Toyoko Inn Shin-yokohama Ekimae Honkan

Not only does this place have a/c each room is able to control the temperature, so you can set it (within reason) to your own preferred temperature. I only stayed here for one night as a stopover after landing in Haneda, so other than its proximity to the shinkansen at Shin-Yokohama station (which was great) I don't have an opinion about much else at the hotel.

We only stayed there for one night on the way from Hakone to Tokyo. We wanted to split the journey and have a comfortable sleep. Alas, the beds and the pillows were so extremely hard, that we couldn't get normal sleep. I'd say the hotel is very decent for the price, however, having a sleepless and uncomfortable night trumps all of its advantages.