Re: number of outlets on a circuit

There is a general rule of thumb though. Maybe 10ish receptacles? But again, it's all about use. I tend to prefer to put more receptacles in a room than the minimum just for the convenience of plugging things in. Having more receptacles doesn't increase the load on the circuit. So I may have more receptacles on a circuit than the general rule.

With lighting, it's all about the actual load. You can have a ton of LED lights on a circuit vs incandescent.

You don't mention your location. Based on comments from other sources, I believe the Canadian electrical code does have a limit for the number of receptacles on a circuit. The code adopted by most US locations does not specify a number.

Another thing to consider is that GFCI and AFCI requirements have been changing with each code version, so you need to verify which one applies to your receptacles. If your city uses the latest version of the code (which it may not), a very large number of the circuits need either GFCI or AFCI protection.

Some GFCI requirements are also kind of quirky - for example, you need a GFCI for any receptacle within 6 feet of a sink, unless its the receptacle for the disposal (which is probably within 6 inches of the sink).

Bruce

Eh? There's no exemption for garbage disposals in the NEC nor has their ever been. It used to be that the receptacle under a kitchen sink didn't need to have a GFCI as the "6 feet from a sink" rule didn't apply to kitchens. That was changed in the 2017 code. If your disposal is connected to a receptacle, it better be a GFCI.

In commercial work, IIRC the NEC requires that you allow 180va (1.5 amps at 120v) for each outlet ("outlet" means not just a receptacle, but also a light or other point of consumption). This would be 10 outlets on a 15a circuit and 13 on a 20a circuit.

For residential work, the NEC is mute about this. I think that some states and cities have residential restrictions, so check your local code.

Pros I've talked to have said that, as a rule of thumb, they limit outlets to 9 or 10 on a 15 amp circuit, and 12 or 13 on a 20 amp circuit.

I would argue that with more efficient lighting in new homes, that allowance could probably be increased with no problems on lighting circuits.

Thanks for all the answers guys. Thats great. This is the only way you learn. I just went through huge crash course in steam heating systems this weekend - solved.

I would argue that with all the computer equipment and other electronics in homes today, one SHOULD NOT increase the number of outlets per circuit. Indeed, one should consider DECREASING that number, unless all the receptacles on a circuit are indeed known to be only driving LED lights. And no one is ever going to wire halogen lights in.

When I wired my kitchen in the house I built myself I had a separate circuit for the microwave. The fridge was on its own circuit. I had two separate circuits for the outlets in the kitchen only (in addition to the fridge and microwave) and the lights were all on their own circuit. No wait, the lights shared that circuit with an outlet that was dedicated to the electrical bits in the GAS stove.

I ran separate circuits to the living room and into each of the bedrooms JUST for computer equipment. And another into the living room JUST for the TV, stereo, and gaming consoles. Did not share that circuit with any lights or any of the other receptacles in the room.

If you plug a computer into the same circuit as a microwave (or anything else with a similar power draw) you're going to burn out your computer. My son plugged his UPS into an outlet in his dorm room. Then his roommate turned on the microwave. Turned out they were on the same circuit. Blew the UPS but at least the UPS saved his computer. (He did stop whinging about me being "overly cautious" after that though, LOL! My "overkill" - insisting he ALWAYS have a good UPS between the wall outlet and his computer - saved his brand new $2,000 computer)

In the house we were renting a few years ago, the Master Bedroom shared a bathroom circuit that was also shared with the hall outlets and lights in 2 bedrooms AND the hallway. Every time the printer switched on (it was in the hall), the lights in the hallway and the bedrooms would dim. Lucky for him, I don't ever use a hair dryer, that's all I can say. And no, there wasn't a short in the wall or anything like that. There were just too many lights on the circuit plus everything else already plugged in (his computer and monitor and router and etc) and then laser printer comes on to do its thing, LOL! I remember mapping all those circuits and it was a real Rube Goldberg installation. I've forgotten all the details but it was weird and weirdly underwired, considering it had been built barely 10 years before we moved in. Constructed in 2003.

As for computers - modern computers often have 1000W or more power supply, which would pull about 9A (or more). Granted it won't pull that all the time but it CAN. Then there's your monitor, scanner, router, etc etc etc. Personally I routinely run a dual monitor system. Two BIG monitors. One dedicated 15A circuit is not overkill. In fact a dedicated 20A circuit isn't overkill.

