Antec EarthWatts 500 W Power Supply Review
By Gabriel Torres on February 18, 2008
EarthWatts is a series of power supplies from Antec with a Spartan look and relatively low cost, but able to deliver 80% efficiency and nominal power labeled at 50° C, also featuring active PFC and two video card connectors for your SLI or CrossFire setup. Let’s take an in-depth look inside the 500 W model and see if it can really deliver its labeled power.
On Figures 1 and 2 you have an overall look of EarthWatts 500 W. Its lack of any fancy finishing makes this power supply to resemble low-end “generic” models, but don’t let this fool you. This power supply is in fact a terrific product, as you will see during our review.
By the way, this is the power supply that comes with Antec Sonata III 500 case.
Even though it uses the traditional ATX layout with an 80 mm fan on its back it has a big mesh on its front side, improving airflow inside the power supply.
It features active PFC, a standard feature for high-end power supplies (you can see this by the absence of a 110/220 V switch, which isn’t present on power supplies with this feature). This feature provides a better usage of the power grid and allows this power supply to comply with the European law, making Antec able to sell it in that continent (you can read more about PFC on our Power Supply Tutorial).
Antec says this power supply has a minimum 80% efficiency. The higher the efficiency the better – an 80% efficiency means that 80% of the power pulled from the power grid will be converted in power on the power supply outputs and only 20% will be wasted. This translates into less consumption from the power grid (as less power needs to be pulled in order to generate the same amount of power on its outputs), meaning lower electricity bills – compare to less than 70% on regular power supplies.
And, as mentioned, this power supply is labeled at 50° C, so Antec guarantees that you will be able to extract 500 W from this power supply in the real world. Of course we will test this to see if it’s true.
This power supply comes with six peripheral power cables: two auxiliary power cables for video cards with 6-pin connectors, one cable containing three standard peripheral power connectors and one floppy disk drive power connector, one cable containing three standard peripheral connectors and two cables containing two SATA power connectors each.
We think that the number of connectors is more than perfect for the average user. High-end users will probably need more than four SATA connectors, but such users would buy a different kind of power supply anyway.
All the wires coming out from this power supply are 18 AWG, which is perfect for a power supply on this power range.
On the aesthetic side this power supply doesn’t have a nylon sleeving protecting all its wires, just the main motherboard wires.
We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.
In this page we will have an overll look, while in the next page we will discuss in details the quality and rating of the components used.
We can point out several differences between this power supply and a low-end (a.k.a. “generic”) one: the construction quality of the printed circuit board (PCB); the use of more components on the transient filtering stage; the active PFC circuitry; the power rating of all components; the design; etcetera.
As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components than that, usually removing the MOV, which is essential for cutting spikes coming from the power grid, and the first coil.
On this section this power supply is flawless, as it has more components than the necessary – one extra X capacitors, one extra coil and a ferrite bead on the main AC cable. It also provides one X capacitor and two Y capacitors after the rectifying bridge.
In the next page we will have a more detailed discussion about the components used in the EarthWatts 500 W.
We were very curious to check what components were chosen for the power section of this power supply and also how they were set together, i.e., the design used. We were willing to see if the components could really deliver the power announced by Antec.From all the specs provided on the databook of each component, we are more interested on the maximum continuous current parameter, given in ampères or amps for short. To find the maximum theoretical power capacity of the component in watts we need just to use the formula P = V x I, where P is power in watts, V is the voltage in volts and I is the current in ampères.
We also need to know under which temperature the component manufacturer measured the component maximum current (this piece of information is also found on the component databook). The higher the temperature, the lower current semiconductors can deliver. Currents given at temperatures lower than 50° C are no good, as temperatures below that don’t reflect the power supply real working conditions.
Keep in mind that this doesn’t mean that the power supply will deliver the maximum current rated for each component as the maximum power the power supply can deliver depends on other components used – like the transformer, coils, the PCB layout, the wire gauge and even the width of the printed circuit board traces – not only on the specs of the main components we are going to analyze.
For a better understanding of what we are talking here, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses one GBU806 rectifying bridge in its primary stage, which can deliver up to 8 A (rated at 100° C). This is more than adequate rating for a 500 W power supply. The reason why is that at 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.
The active PFC circuit from this power supply uses two FQH18N50V2 power MOSFET transistors, which are capable of delivering up to 20 A at 25° C or 12.7 at 100° C in continuous mode, or up to 80 A in pulse mode.
