Calculate Electric cost?

Question

My tenant has a server with a dedicated A/C unit. It is a 2 phase circuit. It draws 14 amp average over an hour. Cost of electricity including taxes etc averages $.17/kwh. Both the server and the a/c run 24/7.
I have looked up formulas and asked some advice, but I consistently get an answers of a monthly cost of around $415/month or around $750/month. The confusion, I believe is whether or not the two phase service is relevant.

Thanks for any advice

Answer 1

It's not really 2-phase, the AC is running off a single-phase 230V line (to neutral, each line is 120V, but the load is connected phase-to-phase therefore it's considered single-phase)



14A * 230V = 3.22kW load. Times 24hr is 77.28kWhr/day, or times 30 is 2318kWhr/month. Times $0.17 is $394 per month.



....now, you said the AC is on 24/7, but I doubt if the compressor, which is the load, is actually running at 100% duty cycle. And if you really want to be accurate, perhaps your tenent could purchase his own watt-hour meter since power usage is variable through the day and the season.





Here's one that'll handle 230 split-phase for $260 -



http://www.powermeterstore.com/index.php?cPath=112&products_id=4124

Answer 2

For single phase, kWh = Hours X Volts X Amps X Power Factor / 1000



For three phase, kWh = Hours X Volts X Amps X Power Factor X SqRoot3 /1000



Measure current in one hot wire. Measure voltage between two hot wires or between hot wire in neutral for single phase with only one hot wire.



As far as I know, 2 phase requires 4 wires and is an obscure archaic system that has not been used for many years.



Power factor accounts for the magnetizing current of a motor that does not deliver power. It is between 0 and 1. If you can't measure it, you could assume 1 and be sure not to charge too little.

Answer 3

Since you do not mention the voltage the number of kilowatt hours cannot be calculated. Power =volts times current.