I like a separate circuit for a laser printer as well because wow can those spike when they turn on. Yup, I want a separate circuit for my computer, and another separate circuit for the printer. Microwaves, real printers, computers, stoves, dryers, these guys need their own circuits. And hair dryers in the bathroom? There shouldn't be anything on the bathroom circuits that isn't actually IN the bathroom.

Sure, LEDs are starting to get cheaper, and they only use about 80% of the power that it takes to get the same lumens out of an incandescent bulb. But builders have already been pushing it by building with the assumption that lights were going to be CFLs (now being edged out by the even more efficient less power gobbling LEDs) without considering all the OTHER things we need to plug in.

Dudes. It isn't just lights. If ALL you've got on the circuit is lights, no outlets, that's one thing. But BUILDERS put lights AND "regular" outlets on the same circuits, often across more than one room. The only house I have EVER lived in where that was not the case was the one I built myself, LOL!

As for computers - modern computers often have 1000W or more power supply

I didn't read your whole post, but this jumped out at me. I'm pretty sure that's the OUTPUT wattage of the power supply in a computer which is at 12v I believe. That isn't what the computer is drawing in at 120V. It's a level of magnitude less.

Computers are not big energy hogs.

Eh? If the power supply is delivering 1000W on the output, it is drawing at least 1000W on the input side. It isn't generating power on it's own. In actuallity, it's not 100% efficient and putting out some heat.

The big question is how much LOAD is on the output. It's probably not anywhere near 1000W, despite what the computer claims.

But this shows the fundamental truth here.... FIGURE OUT WHAT THE LOAD IS OR WILL BE and design things apprpriately.

While Zen has some good points, it also he doesn't understand the basic tenets of the electrical code, so one needs to be very careful when reading.

I just realized that my logic is way off in that last post (I needed my morning coffee). But I think my conclusion is correct that computers aren't drawing that much :)

I googled around a bit and it looks like desktop computers use around 60-250W. So maybe the 1000W that you mention is the power supply's rated maximum output? But the computer never uses anywhere close to that.

100W usage is what I was guesstimating in my head when I posted that extremely wrong insinuation that voltage matters. :)

"Every time the printer switched on (it was in the hall), the lights in the hallway and the bedrooms would dim."

Yep, laser printers will do that. The fuser is a fairly big resistive heater.

"If you plug a computer into the same circuit as a microwave (or anything
else with a similar power draw) you're going to burn out your computer."

Some appliances can put noise on the powerline, which can cause odd behavior in digital electronics. But in 34 years of using home computers, I've never seen an outright failure caused by this.

I wonder what really happened to your son's computer. :)

A little anecdote: When I was in college, we had a guy on our dorm floor who blasted his huge stereo way too often. (Nobody liked his music, either.) He'd hung twin lead wire out his window to pick up FM stations. One of my floormates decided one sleepless night that he'd had enough. He grabbed the antenna lead and pulled it in through the restroom window. He then connected an AC plug to it and plugged it in. Things quieted down for a while after that.

No, I'm not the one who did it! It takes a certain kind of mind to think of things like that, and I don't have it, thank goodness.

Anyway, a UPS is nice, but just a surge protector will keep powerline surges out. I also recommend surge suppression on Ethernet connections, especially if the cables are long. Before I started using them, I lost 2 NICs to nearby lightning strikes.

I also lost a modem before I added an extra surge suppressor to the phone line. And a parallel port, but I couldn't find a surge protector for that. Luckily, I haven't yet lost a mainboard to lightning.

"modern computers often have 1000W or more power supply, which would pull about 9A (or more). Granted it won't pull that all the time but it CAN"

I just looked at a few replacement computer power supplies. Most were in the 450-600 Watt range, with a few around 700 Watts.

Maybe there are some in the kilowatt range, but that's peak power capability. It's like home stereo power amplifiers. You might have a 400 Watt amp, but if you actually listened at that level continuously, you'd go deaf. The extra power is there to handle brief (milliseconds or less) peaks. (FWIW, until around the 1960s, 20-30 watts was considered enough for a large auditorium.)

In my experience, a typical desktop computer box draws around 100-150 Watts in routine operation. A gamer's machine might use more, but nothing like 1000W.

A laptop uses 20-35 Watts, more when it's also charging its battery..

"Then there's your monitor, scanner, router, etc etc etc."

The old CRT monitors could be energy hogs, chowing down 100 Watts or more. A typical LCD monitor with CCF or LED backlight uses much less, 30-50 Watts.

My scanner's specs say it uses 17 Watts when scanning, 15 Watts when in standby, and 5 Watts "sleeping."

