I'm new here and don't see a topic on this, so I hope it's not redundant or otherwise obnoxious to create one.

I'm looking into appliance designs for energy & resource efficiency at relatively low cost. The conventional answer in clothes washers is the horizontal axis drum, but there are a few other designs that intrigue me.

I've seen ads for a type of compact washer that use an agitator that consists of a flat or slightly concave circular disc with ridges, which seems to be referred to as a "pulsator." Some of these (or perhaps only larger models primarily outside the US) have smaller circular elements within them that also spin as the main element rotates. I can't tell from the ads, but I would assume that these either a) rotate at a speed of 30 -100 rpm in one direction only, or b) rotate at that speed range but reverse direction periodically.

Question is, how effective are these compared to conventional vertical-axis agitators? Do they cause clothes to tangle because they don't extend to the top of the washtub to above the waterline? (I can recall using a friend's machine many years ago that had a similar impeller mounted on a horizontal axis; I think it was a Hoover. It certainly caused my clothes to get tightly tangled. Perhaps I wasn't using it properly, but I doubt that because I tend to under-load washers rather than overload, to reduce strain on the mechanism.)

In general, what are the most efficient agitator designs in terms of maximum cleaning capability for a given input of water and electricity, without causing undue wear on the clothing?

Impeller/Pulsators are not that great. They are sold here mainly by LG, Samsung and Daewoo. Small Sanyo and Hitachi machines were also very popular in the 80's.

They do tend to tangle clothes horribly. And they are not water efficient, as the cycle course seems to favour multiple deep rinses instead of the usual wash/spin/spray/deeprinse/spin course. They need a full tub of water to agitate, and are very sensitive to overloading. Too much in there and the water goes around but the clothes dont. Load it properly and agitation is brisk and fun to watch.

I must say that those pulsates plates are very rough on clothes. I have a Sanyo and I've use the delicate cycle to wash my 4 plates mats with fringe on extra high water level and two of the mats came out unraveled on the ends which never happened in my DD using the delicate or hand wash cycle.

This machine is only good to pre-treat heavily stained load before the main wash or use as an extractor since the spin speed is a little better than the DD....

But it's fun to see clothes ball up in a knot then reverses to somewhat untangle.....

Very interesting. That would seem to be a "fatal flaw" in the design, so that takes those off my list entirely.

The whole question of agitator design could get pretty complex. What you have is, in essence, a container of material with variable characteristics, that exhibits chaotic fluid dynamics. The flow pattern in a load of underwear and socks is probably radically different than that in a load of blue jeans. Think of mixing mortar vs. mixing stiff concrete with large stones thrown in for good measure. Designing a machine to optimise for one purpose would probably compromise it for the other.

Or are there designs that work equally well under both conditions?

I think the folks at Maytag said it best years ago---"it is not how the clothes move through the water that cleans them, it is how the water moves through the clothes".