I have a dell Inspiron 537 Slim-tower with 250 watts and I was wondering if and how I can find how many watts are free because I am planning to buy a new graphics card but do not want to fry my computer so if anyone knows how to find out how many watts I am using or how many I arnt using that would be GREATLY appreciated. Thanks
Check the side of your PSU, look at the amps on the +12V rail, multiply that number by 12, that is your actual useable wattage, then subtract the number that the outervision calculator gives you to find your available power.
Many OEM PSUs are just barely enough to run what they put in the system so if you want any significant GPU upgrade you are going to have to upgrade the PSU too. There are a few good slim line models from seasonic if you need to.
A lot is going to depend on the video card you want to install.
The general rule of thumb is a high quality 500 to 550 watt power supply with sufficient current (amps) on the +12 volt rail(s) can easily power a system with any single video card made. A high quality 700 to 750 watt power supply with sufficient current (amps) on the +12 volt rail(s) can power a system with two video cards operating in dual mode. There are a few exceptions like the new ATI Radeon HD 5XXX series cards which use less power due to their energy efficiency.
A high quality 500 to 550 watt psu will have a +12 volt rail rated at 40 amps. A high quality 700 to 750 watt psu will have a +12 volt rail rated at 60 amps.
In addition the power supply should be at least 80+ Bronze certified for energy efficiency. There are some models available which have achieved 80+ Silver and 80+ Gold Certifications.
Before purchasing a new psu you will need to decide whether you will eventually have a pc with one or two video cards.
Corsair and Seasonic are two brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Some of the newer models come with a 7 year warranty. Lately we've been seeing a few other brands offering some high quality units. One example would be the Antec Earthwatts and Antec TruePower New models which are a major improvement over Antec’s older psu’s like the Basiq models.