Does more RAM usage cause more battery usage?

Solution 1:

Memory is a negligible factor, because it uses very little power (we're talking less than 3 watts per stick in a laptop).

And in fact, if you have a HDD, more memory usage would theoretically increase battery performance, because there is less HDD activity when memory is used as cache, instead.

The most power hungry components are ones that generate heat (CPU and GPU as they process information) and those that generate physical motion (the fans and any hard drives). Memory tends to generate relatively little heat (and obviously no physical motion).

The first steps I would take to reduce battery consumption would be to replace the HDD with an SSD, get a new battery and maybe replace the fans with those of better quality (harder to do on a laptop). Also abstain from any GPU or CPU intensive tasks. Any efforts beyond that are adding immeasurably small amounts of battery life.

Solution 2:

No. Keeping memory "clean" is generally not necessary (though that doesn't mean one should waste it).

In its strictest sense, keeping memory "clean" may even be a very ill-advised idea. Although there exist so-called "memory optimizer" software where you pay for a program that keeps your memory "free" by purging filesystem caches, unloading DLLs, and trimming working sets, this kind of thing is snake oil.

RAM is meant to be used, if you keep RAM free, then you could as well have spent less money and bought less of it. In every modern operating system, memory pages that come from mappings are transparently migrated to and from the filesystem cache, which is not only much faster but also avoids disk activity. A disk typically consumes about twice as much power when active as compared to being idle. Your RAM consumes the same power either way (in theory, unused memory banks or unused memory modules could be powered down, but in practice this does not happen -- it would be most troublesome if one tried, insofar as physical memory is allocated and released in a pseudorandom way, so finding a complete module that's unused would be a daunting endeavor).
Bringing a program that is already running to the front is obviously faster and more power efficient than loading its image from disk, loading shared libraries, fixing imports, relocating, and starting up. Likewise, pulling a document out of the cache is faster and more power efficient than loading it from disk.

As long as you don't plug in additional memory (which you aren't going to do, since you mentioned you already have "enough"), the power consumption will remain the same.

That said, running lots of programs that serve no particular purpose (not programs that you actually use, or vital system components) is useless, and needlessly takes away RAM that the computer could otherwise use in a meaningful way (for programs or buffers). There is still a difference between keeping RAM used and wasting RAM.

For example, running 10 instances of Google updater, Logitech updater, Adobe updater, Office Speed Loader, Adobe Speed Launcher and so on, all of which do nothing truly useful, will take away memory that the OS could otherwise utilize as filesystem cache. While these programs may get paged out in presence of application need, this doesn't happen in favor of cache, and in any case it means needless writes to the swap file, even more so as they'll still have the occasional context switch despite "zero CPU", which would mean a page fault every time.
Thus, feel free to throw away stuff which isn't vital for the system's operation and which doesn't provide anything useful that you want. But don't blindly toss stuff just for ideology.

Solution 3:

I'd agree with Moses' answer; more memory means less disk activity which means less power consumption.

I'd like to elaborate on the hardware however. There are many benchmarks like this one that show the small amounts of power involved. In that example, four 1.35V DDR3 SO-DIMM modules use 4 watts more under load than two modules (so about 2 watts per module, laptops typically have one or two). In any case, using memory alone is preferable to the power consumption of memory and hard drive combined.

Solution 4:

From my understanding of your question, it doesn't matter if you're using 25% of 100% of your RAM; they power needed to keep the data in it is going to be the same.

RAM is considered as a volatile memory, since it needs to be refreshed very frequently (many times per second, in-between read/write cycles). This is why you lose everything that wasn't saved on disk when the power goes out.

This process of refreshing the RAM is done no matter if that part part of your RAM is in use or not.

So, an idle computer will not consume more power if it's RAM is used more; but as it is said in other answers, higher RAM usage likely mean more CPU usage to manage it; and "memory cleaners" are likely to consume more energy processing than leaving the Operating System do its job

Solution 5:

This is answered indirectly in the related question Does installing larger RAM means consuming more energy? and there are many details in the answers there. It's not technically a duplicate question, but they cover that same ground in the answers.

In practice, even at load, the increased consumption is negligible. If the RAM is being used to cache what would otherwise trigger disk or wifi access, the net power savings is enormous as it is deferring power from much more power hungry components.