If you are thinking of a cheaper option for room air conditioning then it will be better to opt for a room air conditioner. A room air conditioner is capable of cooling only one room. This unit is either installed in a window or in a wall opening. If you have a limited budget and can not afford a central air conditioner then room air conditioner would be a cheaper option. Though the cooling system can be installed at a cheaper price its running cost is comparatively higher as the air conditioner is not very efficient hence consume more energy for cooling a single room. There are energy efficient models now available in the market but may cost you more.
If you are living in a rented house then a room air conditioner will be a good choice as you can remove and reinstall the unit easily. You even get federal tax credits and subsidies while replacing old and energy consuming air conditioner with a new and energy efficient unit. It is true that the cost of installing an energy efficient room A/C can be high but on calculating the tax credit and the saving you are going to make out of its operating efficiency, you are going to make considerable savings within two years of its installation. You are going to receive a tax credit of up to $300 for an energy efficient unit in addition to this you will also be making an extra savings of $10 per month on energy bills hence around 400 dollars is what you will be saving the first year. So if you can manage to make the initial investment then you will only benefit out of it.