Luckily, I got this one running while the kids were still in cotton diapers. It has been clunking along since 1991, saving a few cents worth of electricity per load in the dryer (maybe $200 or $300 saved over 15 years for a family of 4). The cross-flow core has every other slot going side to side, and the balance going up and down. The dryer outgoing air preheats the incoming air, and thus the heating element does not work as hard to bring the incoming air up to temp. The large surface area brings the two airstreams into intimate contact so that, at best, they equilibrate and you get 50% efficiency. The minor problems are condensation in the outgoing stream (gathered in the small sump) and the once a year cleaning to get the lint out of the core.