I was looking into buying one that was either gold or platinum certified but some people suggeseted i drop down to bronze in order to save money. What difference does the gold certification make? I thought it made the psu use less electricity thus making your whole pc use less power making it run more cheaply.
its all about the efficiency of the power supply to convert the amount of watts drawn from the wall into usable energy for the PC. For example, if a power supply has a 75% efficiency and it is drawing 1000W from the wall, it only delivers 750W worth of usable power to the PC, the extra 250W are wasted. So essentially the higher a psu's certification, the less power will be wasted in converting the raw power into usable power.
As for the ratings:
Bronze ~ 80%
Silver ~ 84%
Gold ~ 88%
Platinum ~ 92%
You do save money in the long run by using less energy, but platinum power supplys are expensive, while bronze is cheaper.
As far as I can tell (even with my limited brain functionality...), a Gold or Platinum makes more efficient use of your power
e.g 85% of your power travelling to your PC from your power supply is being used effienciently.
A higher rated PSU is making your pc safer.
However,it does depend on what components you are using.
More expensive the components, the more you should opt for a higher rated PSU.
(If i'm wrong, correct me. But from what i've seen, this is what i think about a rating)
I would like to add a few points to isteelsolz's answer,
The parts that are used in manufactufing the PSU are also different for Bronse, Silver, Gold. i.e Better parts for high priced product.
The chances of failure different for different types. i.e. Chance of failure for Bronse is more compared to Gold and Platinum.
Also if the AC mains Fluctuate, due to either some power failure, earth quake, zombies, volcano, tsunami, Logan :P... etc..etc..
The better rating power supply will be able to handle it better without frying your precious component.
I think you should meet in the middle grab silver :)
There aren't many silver rated PSUs on the market today compared to Bronze, Gold and even Platinum rated PSUs. It's mainly to do with price. The difference between both Silver and Gold was miniscule in some cases. The HX line from Corsair use to be silver. They're now rated at Gold.
Seasonic, Enermax, Rosewill, Corsair, XFX and few others actually make pretty good bronze rated PSUs aimed at the budget consumer. If you don't mind spending an extra few dollars on your electricity bill every couple of months, then they're still very good investments.
Bronze will be fine, its an effeciency thing, the Gold and Platnums will be good, but being Gold doesent mean it will deal with power flucuations or anything else better then the Bronze, just that whatever load your at it will be more effecient, the effeciency is usually in the capacitors and some other parts of the design, But the filtering stages and safeguards are usually the same in 80 plus Bronze to Gold and even Platinum PSU's
Most Bronze PSU's still have the over/under current and all the other protections, just make sure your PSU uses active PFC to handle the incoming voltage/current as that will make sure its able to handle imperfect voltages and current relatively well compared to legacy designs.