@calves 

Hey and welcome

It could well be the mix of the older and newer adaptors.  The older adaptor is AC1 standard so uses a single data connection, the AC2 uses dual data connections

However I have seen that the newer adaptor un-performs when mixed with the older adaptors as its required to change its connection to suit that device, the old "as fast as your slowest device" idea.  You may well find that removing the 600mbps adaptor would speed up the AC2 models.

Also static on the wire could cause this. Homeplugs do cause a level or static after a while on the mains connection and from experience disconnecting them overnight once in a while helps massively.  This allows the static to clear and the route tends to work better, i done this every 3-4 months with my plugs.

However.. I have to be honest and say if you are just upgraded to 1000/200 WAN speeds, this may be the wrong choice for you.    In short homeplugs are SLOW, even compared to WiFi.   Their main advantage is stability, something WiFi doesnt do well at all.  

As the plugs are rated 1200mbps, thats the theoretical maximum and real speeds will be a LOT less, I would expect around 33% of what the connection speed reads at.    The connection you have reading 427, in real speeds that is likely around 220/250mbps.  With such fast internet that is a MASSIVE bottleneck for you

If you are after faster speeds you may find that the Deco range (something like S4) would be a better option for you, seen these getting 400mbps solid are generally very good.   

In short for the internet speeds you are throwing, power lines are not the best choice... fast WiFi would be easier and arguably faster for you.

Hi @Philbert 

Thanks for such a detailed reply.

I tried removing the old adapter but it didn't improve.

To be fair, when I first paired the new adapters, I plugged everything in two rooms with one of them being where the router is and the speed between adapters was pretty good at that moment. 

Obviously I wasn't expecting to have 1 Gbps through powerline but I was hoping to have at least 200-300 Mbps. I guess the problem here is range. Because my normal setup has one adapter in the living room, connected to the router and the other one in my bedroom which is in another floor. But looks like the old adapter has better range or doesn't get as much interference? I think that's kinda weird, but I'll try your suggestion to unplug overnight since I've been running powerline adapters 24/7 for like 6 years. Should I unplug both adapters or just one?

Regarding mesh systems, how reliable would be something like Deco S4? Those systems are signifcantly more expensive so they would need to perform very well.

At the moment I have a WiFi 6 router downstairs and another ONT on the first floor which also supports WiFi 6 (Huawei OptiXstar K562e) but even though I can get 900 Mbps on my iPhone downstars near the router, I can't even get 200 Mbps upstairs near the ONT because the WiFi signal that reaches the first floor and is being extended is already weak, compared to the one downstairs. Wouldn't I have the same problem using Deco? I know those systems are good to eliminate dead zones but I don't have a coverage problem, my problem is speed and I cannot use Ethernet cables through floors/rooms so that's why I was looking at powerlines.

  @calves 

Hey

It does sound like you are in the same boat i was a couple years ago.   Like yourself I had homeplugs (1200 also) and got the same issues that you are seeing, while homeplugs are great they dont scale well and performance is.. well meh sometimes, however they are reliable

You do have a quite a few plugs now which isnt ideal if honest, usually performance does suffer after 4+ plugs due to the volume of data on the cables.   Also the mix of AC1 and AC2 isnt ideal either, homeplugs will only work at your slowest speeds so at moment thats 600mbps regardless of what plugs you use.  Ideally you should be moving everything to AC2 plugs (1000-2000), running any AC1 plugs at all will slow you down.   Sadly however that is $$ to do.. i know first hand

If I was in your scenario and its at all possible, disconnect all the plugs tonight.. leave overnight to let the circuit discharge any static clear then replug only the AC2 (1200) tomorrow and run tests to see if the speed improved, then add the older plugs back in.   Least that way you have a baseline on clear wires with new plugs...

In terms of Deco, they are quite reasonable really.   The S4 model is 100 euro / 120 USD for a 3x pack.  If you place these striaght above eachother on the floors it might be a good option for you. 

Check something like WiFi Analyser on Android and see what signal you get straight above your current router, if its -65db or lower then WiFi could be an option for you.   Never use Apple devices for this, they lie something bad in terms of speed and signal, android or windows all the way for testing. 

