Woa, Tippi, you have a serious and expensive moisture problem. It has to be leaks or infiltration of moist air. Is it very humid where you live? Do you have dry indoor air in the winter? My experience with mini splits indicates that potential and existing customers are very confused by the manufacturers' language ca. dehumidification. Yes, there is a dehumidify setting, but there is only one coil in the indoor unit. They can only be biased to water removal over cooling by running the fan at the lowest speed and keeping the coil at the lowest practical temperature. This is a very nice feature and is very effective in humidity control when only a little cooling is needed or a little can be tolerated. It is not as effective as a dedicated dehumidifier when one of those is desirable. The commercial units might have two coils in the indoor unit. I have not seen that, but I am not an HVAC pro. They'd also need two sets of lines, one for each coil. What I know they can do is cool and heat adjacent units in the same room, or in adjacent rooms at the same time with the same outdoor unit. This would be an effective dehumidification device in lieu of a dedicated dehumidifier. BTW, this link was posted in a current thread. I thought you might find it of use: Here is a link that might be useful: Roof in FLW-like house

I would not use a minipump if possible. I installed 3 units while the masterbed rm gravity drained to the exterior.the other 2 bedrooms high wall units pumped up to the attic then drained into a plumbing drain stack. The intermittant noise was an issue for the bedrooms. I went back and wraped duct insulation around the pump to help quite it down. It was not extremly noisey but noticable. I probally could have placed those 2 rms on the exterior and drain directly out . but may not look to good on a 100 yr old house front facing.

Ionized, I am always amazed at the workings of Utilities. As I said, there is a significant rebate presence around the mini-splits to reclaim the heating market lost to gas and oil years ago. Remember the 50's & 60's when the mantra was the "Gold Medallion" home? Total electric! the embrace of that concept, low first cost, led to a huge market in gas conversions. That is the primary market I attacked with the Rinnai Energysavers in New England and we sold a couple hundred thousand of them. I've heated my home with them since '91. In conjunction with the mshp's it is just a great combination. Gas is still the right alternative for heat, but as the compressor bearing technology continues to improve and they get better at hot water it is going to be really interesting going forward. So, today, gas for heat and hot water is the right choice, for me at least. Once cooling gets into the equation the heat side is impacted and we'll have to see where it goes. It's a big market and nothing is going to happen all at once. On the duct work leakage question of interior/exterior things definitely get murky. The thing is, every system has a personality. The exterior mounted stuff is the worst. The interior systems have substantial problems too. It is fairly common where due to leakage you create different pressure zones (+/-) in a home that can actually increase infiltration into the space. Snidely, it is difficult to say it is this cost. The output of the units will vary somewhat with temperature. Actually, the Feds don't even know how to accurately determine seer ratings. When I speak with the Japanese Engineers they say the 25's are closer to 35 seer, but we live where we live, so.... 25 it is. I can tell you that in my home here in the dry dry foothills of CA, I heat with my Rinnai EX22 and a dual mshp upstairs. I have a 25 seer 12 and a 23 (?) seer 15 downstairs. I also run a Rinnai tankless for dhw. My 250 gal LP tank lasted 14 months. The house is 2200sq ft. My highest bill to run the whole place peak of winter and summer (well, lights, heat/cool, the works) has been $85 and we do not suffer comfort wise under any circumstances. In the spring/fall shoulder seasons the bill falls to $35-40. If you are looking for heat, I'd absolutely go with the Rinnai's over the mshp's. From a comfort point, gas is hard to beat. From a technology point with the modulating burner, blower, etc the Rinnai's are the best heating appliance I've seen in 50+ years in the business. You have a decision to make on your 40 yr old leaky ducting. If you can find someone to do the job, do not pay for it until the system meets the CA requirement of a max of 6% leakage. I spoke with a contractor who, in Clearlake repaired a single story raised ranch with 12 outlets. two men 1.5 days, $2,400. I spoke with another contractor who repaired big home up in Carson City, $11,500. Yikes! When we moved west 4 years ago my duct system was beyond salvation and would have been impossible, due to access issues, to repair. I pulled it all our and took it and the five year old furnace/condensing unit to the dump. with my current combination of the Rinnai's and mishap, I am all zoned, net to the space and comfortable. Oh, and I gained two closets by removing the ductwork and also gained the storage under the staircase. Doing what I did is a REAL step, but you need to evaluate the whole package first, break it down and see what is best for your home. Fun isn't it?

"Why someone would buy Mitsubishi/Carrier when there is much cheaper option." Because Mitsubishi is an established brand with a good reputation - the others are...... well....... as a rule, an unknown. Note that you can buy a Mitsubishi Mr Cool DIY system for around $1500, but finding a reputable installer may be a challenge (because they can no longer bury the labor charge and/or can't mark up the equipment). The smallest Mr Cool, I believe is 12,000BTU which is too big for your needs. Mitsubishi make smaller units but not in the DIY series, so you end up getting screwed by the contractor again!