transformers in them anyway for the control boards. It seems kind of insane to me that we are still doing things this way.
The datacenter I built in 2007 was DC.
Many datacenters I'd been to at that point were already DC.
Didn't think this was that new of a trend in 2026, but also acknowledge I did not visit more than a handful of datacenters since 2007.
It just seemed like a undenyably logical thing to do.
its really wild at all the AC to DC changes. for those non electric engineers / hardware hackers (like myself) one of the biggest "examples" I've seen of this has been ceiling fans.
Installing a ceiling fan used to be treacherous and so heavy. Also loud and buzzy after installed. Now the fans in these things are so lightweight and easy.
seeing the same in many more areas (lighting, etc)
Waiting for home DC.
It is silly to have AC to DC converters in all of my wall connected electronics ( LED bulbs, home controller, computer equipment etc )
I don't understand why new houses don't just have one high quality AC/DC converter so you can just use LED lighting without every bulb needing its own AC/DC converter. I imagine the light bulb cartel wouldn't really like that.
They were Thunderstruck?
It does make a whole lot is sense. The amount of energy you loose to convert AC to DC can be humongous . And useless if you produce your own power (normally already in DC).
They're still converting from AC to DC at the datacenter, it just isn't being stepped down at the perimeter. There is no transmission of HVDC going on. This isn't really Edison's revenge, more like his consolation price, ha!
I wonder how much of the benefit is simpler redundant power equipment. For AC, you have standby UPSes and line-interactive UPSes and frequency and phase synchronization. And everything needs a bit more hold-up time because, in case of failure, your new power supply might be at a zero crossing.
For 800V DC, a simple UPS could interface with the main supply using just a pair of (large) diodes, and a more complex and more efficient one could use some fancy solid state switches, but there’s no need for anything as complex as a line-interactive AC UPS.
Our houses should be DC. So wasteful to have all these bricks to change to AC to DC.
Anyone notice that 400V and 800V are also used in EV battery architecture? I wonder if there's any sharing of technology?
"How can we turn this technical story into a story about people and their conflicts?"
I’ve always wondered about these new High-Voltage DC (HVDC) transmission lines.
I always thought AC’s primary benefit was its transmission efficiency??
Would love to learn if anyone knows more about this
How is DC better than a three phase delta 800Vrms, at 400Hz?
- Three conductors vs two, but they can be the next gauge up since the current flows on three conductors
- no significant skin effect at 400Hz -> use speaker wire, lol.
- large voltage/current DC brakers are.. gnarly, and expensive. DC does not like to stop flowing
- The 400Hz distribution industry is massive; the entire aerospace industry runs on it. No need for niche or custom parts.
- 3 phase @ 400Hz is x6 = 2.4kHz. Six diodes will rectify it with almost no relevant amount of ripple (Vmin is 87% of Vmax) and very small caps will smooth it.
As an aside, with three (or more) phase you can use multi-tap transformers and get an arbitrary number of poles. 7 phases at 400Hz -> 5.6kHz. Your PSU is now 14 diodes and a ceramic cap.
- you still get to use step up/down transformers, but at 400Hz they're very small.
- merging power sources is a lot easier (but for the phase angle)
- DC-DC converters are great, but you're not going to beat a transformer in efficiency or reliability
This article seems to imply that 800V DC is high-voltage DC, but that seems quite low.
Transitioning? It already happened decades ago. Only smaller scale/generic or less proficient "we bought all Dell and HP" use AC. At large scale it's been a ton of DC for literally decades. And for 70 years in telco and network gear.
Have a solar system at home and from the panels it is DC into the batteries but then the inverter needs to convert it to 220V/50Hz AC for home use.
AC is also waaaay safer for households: since the power drop to to zero 100x (50Hz) per second switches are cheaper and safer, and electrocution is less likely to happen.
The large brick you have on all your tech when you plug it in is the converter. AC works great for some applications, none of them really technical in nature.
It is absolutely stupid to talk about this as edisons revenge. If Tesla had the modern high power transistors needed to get high voltage dc out of the ac produced from a spinning turbine he would be all for high voltage dc too. Tesla understood that high voltage was needed for efficient long range transmission. He also understood that transformers were the inly remotely efficient way to climb up to and down from these high voltages. And transformers only work with ac. So he designed an ac system and even designed some better transformers for it.
If there was anything like a high power transistor back then he would have used that. High power transistors that are robust enough to handle the grid were designed inly recently over 100 years after the tesla/edison ac/dc argument.
That is about like aying the band AC DC had its revenge.....
can we stop vibe generating headlines?