On the switching section other two FQH18N50V2 power MOSFET transistors in two-transistor forward configuration are used.
This power supply uses a CM6800 integrated circuit in its primary, which is a very popular active PFC and PWM controller combo. It is located on a small printed circuit board shown in Figure 10.
This power supply uses four Schottky rectfiers on its secondary.
The +12 V output is produced by two SBR30A50CT Schottky rectifiers connected in parallel, which can deliver up to 30 A each (15 A per internal diode, measured at 110° C). The maximum theoretical current the +12 V line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by two 15 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 43 A or 514 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.
The +5 V output is produced by one STPS30L30CT Schottky rectifier, which supports up to 30 A (15 A per internal diode, measured at 140° C). The maximum theoretical current the +5 V line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by one 15 A diode). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 21 A or 107 W for the +5 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.
The +3.3 V output is produced by another STPS30L30CT Schottky rectifier, which supports up to 30 A (15 A per internal diode, measured at 140° C). Using the same math this would translate into a maximum current of 21 A or 71 W.
Even though this power supply has a separated rectifier for the +3.3 V output, this rectifier is connected to the same transformer output as the +5 V line, so the maximum current +5 V and +3.3 V can pull together is limited by the transformer.
This power supply uses a semiconductor thermal sensor, which is very small and installed on the solder side of the printed circuit board, between the transformer and the +12 V rectifiers. This sensor is used to control the fan speed according to the power supply internal temperature.
On this power supply the active PFC capacitor is rated at 85° C, while the electrolytic capacitors from the secondary are rated at 105° C and are manufactured by OST, a Taiwanese company.
In Figure 13, you can see Earthwatts 500 W label stating all its power specs. As we have already mentioned, Antec labeled their power supply at 50° C (this information is on their website).
As you can see this power supply has two virtual rails, each one rated at 17 A. These rails are distributed as following:
We think that Antec made a good distribution for a two-rail product.
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology. All the tests described below were taken with a room temperature between 43° and 49.5° C. During our tests the power supply temperature was between 47° and 52° C.
Firs we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
+12V2 is the second +12V input of our load tester and on this test it was connected to the power supply EPS12V connector.
Since the power supply label states a 17 A limit for each rail and a 408 W maximum power for the +12 V output we kept these limits on our test number 5, so that’s why on this test you will see a current for +5 V and +3.3 V lines a little bit higher than what we would like to use. We, of course, pushed this power supply over its limits (the results are in the next page).
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
4 A (48 W)
8 A (96 W)
11 A (132 W)
14 A (168 W)
17 A (204 W)
3 A (36 W)
6 A (72 W)
10 A (120 W)
14 A (168 W)
17 A (204 W)
1 A (5 W)
2 A (10 W)
4 A (20 W)
6 A (30 W)
9 A (45 W)
1 A (3.3 W)
2 A (6.6 W)
4 A (13.2 W)
6 A (19.8 W)
9 A (29.7 W)
1 A (5 W)
1 A (5 W)
1.5 A (7.5 W)
2 A (10 W)
2.5 A (12.5 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.8 W (9.6 W)
% Max Load
Ripple and Noise
AC Power (1)
|AC Power (2)||121.8 W||227.3 W||350.3 W||480.6 W||616.0 W|
|AC Voltage||111.6 V||110.9 V||109.7 V||108.4 V||106.4 V|
Updated 06/25/2009: We re-tested this power supply using our new GWInstek GPM-8212 power meter, which is a precision instrument and provides accuracy of 0.2% and thus presenting the correct readings for AC power and efficiency (results marked as "2" on the table above; results marked as "1" were measured with our previous power meter from Brand Electronics, which isn't so precise as you can see). We also added the numbers for AC voltage during our tests, an important number as efficiency is directly proportional to AC voltage (the higher AC voltage is, the higher efficiency is). Also, manufacturers usually announce efficiency at 230 V, which usually inflates efficiency numbers. We added power factor (PF) numbers as well. These numbers measure the efficiency of the power supply active PFC circuit. This number should be as close to 1 as possible. Under light load (20% load, i.e., 100 W), the active PFC circuit from this unit isn't as good as when operating under higher loads, but 0.988 is still an outstanding number.
EarthWatts 500 W could really deliver 500 W at 47° C as promised by Antec, with a very high efficiency around 84-85% if you pull up to 60% of its maximum capacity (i.e., up to 300 W). At 80% load (400 W) efficiency dropped to 82.1%, still a good number. But at full load efficiency was 0.2% short of 80%.
