# Thread: kWh for 20 Amps @ 208V

1. Web Hosting Master
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## kWh for 20 Amps @ 208V

I'm having a Monday morning here. Just want a double check

If we have a rack at pulling 20 Amps @ 208V for 30 days how many kWH is that.

I've got it as

20*208 = 4160 watts = 4.16 kW

720 Hours gives 2995 kWh

If we are charged \$0.10 per kWh (just for example here its not a real number)

That means we would have a bill of ~\$299.50/mo for power?

2. Temporarily Suspended
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Jan 2010
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If it is actually pulling 20 amps, approximately yes.
You would need a 30 amp breaker and 30 amp pdu to actually pull 20 amps
The utility may also have kW demand charges, and taxes, and etc etc.

Also, this doesn't account for the UPS overheads. Some data centers use a rule of thumb of doubling the raw utility power costs to cover the UPS, generator, power distribution, etc

3. Disabled
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Dec 2010
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The correct formula is
(volts x amps x power factor x phase x rated breaker)divided by 1,000

So it depends on the phase and rated breaker. The industry standard is 80% use of the rated breaker.

1 phase
208 x 20 x 1 x 1 x .80 / 1,000 = 3.328kw

3 phase
208 x 20 x 1 x square root of 3 x .80 /1,000 = 5.76kw

4. Backup Guru
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Your math is good, but keep in mind that for a 20A circuit, your continuous usage should not exceed 16A, so your bill should be lower.

5. Junior Guru
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Don't forget that the electricity usage will create heat, and thus, you will spend money to cool it as well.

6. Web Hosting Guru
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Cooling uses about 25% of actual power consumption. So, for every 10KW your environment is using, plan on using an additional 2.5KW for cooling. Of course this is 100% accurate and would depend on what systems you have in place / how efficient, and also ventilation - but if you are starting from scratch, hopefully this should give you some idea of what to expect.

7. New Member
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Cooling uses about 25% of actual power consumption. So, for every 10KW your environment is using, plan on using an additional 2.5KW for cooling. Of course this is 100% accurate and would depend on what systems you have in place / how efficient, and also ventilation - but if you are starting from scratch, hopefully this should give you some idea of what to expect.

8. THE Web Hosting Master
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