My router uses 7 Watts (measured).

"I like a separate circuit for a laser printer as well because wow can those spike when they turn on."

As I said above, laser printers DO use a surprising amount of power, especially compared to inkjets. But while you might need a separate circuit for a huge commercial or DP center sized laser printer, for a home model I'd call it overkill. Certainly I've never felt a need for a separate circuit for mine.

"Microwaves, real printers, computers, stoves, dryers, these guys need their own circuits."

Microwaves? If the manufacturer calls for a dedicated circuit in the instructions, yes. But most countertop models can share a circuit. They're designed to.

I don't know what a "real printer" might be, so I can't speak about that.

Stoves, dryers, yes; but the NEC requires it, so you don't have a choice.

"Sure, LEDs are starting to get cheaper, and they only use about 80% of
the power that it takes to get the same lumens out of an incandescent
bulb."

WAY less than 80%. A decent LED light typically uses 10-20% of the energy/power that an equivalent incandescent bulb uses.

"But builders have already been pushing it by building with the
assumption that lights were going to be CFLs (now being edged out by the
even more efficient less power gobbling LEDs)"

I wouldn't say they're "pushing it." They're doing their jobs with the load calculations.

I expect that eventually the NFPA will realize that with LED lighting using 10-20% of the power that equivalent incandescent does, we really don't need AGW 12 or 14 wire for lighting circuits. IMO, they should allow smaller-gauge wiring (maybe AWG 16 protected at 10 amps) on dedicated lighting circuits.

Funny you should mention LEDs and CFs, though. LEDs should be more efficient than CFs. They should get 80-100 lumens per Watt, but you'd be surprised at how many don't.

I have a disk light that IIRC manages only 56 lumens per watt. I bought some Feit R30 lamps for a friend a while back; they were 65 lumens per watt. Some of the cheap dollar store and direct-from-China LED retrofits sold online fall into the 40s.

There are cheap and inefficient CFs too, but most of the ones I still have in my house run 65-80 lumens/Watt (or at least did when they were new). Electronically ballasted T8 and T5 linear fluorescents routinely rival good LEDs at 80-100 lumens per watt.

Dude, I'm a software engineer. I'm not even going to read the rest of your very lengthy comment because you are so dead wrong RIGHT at the beginning that nothing you have to say could POSSIBLY be of any import.

It's not noise on the line. It's the spike when it powers on that is the problem. I know EXACTLY what happened to my son's UPS - it got hit by a power surge when the microwave came on.

If you don't know that much, you don't know enough to bother with.

"If you plug a computer into the same circuit as a microwave (or anything else with a similar power draw) you're going to burn out your computer. "

Not even close. Powering a microwave or refrigerator on a circuit with a refrigerator, TV, or router does no hardware damage. As in none.

Meanwhile, if a major appliance causes lights to dim (clearly a brownout; not a surge), then that building has wiring problems. In most cases, just bad workmanship. In rare cases, that dimming light indicates a serious human safety issue. Informed homeowners would never ignore that warning.

No power cycling appliance (printer, washing machine, refrigerator, central air) should cause lights to increase or decrease intensity. In part, because copper wires are so large.

So what would explain dimming? Maybe someone foolishly connected wires to receptacles using the backstab method. Other reasons can also explain it. But this is clear. If that printer causes lights to dim, then a workmanship defect exists.

What happens when a major appliance causes dimming - a lower AC voltage? Nothing. Ideal power for all electronics is even when lights dim to 50% intensity. What does a power supply do? Make all such massive variations irrelevant.

Junk science is a conclusion made only from observation. What destroyed a UPS? Clearly not a microwave - once one learns some basic electrical concepts. Blaming a microwave was only from observation - a classic example of junk science reasoning.

One who really knows computers also knows a UPS does not protect hardware. A UPS is temporary and 'dirty' power so that unsaved data can be saved. A real engineer would cite the UPS specification number that defines hardware protection. Good luck. No such spec number exists.

You made me go look. My PC (of which I built some time ago) has a 750W supply in it. Does it use this much? Nope. But today it is possible to have multiple large disk drives, high power CPUs, and multiple graphic processor boards. My CPU draws about 100w itself (and yes, it gets hot). All told, it's probably pulling 250w. A big game machine or a media center PC would pull more.

Computer assemblers typically know nothing about electricity. So part picker programs and other 'sources' exaggerate power requirements. For some reason, a 250 watt computer would typically require more than a 500 watt supply. Because actual numbers are unknown.