Ultimately with 1gbps coming in you really should be considering spending some money on hardware for this.  As said I had the exact same setup as you, homeplugs all the way and got 1gb internet which i could not use.   In the end I had no choice but to run cables externally up trunking to the roofspace then stick in APs. 

In most cases you will find WiFi to be faster than the homeplugs are, however its far from a simple answer.  

Check out this site, it might help you with some tips.  Just take the 3 underscores out of the URL.. stupid external link blocking..

ww_w._makeuseof._com/tag/6-tips-improve-speed-powerline-network/

  @Philbert 

Keep in mind that I only mixed all adapters in the beginning, after that, I removed all my oid adapters, even before creating this post so there should be no problems related to incompatibility since I'm only using 2 adapters of the same kit.

I unplugged both adapters overnight and I think it helped a little bit. Now the speed between adapters is 300 Mbps and in SpeedTest I get 95-115 Mbps which is a little bit better than before.

Regarding mesh systems, I did try one of those apps a couple days ago and I noticed that upstairs I get around -80 dB. That's why I get "slow" speeds on my WiFi extender, because the signal that gets upstairs is already weak. I have other extenders but there are no suitable places to install them between the router and the extender so I don't think there will be a better option here. With mesh, I would face the same problems. And since Ethernet cables are not an option because I don't want to drill or see cables or pvc concealers around the house, I guess I'll be stuck with these speeds.

  @calves 

Hey

Yeah this is not totally unexpected, I had mentioned in the post earlier I expected to see this result

As the plugs are rated 1200mbps, thats the theoretical maximum and real speeds will be a LOT less, I would expect around 33% of what the connection speed reads at.    The connection you have reading 427, in real speeds that is likely around 220/250mbps.  With such fast internet that is a MASSIVE bottleneck for you....

Homeplug work in theory the same way as WiFi does, it will give you a theoretical maximum connection speed but as you are going through a contended medium (literally power going down the same lines) this will massively affect the performance.  In general from experience I find homeplugs to be about 33% of what they claim on average.  Some newer homes with better wiring and lower power LEDs etc a tad faster, older cabling a tad slower..   but 33/40% is the ball park range

The main advantage that home plugs have is stability, you will get 220 or whatever it is now and that will be consistent...   WiFi connection would be faster for you, perhaps even the full 500, but it will be erratic and at times drop massively.   Basically its speed vs stability here

The issue you are going to have is the same that I did, your internet as it passes 500+ will greatly outstrip the capability of the homeplugs, you simply wont get near those speeds and thats you bottleneck.   WiFi will get you closer to the full speeds, possibly even a tad more but getting good coverage is expensive!      Something like the Deco range is good, but littering the place in nodes can quickly become expensive and the more nodes / hops you have the slower it gets.

To be honest, if you want the full 500+ you will need to run cables.   I ended up running up black trunking on the outside wall, coming in at each floor and placing an AP there.   3x WiFi5 APs all connected by a cable backhaul, solid 500mbps all around the house.  I have 1gb coming in so upgrading to WiFi6 would get me closer to the 1gb speeds, but I dont have a need for the full 1gb over WiFi at present.  

With cable you have a un-contended connection and it will deliver ~960mbps out of 1gb all day long.    Its maybe not the answer you want, but it may be your only choice if you really want the fast speeds all around.

Basically we have 3 values:

• A - Theoretical maximum speed: 1200 Mbps
• B - Speed between powerlines (on TP-Link software): 425 Mbps
• C - Speed on end device (SpeedTest): 100 Mbps

I understand there will always be a huge difference between A and C. But I don't understand the difference between B-C. If the upstairs's powerline is actually receiving 425 Mbps from the one downstairs, why isn't this speed reaching my end device? There should be no power interference there, it should be only dependent on the Ethernet ports (of the powerline and the end device) and cable used for the connection between the two. In my mind, it would be logical that the second powerline and the end device received the same speed.

  @Philbert I just want to thank you for such a detailed explanation! I'll stay with this, I don't really need a better internet upstairs, where I actually need good speeds (Apple TV 4K) I have a Ethernet connection directly to the router which results in 920 Mbps in Speedtest. If I could have better speed everywhere, it would be better, but can't justify the investment in a mesh system, for example, at the time being. Thanks again.