Toshiba - 14,000 BTU (12,000 BTU DOE) 115-Volt Inverter Wi-Fi Quiet Portable Air Conditioner w/Heat up to 550 sq. ft. in White (RAC-PT1412HVWRU)

No air conditioner is going to be particularly energy efficient but new ones are as good as they can be. If you have vertically-sliding windows then a window unit is definitely the best way to go. The U-shaped ones are best because you don't need to install brackets on the outside of the building. If you have horizontal-sliding windows then you'll need a portable AC unit, preferably a dual-hose model. The two best dual-hose brands are Midea and Toshiba. They're more expensive than window units but absolutely worth it in the middle of August.

Dual hose units actually work. Single hose units are pretty meh because they're using your cooled inside air to cool the hot side radiator and that gets vented outside, which means that amount of air is being pulled into your cooled space from outside to replace the air being blown out. You may as well open a window and stick a fan in it blowing air in. That's the problem with single hose ac units. As you can imagine they're dramatically less efficient/effective. If your heat is electricity(wall heaters, baseboard, etc...) I'd recommend this unit. https://www.homedepot.com/pep/Toshiba-14-000-BTU-12-000-BTU-DOE-115-Volt-Inverter-Wi-Fi-Quiet-Portable-Air-Conditioner-w-Heat-up-to-550-sq-ft-in-White-RAC-PT1412HVWRU/318747168?source=shoppingads&locale=en-US&pla&mtc=SHOPPING-CM-CML-GGL-D29A-029_017_ACS_FANS-NA-Multi-NA-PLALIA-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl&cm_mmc=SHOPPING-CM-CML-GGL-D29A-029_017_ACS_FANS-NA-Multi-NA-PLALIA-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl-21452948786-166047147484-380908666773&gad_source=1&gad_campaignid=21452948786&gbraid=0AAAAADq61Uf7QTn_kHg7w_-sF0Un-mnGD&gclid=Cj0KCQjwjJrCBhCXARIsAI5x66UPUlwFHHJjzLV3IlOkECPk8qALEHdy2_i4aIh0QsaRIKWVuqnvZk8aAlX_EALw_wcB&gclsrc=aw.ds I have it as well, it works tremendously. It's quiet when it doesn't have to work very hard because of the inverter compressor and it's not like it's insane at full speed. This will give you heat pump heat and save you electricity. It does pump water out a separate tube in heat mode so you have to manage that. In ac mode it's able to send the water out it's air outlet tube. It's a dual hose setup where the 2 hoses are combined in one bigger overall tube. It had no issues with the downstairs of our 1100sq ft townhouse and we had to put it to use one day in our current 2000sq foot single level house with 14ft high ceilings on a 95 degree day when our central ac went out. We kept doors to bedrooms closed and had it in our main living room/kitchen area that opens up to another living room/dining room area, no doors. I had it setup in the morning and it managed to keep the main part of our house from getting above 75 degrees running full power all day. Totally underpowered for that purpose but a house this size is way beyond its capabilities. It did admirably all things considered. It's pretty big. It's pretty heavy. But it works. I see one in Wilsonville on Facebook Marketplace. If you get a new one beware you'll want to run it outside for a couple hours or so before bringing it in. Puts out quite a weird odor at first. It goes away.

https://www.homedepot.com/p/Toshiba-14-000-BTU-12-000-BTU-DOE-115-Volt-Inverter-Wi-Fi-Quiet-Portable-Air-Conditioner-w-Heat-up-to-550-sq-ft-in-White-RAC-PT1412HVWRU/318747168 This will freeze you out. You can buy a hose in hose extension too on amazon I believe.

The Toshiba dual hose one works well, has an inverter as well so less power on lower cooling needs. I think I saw it at Costco lately,maybe under the Madea brand.

Dual Hose is the way to go. Single hose radiates heat from the hose back into the room. I have a Toshiba which worked great all summer and cooled a 800 sqft duplex just fine. It's $600 from Home Depot which is out of your range. HD has some other dual-hose for less but read the reviews.

Toshiba dual hose portable. Any brand with dual hose is better than any single hose portable. When I had a single hose the hose would get very warm and just reheat the room.

It (and it's clones) are the best portable AC's you can buy, thanks to the efficiency of the dual hose. I have the Toshiba rebrand of it and love it

We use Toshiba 14,000 BTU units, with insulated HVAC piping for the exhaust, connected and then taped with thermal tape to prevent leaks. The HVAC piping goes into the ceiling tile, and exhaust out the side of the building. We have hot spares in case one dies. Bonus points, put in some sound deadening material in the server room if the are people in adjacent offices :) A lot of the times it's the exhaust heat that kills the components., the OEM exhaust piping is garbage - usually very hot to the touch. The insulated piping is a world of difference. Also important to drain the condensation and clean the filters monthly.

Me and my wife got a Toshiba one that worked amazing when we were down in Oceanside. And even better once we moved to a drier climate. We got it from home depot and it was ~$400. Can't remember the exact model.

I am using a Toshiba and a Midea in the house. Toshiba must be a subsidiary of Midea because the Midea Smart Home app can recognize and control the Toshiba portable unit as well. I use the app to control the units remotely.

I have the Toshiba one of these (Just a rebadged Midea, even the app for it is Midea), barely made it a year... compressor went into a "death worble"

I use dry mode on my Toshiba unit daily and all the water is just expelled through the hose! It’s great because dry mode still cools in a sense and it uses way less energy based on my smart plug reading