Same applies to the actual power requirements of a CPU. It would be significantly less than 100 watts. Yes it gets hot but no where near hot enough to toast bread. And not as hot as a 100 watt incandescent bulb. Meanwhile, does a computer consume 250 watts? Probably. Almost no computer needs more than 350 watts total.

Meanwhile, does a microwave create a more than 600 volt impulse on power on or off? Of course not. Otherwise the impulse that might destroy a computer would also be destroying a less robust computer inside a microwave.

When a 120 volt major appliance powers on, it does not create a 300+ volt spike. Large demand for current means voltage may drop - not increase. If household wiring has workmanship problems, then voltage may drop so much as to cause incandescent bulbs to dim. But that microwave would not destroy a UPS. And that UPS does nothing to protect electronics.

Too much knowledge is only from hearsay, wild speculation, and the myth of spikes created by a powering on appliance. Does not and cannot happen.

Actually, it IS possible for large appliances to generate power line spikes. I'm not talking about surges here; those are typically only a couple of percent and are of little significance. I'm talking about short duration spikes, which can easily run into the thousands of volts.

These spikes don't happen when the appliance is switched off normally (either manually or automatically). They happen when a fuse or circuit breaker opens ahead of both that appliance and other household items in parallel with them on the circuit.

When you interrupt power to an inductive load, such as a motor or a big transformer, it will "kick back" an induced voltage as the magnetic field in the inductance abruptly collapses. But if you turn that appliance off with its own power switch, it's disconnected from the power source. So the spike is contained inside the offending appliance itself, and can't bother other appliances on the same circuit.

The fuse or breaker that opened to cause this spike might be in your main panel. It might also be a recloser in the commercial power system. That's why power cuts can be stressful for electronics. In fact, I lost a beloved scanner recently, when a tree fell across the power line up the road from my house. It wasn't until I unplugged it to give it a proper funeral that I realized I hadn't had it plugged into the TVSS that supplied the rest of my computer gear. Dumb. :(

Transients like that are a fact of life, so appliances and electronics are designed to resist them. But (simplifying here) every time they do, they lose a little ability to resist the next one. Over many years, they can get to a point where they just can't stand it any more. As a general rule, the better quality the device is, the longer it can resist, but they all degrade. My 18+ year old scanner had apparently gotten to that point.

Adding a TVSS (transient voltage surge suppressor, or "surge protector") to your computer or other electronic device helps absorb those spikes, and extends the device's ability to protect itself. But note that TVSSes also degrade as they deal with spikes. They should be replaced after several years of use. Most of them have LEDs that supposedly indicate "protection active." Just because those LEDs are still on doesn't mean that they're still providing the same level of protection they did when they were new.

To bring this back around to what we've been talking about, note again what I said above: significant voltage spikes don't get sent into the power line when your refrigerator, water pump, furnace, or whatever turns off (or on) by its own switch. Your microwave is unlikely to damage your computer, or even its UPS.

That said, I still recommend buying a good quality TVSS to plug sensitive electronics into. TVSSes are usually built into UPSes. But don't forget, they degrade over time, and eventually need to be replaced, even if they still seem to be working fine.

" For some reason, a 250 watt computer would typically require more than a 500 watt supply. Because actual numbers are unknown."

Actually, the larger supply is there because the 'assembler' doesn't know what the end user may eventually install as an accessory, like more memory, additional disk drives, and the aforementioned GPUs.

"Same applies to the actual power requirements of a CPU. It would be significantly less than 100 watts. Yes it gets hot..."

AMD's specification for power for the CPU I have is 95 watts. Which is why it has an aluminum 'brick' with a fan as a heat sink. That 'brick' (a 3" cube) is currently running at 110* sitting here with the CPU idling.

200 or 350 watt supply in computer company systems designed by engineers is more than sufficient for upgrades. For example, how many watts do RAMs consumer? Maybe 1. One would never know that the number is that small based upon what lies and myths tell computer assemblers. Why do engineers know better? They don't read hearay and other subjective fears. They read datasheets.

How many watts does hearsay and subjective speculation assume for a disk drive? 10 or 20 watts. How did USB ports power a disk drive? A USB port could not provide more than 2.5 watts. Because those peripherals never consume what hearsay and subjective claims say.

