Mitzi posted our old dryer for sale on Facebook (Marketplace?), explaining why we were selling it. We have a neighbor who is something of a know-it-all. (Which is really irritating to those of us who actually do know everything.)

Well, he decided to tell us that our heat pump dryer won't save any energy, and may end up using more energy than our conventional dryer. That they were only suitable in Europe where they don't rely as much on air conditioning and where it's often difficult to install vents because of older construction.

Because he's an insufferable know-it-all, he cites references. In this case, it was a 2015 study about energy conservation interventions in some south Florida homes. I know all this, not because I'm on Facebook, but because Mitzi is and she shared it with me. Doubt about the wisdom of our purchase was unspoken but detectable. She wanted something to reply to him.

So I read the study. I'm not qualified to speak to the validity of the study methods, but it did seem flawed to me. One of the data points that they relied on was that the temperature in the laundry rooms of homes with interior laundries spiked when clothes were being dried, up into the 90s in many cases. This obviously adds additional heat load to the home's HVAC system.

But the product they were using in the study was a Whirlpool ventless hybrid dryer. It had a heat pump for "eco" mode, but it also had a resistive heating element for those users accustomed to shorter drying times. It was also a typical American 7 cubic foot dryer. What wasn't clear to me from the data, was how often the resistive heating element was used. And a resistive heating element is not only going to heat the air going into the dryer, some of that will be radiated into the room, in addition to any radiant heat from the heat pump.

In any event, the "combined efficiency factor" for this 10-year-old product was 42% less than the LG we purchased (3.7lbs/kWh vs. 6.4lbs/kWh). I don't know if that's because of some consideration of the resistive heating element, or advances in heat pump design. In any event, the LG is much more efficient.

I gave Mitzi a blurb pointing this out and he responded something along the lines, "Well, time will tell." I later learned that he'd just gone through a laundry upgrade and considered and rejected a ventless heat pump dryer on the basis of that 2015 study.

He then felt it was necessary to point out that the largest electrical load in the home, after air conditioning, is the hot water heater and had we considered replacing that with a hybrid model? Mitzi was pleased to reply that we did so the day we moved in.

Anyway, all this did compel me to do some additional reading about washers and dryers. Mitzi is less keen on replacing her washer now, but she said she won't veto it if I do so, which means it's on my nickel. I read that these ventless dryers are almost always sold as pairs with a washer, often to be stacked, but also because of the size difference. It does look rather odd, such a small dryer next to our huge washing machine. But also because these heat pump dryers are even more efficient with the higher efficiency front-loading washers, that run at 1400rpm or greater during the extraction cycle.

We have a top-loading LG washer because Mitzi prefers those to front-loaders, and it spins at 950rpm during the extraction cycle. I've always thought that the clothes felt pretty "dry" coming out of the washer. For most of my life I'd been using the cheap, low-efficiency washing machines and clothes were definitely wet when you put them in the dryer. Our LG is rated as a "high efficiency" washer, it measures the load and only adds enough water as necessary to accommodate the size of the load. And I think 950rpm is still much higher than a conventional washer, and so more water is extracted.

But I'm inclined to "do my best," so I told her I'd go ahead and get the matching washer for the dryer when we get back from our summer vacation. It's back-ordered right now anyway, and we have something of a busy travel schedule coming up. When we get back, we'll have time and resources to do it properly. She can decide if she wants to stack them and remove one of the cabinets and maybe install a sink in the laundry room.

Originally posted at Nice Marmot 08:33 Wednesday, 3 April 2024