We cannot be sure.
KDE Plasma Desktop has no official system requirements that is known to end-users to this answered date. The relevant documentation was either lost during the development, or missing from the beginning.
KDE neon is a relatively new project announced in early 2016, and has noted the minimum requirements for KDE neon User Edition 5.6.
Installing KDE neon requires:
- 64-bit PC (Intel or AMD)
- 2GB memory
- 10GB disk space
Despite featuring the KDE Plasma Desktop, the FAQ page has explained that KDE neon is a rapidly updated software repository, not "the KDE distro" and limited to 64-bit builds only. Hence that is not directly applicable to KDE Plasma Desktop itself.
The only other system requirements (2013) found was relevant to KDE Plasma Active, which is the KDE Plasma 4 for devices with touchscreens. Side note: Plasma Active has been superseded by Plasma Mobile, according to the community wiki.
Basic - Operating System: Linux
Basic - Version: Linux 2.6
Motherboard - Base Memory: 1024MB
Processor: Enable PAE/NX
Video - Video Memory: 128 MB
Video - Enable 3D Acceleration
SATA Controller - Hard Disk - Virtual Size: 8.00 GB
Besides these two sources, KDE does not seem to have prepared any relevant documentation for KDE Plasma Desktop that are accessible to the end-users.
The Fedora Project distributes alternative desktops called "Fedora Spins", which includes the KDE Plasma Desktop variant. Fedora Magazine has published an article about KDE Plasma 5 when the Fedora Spins was under heavy development (2016).
There is a notable mention of performance with KDE Plasma 5:
For those worried about performance and computer resources, Plasma 5 is a good option. It isn’t as heavyweight as previous versions of KDE Plasma, and you can also reduce the number of effects running in your desktop as well if you need to (I was able to run it well with 1GB of RAM in an Atom notebook).
That "Plasma 5" refers to the one included in Fedora 23, which was hinted by the last included link to previous article about Fedora 23 KDE within the article.
Fedora 23 KDE Plasma Desktop features Plasma 5.4.0, KDE Frameworks 5.15, and KDE Applications 15.08.
Within the article about KDE Plasma 5, browsing the comments underneath leads to this meaningful comment left by the author:
Sylvia Sánchez: With Opera or Firefox (both installed), Gimp, LibreOffice and some other nice stuff. Maybe you’d like to read “How do you Fedora, Sylvia Sánchez?”, there’s explained some of the things I do with a 1GB Atom netbook. I don’t know what people do to need that much RAM [...] But don’t say is a joke. My netbook isn’t a joke at all, it’s pretty useful and serious.
Based on the given clue of “How do you Fedora, Sylvia Sánchez?”, looking around the web site leads to the relevant article about the author. Within the article, more information about the hardware was found.
Her computer is a Magalhães 2 netbook, which is Intel’s version of the One Laptop per Child (OLPC) program. Everything is Intel inside and it works very well with Linux in general, and Fedora in particular. It is equipped with a 150GB hard drive, 1GB of RAM, and a 10.1″ screen. The processor is an Intel N450 running at 1.66GHz and is equipped with the GMA3150 card for graphics.
Using "N450" as the keyword to search on the Intel website leads to the product specifications for the Intel Atom® Processor N450 (512K Cache, 1.66 GHz).
Code Name: Products formerly Pineview
Launch Date: Q1'10
Number of Cores: 1
Number of Threads: 2
Max Memory Size (dependent on memory type): 2 GB
Memory Types: DDR2 667
Max number of Memory Channels: 1
Instruction Set 64-bit
Instruction Set Extensions: Intel® SSE2, Intel® SSE3, Intel® SSSE3
Using "GMA3150" as the keyword to search on the web leads to this hardware review on Notebookcheck and this guide on Intel via Intel GMA on Wikipedia. The latter has some information related to Linux.
Found in Intel Atom D4xx, D5xx, N4xx and N5xx (codenamed Pineview) processors. Like GMA 3100 and GMA 3000, this is a very close relative of the GMA900/950, completely different from the GMA X3000 series. Supports up to 384 MB video memory(windows xp driver), DirectX 9.0c, Shader Model 2.0, OpenGL 1.4 with Microsoft Windows and OpenGL 2.1 with Linux.
In related matter, the author whom had left the meaningful comment on Fedora Magazine, was found to be a Fedora Ambassador since 2015 and have been interviewed on Linux Rig.
Q3: What distribution do you run on your main desktop/laptop?
A3: I have a laptop running Fedora 27 and a netbook with Debian Testing.
Q4: What desktop environment do you use and why do you use it?
A4: I use KDE Plasma 5 on Fedora and Xfce with Plank dock on Debian Testing.
Q6: What kind of hardware do you run this setup on?
A6: My laptop is a Dell Latitude E6500, 4GB RAM, dual core, Nvidia, 500GB HDD. My netbook is an Acer Aspire One, Atom N450 single core, 1GB RAM, 250GB HDD.
Interview conducted November 29, 2017
Apparently, the author now runs Debian Xfce and does not run Fedora KDE Plasma Desktop on the netbook. Perhaps a newer release of Fedora is no longer lenient to run on the netbook, since the author choose to run Debian Xfce instead of Fedora Xfce. That however does not tell anything about KDE Plasma Desktop itself.
By connecting the pieces of alternative source, we can summarize that KDE Plasma Desktop has the recommended minimum requirements as follows:
- A single-core processor (launched in 2010)
- 1 GB of RAM (DDR2 667)
- Integrated graphics (GMA 3150)
The requirements were originally found to have been tested with KDE Plasma 5.4; however, KDE Plasma has become more resource efficient in recent years. KDE has made some announcements that supports the claim, with KDE Plasma 5.12: Speed. Stability. Simplicity. and KDE Plasma 5.13: Fast, Lightweight and Full Featured.
Disclaimer: The original author of this answer have tested KDE Plasma 5.12 in Kubuntu 18.04 running on 1 GB RAM with Intel Celeron M 1.6 GHz (2009) that supports only 32-bit and has slightly higher rating than Intel Atom N450 1.66 GHz (2010). Tested from live session, seems usable by default. User experience may be improved by changing some settings: Turn off the desktop effects and disable unused services.
We can now conclude that the recommended minimum requirements for KDE Plasma Desktop, through the alternative source, are indeed notable and deemed usable for daily use. We cannot be sure, but this seems good enough to tell.