Total power says nothing useful. But that means a computer assembler must remember / learn concepts taught in high school science. That means power only for each rail must be calculated. Since that knowledge (and numbers from datasheets) is forgotten or ignored, we learned long ago to tell computer assemblers that a 2 watt disk drive required 20 watts. And a memory stick requires 10 watts. Then help lines are not clogged teaching basic electrical concepts to computer assemblers.

"Actually, it IS possible for large appliances to generate power line spikes. I'm not talking about surges here; those are typically only a couple of percent and are of little significance. I'm talking about short duration spikes, which can easily run into the thousands of volts."

That is popular when facts come from speculation and are not based in spec numbers. If an appliance generates spikes as claimed, then a first appliance destroyed is the spike generating appliance.

Second, if an appliance is generating such spikes, then you are replacing a dishwasher, dimmer switches, furnace, clock radios, microwave oven, GFCIs, door bell, LED & CFL bulbs, toaster, and smoke detectors daily. How many did you replace today? None? Why? Because those spike do not exist.

Third, if a spike is created by an appliance, then we do not put a protector on its victim. Instead we put it on the spike generator.

And finally, plug-in protectors would degrade to nothing quickly (days or weeks) if an appliance was routinely generating those spikes. Anyone can read charts from MOV datasheets. Most don't. Most simply recite the first fear promoted by some irresponsible third party with an agenda. Did we not learn anything from Saddam's WMDs?

If cutting off power creates that inductive spike, then it is create 120 times every second. 60 Hz power cuts off (goes to zero) twice with each cycle.

A scanner was damaged because only observation only generated a conclusion. You did not even identify an internal part that was damaged. Conclusions from observation are classic called junk science.

Meanwhile they also made that same conclusion about a computer that had worked continuously for months. They turned it off once. And it would no longer restart. Then one, who first learns facts before making a conclusion, did an analysis. A bootstrap resistor had failed maybe months earlier. Its only function is to provide power on startup. Damage only speculated from power cycling was actually a failure weeks earlier due to too many hours of operation.

Again, one learns hard facts long before making a conclusion. The myth of major appliance power cycling is popular when junk science replaces reality.

Meanwhile, had one properly earthed a 'whole house' protector, then even appliance generated surges do not exist. That (and not any plug-in magic boxes) is always recommended when a recommendation comes from others who first learn basic electrical concepts.

Why do so many install grossly oversized power supplies? Lack of basic electrical concepts is routine among computer assemblers. The informed never waste money on magic plug-in boxes (TVSS, protector, arrestor, SPD, VPR, suppresser) recommended by ignoring spec numbers. Computers rarely consume 350 watts. And consume somewhere between 100 and 200 watts most of the time. Household appliances do not create those massive spikes.

Potentially destructive spikes occur maybe once every seven years. And are only averted by a properly earthed 'whole house' solution. How often do you suffer such spikes? A number that can vary even in the same town. So an informed homeowner learns neighborhood history from a past 10 or 20 years.

This paper explains how inductive loads can induce transients in other loads connected in parallel when a fuse or breaker opens. Littelfuse Transients Application Note

Computer power supplies are oversized for the same reason that digital cameras with crummy, low-resolution glass lenses have 12 megapixel sensors. It's advertising to the "bigger is always better" mindset. As long as it sells more stuff, the manufacturers will keep doing it.

Now read where those transients are only noise - if from appliances. And then read about transients that are potentially destructive. Each potentially destructive transient comes from outside - ie utility switching, wind, lightning, tree rodents, stray cars, and linemen errors. Once that transient is inside, then it hunts for earth ground destructively via appliances.

If the transient is tiny stuff described above, then electronics routinely convert that transient into rock stable, low DC voltages to safely power semiconductors. (MOVs are not used.) Concern are transients that can even blow through exiting appliance protection. Those must dissipate harmlessly outside the building.

An informed consumer does not spend massively on those near zero joule magic boxes. Informed consumers spend about $1 per appliance from protection from those potentially destructive transients (including direct lightning strikes). Even those magic box TVSS proetctors must be protected. Otherwise catastrophic events have happened such as this: http://imgur.com/hwCWHMW or this: https://i.redd.it/zbvug3xsscw01.jpg or this: http://zerosurge.com/truth-about-movs/

As someone who has worked in a Data Center (several in fact) and has worked with computers all my life I think I would like to correct some misconceptions on UPS's.

First, UPS stands for Uninterruptible Power Supply. They are a source of clean, consistent power. And, they will save your hardware. And your ass.

For most Data Centers, they have a farm of UPS devices that are rotated in and out of service due to repair, demand, etc. But, there is always more than enough supply to greatly exceed any demand required.

