We live in a 260sf tiny house. Currently we are running a 5k btu and an 8k btu and they are not cooling well enough. Both A/C's are about 3 years old. This is only 1 room + a bathroom so only a single wall dividing. I clean the filters every week with soap to make sure nothing is blocking. That's about how often the filter light comes on. Is this really not enough strength? Or do I just need to replace the units with a new 10k? From everything I've looked at the 8k alone should cool for this sq ft

Yes, very small. When I say tiny home, I mean literally the definition of tiny home (1 room plus a bathroom). I know there is a humidity issue as we are just outside Houston. I've noticed the smaller one, which is a 5050 btu, even though it is blowing cold it isn't putting out much force. The larger one never cycles off even during the mornings. The Windows are double paned. Door is sealed. In the morning it is cold as it should be inside, but by noon it's pushing 80°. By 5pm, it can be close to 90° and God forbid I'm cooking anything. In the winter it stays perfectly warm with an oil heater even during freezing temps. I'm not trying to make it walk in cooler temperature. I'm wanting it to be a decent 73°-75°. I'll see about the temp output on the larger one. Seems pointless on the smaller if it doesn't seem to put out much air flow

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    Is your house poorly insulated? Does it have bad doors/ windows allowing airflow? Are the windows old single pane type? Any number of these factors can mean your house is losing cold (in reality, gaining heat) too fast. Also do the current units run continuously? Jun 6, 2018 at 18:09

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260 Sq Ft? Are you sure, lol. Many variables are missing here. I have cooled 500 sq ft with an 8k window shaker in northern calif. So maybe you can tell where you live. Phoenix? lol. So let's check the units. If you can measure the air coming out of the unit with a thermometer that would be the first clue. It should be in the low 40s or high 30s. Three yrs old is not very ole. Second is insulation and air gaps. Get those two out of the equation and you should be cool as a cucumber.


One thing you need to consider is the fact that in a "tiny house" the ratio of the exterior surface is extremely high compared to the interior volume. So your 260sq.ft of floor space has a massive heat gain compared to a 260 sq.ft bedroom in a regular house. Your tiny house is completely enveloped in heat. It's probably not very well insulated either and I would imagine a large percentage is windows. Plus two people at rest add 1000btus/hour never mind if you are doing anything "active". With all that in mind I would think that 13,000btus total would do the job but I wouldn't be surprised if you required 24,000btus (2tons) based on a back of the envelop heat gain calculation. Square footage doesn't count for much in heat loss/heat gain it's all about exterior exposure.

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