The most expensive utility in vietnam is electric. In Danang, this can run two to four million vnd or more ($100 to $200 USD) per month during the hot months.
There are two ways of dealing with the high(er) cost of electricity in Danang. AC is the most expensive consumer of electricity. As much as eighty percent or more of your electric bill can be from the AC.
The Original Way
The original way of dealing with this was to open the doors and windows. Even today, you will see people taking their shoes off in front of the door in a way that prevents closing the door!
The advantages are many, you can live a comfortable life with some fans to blow the air. There are some fans that add a water element to cool the air as the fan blows. This has limited cooling because the greatest effect is in low humidity regions.
Aclimating
This can also mean changing your clothing to nylon and other synthetics rather than mostly cotton fabrics. Hoi An tailors will be happy to fit you and clothe you. I found custom pants for around 400.000 to 500.000 vnd. If you live on the ground level, you may also want to lower the mosquito population. This tennis racket shaped zapper is manually operated but extremely effective and satisfying and not very expensive at Lotte Mart.
The Western Way
On the other hand, if you have books, pillows, blankets and traditional western wear, you may need the AC to keep from getting everything moldy. Danang is a very humid climate, like Miami or Key West. Whether the temperature is hot or cold, high humidity in a closed space will make everything rot, mould, mildew or rust. This means keeping your closet doors open, etc.
This can become expensive if you are running the air conditioning. The alternative is a dehumidifier. You can find one in Danang or you can order one from Lazada. Dehumidifiers work well regardless of whether the outside temperature is hot or cold, they are slightly cheaper to run than air conditioning (more expensive than fans) with one slight disadvantage – they add a little heat.