UPS are primarily batteries. The batteries feed the data center with clean, consistent, pure sign wave power. No spikes, No voltage drops. Just clean power. The batteries are constantly being recharged by what is essentially filtered power.

The electrical power that comes in from the street to the data centers, or your homes for that matter, is anything BUT clean. For grins and giggles, take a look at it through an oscilloscope and while you may see a general sign wave in there somewhere, you see all sorts of transients, spikes, etc...

All of my electronic equipment, which now includes LED light bulbs, is plugged into a surge protector. All of my TV's, including surround sound, game systems, etc, are plugged into a UPS, through a surge protector.

And, I buy good surge protectors, not power strips. There is a difference.

UPS are not just so you can save your data. They were at one time but most modern computers and software save your data for you automagically. As long as you are smart enough to turn that feature on.

I should point out that your data center UPS is a far cry from the crap sold for home use. I've had cheap-ass trip-lites crash and burn and take out equipment they were supposed to protect.

AC power created from DC batteries always is 'dirty'. So one always posts a number to define 'clean' - such as %THD.

This 120 volt UPS is perfectly ideal power for electronics. When power comes from a battery, then it outputs 200 volts square waves with a spike of up to 270 volts.

Does that damage hardware? If it did, then he has posted the 'at risk' part and numbers from its datasheet. He cannot. No part is harmed. No datasheet numbers define an 'at risk' part. The threat only comes from emotions.

UPS is promoted to 'clean' electricity when one only installs stuff - does not learn what exists or what is relevant. For example, how is that incoming power converted to DC voltages?

First, AC power (clean or dirty) is filtered. Then converted to DC. Then filtered again. Then converted to well over 300 volt radio frequency spikes. Does not matter how clean that power is. It is then made that 'dirty' - high voltage radio frequency spikes.

Then superior filters, galvanic isolation, and regulators convert that well over 300 volt spikes into rock stable, low DC voltages that do not vary by even 0.2 volts. Best cleaning already exists inside electronics.

Why would anyone massively clean AC power that is intentionally made so much more 'dirty'? Too many never learn how this stuff works. To many are only educated by their emotions. "It is dirty so it must be bad". Too many forget a subjective conclusion is probably a scam.

How to make surge damage easier? Plug appliances into a surge protector. Anyone can learn why by first learning what a surge is - and its numbers. Most educated by hearsay, wild speculation, advertising, subjective reasoning (no numbers) and their emotions will never learn why. Will only recited what propaganda has ordered them to believe.

Anyone who actually knows about data centers (and other 'must not fail' facilities) knows what always exists to protect from surges. Apparently he has confused a UPS (temporary and 'dirty' power ) with surge protection (where hundreds of thousands of joules harmlessly dissipate).

If the UPS is so clean, then we read %THD numbers. Not provided. He has only recited profitable urban myths that advertising ordered him to believe.

UPS is not a surge protector. Any effective plug-in protector must explain where hundreds of thousands of joule harmlessly dissipate. Quality protectors are never found in plug-in boxes.

A protector is only as effective as its earth ground. With reams of numbers previously posted that explain why.

A properly earthed 'whole house' solution does 99.5% to 99.9% protection. Plug-in magic boxes do maybe another 0.2%. And cost tens or 100 times more money - to pay for advertising that so easily manipulates the naive - who always ignore numbers.

Define a quality protector. Honesty always provides numbers. What numbers define a quality protector? No numbers means the conclusion is subjective - a potential scam.

Most home-office UPS devices also provide some level of transient protection.

Most also have some amount of filtering to get rid of RF noise that might ride in on the mains.

Not surprisingly, the better and more expensive the UPS, the better its transient protection and filtering are.

The other thing you get with a higher UPS price is a bigger built-in battery, for longer run time.

What you don't generally get in a home-office UPS at any price is clean power. The typical home-office UPS produces low-quality square wave power. (Utility power is a smooth sine wave.) A HO UPS's power quality is even worse than that of your average cheap Ebay no-name Chinese-reference-design "modified sine wave" inverter, which is already pretty dismal.

Here is a short article which explains the differences among different inverter waveforms..

Your computer's power supply doesn't really much care if the input power's waveform is ugly. It can deal. Other components in your system may not be so sanguine, however.

I don't know how many data centers do this, but in the early 2000s I knew of one that used high quality, high reliability true sine wave inverters driven by large float-charged battery banks. A setup like this will produce very clean, mains-like power, It won't be cheap, though.