All voltages were really stable, inside a 3% limit from the nominal voltage – which is really great, as the limit is 5% –, except the -12 V output. This output was at -11.02 V, -11.16 V, -11.31 V, -11.45 V and -11.48 V. Even though ATX12V standard sets -12 V tolerance at 10% (which means it can go from -10.80 V to -13.20 V) we would like to see it closer to the nominal -12 V voltage.
We were really impressed by the very low level of electrical noise produced by this power supply, the lowest we’ve seen to date. Noise on +12V1 input was between 13 and 14.6 mV on tests 1, 2 and 3, increasing to 18 mV on test 4 and 23.2 mV on test 5, hundreds of miles away from the 120 mV limit. Noise on +5 V line was between 7.4 mV and 9 mV during our tests, also far away from its 50 mV limit. Noise on +3.3 V was also very low on tests 1 through 4 (between 6.2 mV and 7.8 mV) but increased a lot on test 5 (19.2 mV), probably because we had to increase the current on this line more than usual, as explained at the beginning of this page. All these numbers are peak-to-peak values. Below we show the noise level we found on the power supply outputs while the unit was operating at its full load (test number five).
After these tests we tried to pull even more power from Antec EarthWatts 500 W. Below you can see the maximum amount of power we could extract from this unit keeping it working with its voltages and electrical noise level within the proper working range. During this test room temperature was of 46° C and the power supply was working at 47° C.
20 A (240 W)
20 A (240 W)
9 A (45 W)
9 A (29.7 W)
2.5 A (12.5 W)
0.8 A (9.6 W)
% Max Load
AC Power (1)
|AC Power (2)||714.0 W|
|AC Voltage||105.8 V|
Consider the results marked as "2", as they are the correct ones, measured with our precision power meter.
Here noise level increased just a little bit on the +12 V inputs, going to 26.2 mV on +12V1 and 25 mV on +12V2. These results are spectacular (the limit is 120 mV and any power supply capable of maintaining a noise level below 60 mV is a good product and we are talking about a power supply which noise level is almost five times lower than the limit). Noise on the other outputs remained the same.
We tried to pull even more power from the unit, but it wouldn’t turn on – showing us the over power protection (OPP) in action, which is great: it allows us to go over above the power supply limit but not high enough to the point where we would burn it.
On this unit over current protection (OCP) is disabled or is set at a value over 33 A. We made a simple test here, we set +12V1 at 5 A and then increased +12V2 to 33 A, and the power supply would work just fine. Since the label states a maximum current of 17 A per rail the power supply should not allow this.
Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.
During our tests we could see the speed of the power supply fan changing as the power supply temperature increased. Below 30° C it spun slowly, making almost no noise, and after this temperature it started increasing its speed, which also increased noise level. But even with it running at full speed it didn’t make a lot of noise.
Another interesting thing about this power supply is that it runs really cool. In fact it gave us a lot of work to increase the temperature inside our “hot box.” Even running at full load we had to wait more than 15 minutes until our “hot box” reached our minimum working temperature of 45° C. With high-end power supplies we can heat our hot box in just a few minutes.
Antec EarthWatts 500 W power supply specs include:ATX12V 2.2
* Researched at Shopping.com on the day we published this review.
Antec EarthWatts 500 W provides one of the best cost/benefit ratios for the average user: it is a relatively cheap 500 W power supply that can deliver up to 577 W at 46° C, has high efficiency (between 84% and 85% if you pull up to 300 W; 82.1% if you pull 400 W; but drops to 79.8% if you pull the full 500 W from it - it is clearly not a power supply to be working at 500 W but it is an excellent product for the average user with a mainstream PC), very low electrical noise level, is silent and provides two power cables for video cards. And it survived to our stress tests without burning.
It is an outstanding product and don’t let its simple look that reminds generic units fool you.
The number of cables provided by this power supply is more than enough for the average user, but users that need more than four SATA connectors will need another product or use adapters to convert the regular peripheral power plugs into SATA power plugs. But in our opinion this kind of user will look for a more high-end product anyway.
If you are a normal user that just want an honest power supply and don’t want to pay extra for a fancy paint job then this is the power supply you should buy.
Another option you have is buying Antec Sonata III 500 case, which costs around USD 120 and comes already with this power supply installed. This is an outstanding deal.