Tag: demand

Totalizing Meter Readings

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Totalizing meter readings can be a very effective way to lower your demand and KWH costs. So, if you are a commercial or industrial customer and have multiple meters you may benefit from totalizing your meter readings. What is totalizing? How can you benefit from totalizing? What are the different methods of totalizing?

What is totalizing?

Totalizing, at its simplest form is nothing more than addition. You take the meter readings from all of the meters that you have and you add them together. This, in turn, gives you one meter reading. Furthermore, it is much easier many times for the customer as they only have to keep up with one bill. A more advanced definition of totalizing is that by combining your meter readings the peak demand can be effectively reduced.

To explain this we need an example. Look at the picture below. In it you see that there are three lines. In this example we have meter A, B and totalized meter C. Also note that the numbers on the bottom are hours of the day. Here we are assuming that the demand interval is hourly. Notice that meter A peaks at 3:00 PM. The peak demand for meter A is 24 KW. Notice that the peak demand for meter B is also 24 KW but it occurs at 9:00 AM. If you do not remember how demand works go over to my page on demand for a better understanding.

.totalizing chart




Now that you have seen where meters A and B peak, let’s look at the totalizing meter C. Meter C peaks at 12:00 PM with a peak of 19.5 KW. This is 4.5 KW less than both meter A and meter B. This is because the totalizer effectively averages out all of its inputs. With KWH totalizing simply adds all of the KWH readings of the meters.

How can you benefit from totalizing?

Well, using the example above I am sure that you can see that your demand is reduced. So, let’s put that into dollars. Assume that your per KW demand charge is $15.00. For each meter that you have, A and B you will pay $360 each (24 KW x 15). So, for both meters you pay $720 per month just in demand charges. In addition, if you totalize with meter C your demand charges would only be $292.50 (19.5 KW x 15). A savings of $427.50! This is huge! However, remember that this is just an example, it is exaggerated.

You also save with your KWH charges. The reason for this is that most rates are tiered. Meaning that the price changes as you use more KWH. Also, in most cases the price goes down. If meter A uses 10,000 KWH in a month and meter B uses 15,000 KWH in month then in total they use 25,000 KWH. However, if the price buckets are as follows:

  • $0.10 for the first 5,000 KWH
  • $0.08 for the next 10,000 KWH
  • $0.06 for all over 15,000 KWH

then if your meters are billed separately you will not be able to take advantage of the cheaper rate bucket. If you totalize however you will be able to take advantage and save on your KWH as well.

What are the different methods of totalizing?

There are two main methods of totalizing. Totalizing with software is the first. Using hardware, such as the meter is the second. To totalize with software the utility downloads readings from each of the meters that are to be totalized. The utility then uploads the readings to a totalizing program. This program looks at all of the readings adds them together and averages them out. Then it gives you the totalized readings.

Using hardware to totalize is a bit different. Wires are run from the meters that need to be totalized. Then to a central meter that totalizes the readings internally. The utility then reads this totalized meter to get the readings. Finally, the utility bills the customer with the totalized readings.

Final Thoughts

Although it sounds like totalizing is definitely worth it you need to be aware that your utility may charge a premium to totalize your readings. This can vary and also may not be worth it. Instead of paying facility charges for the meters that you already have, you may pay for those and the totalizer. In addition, totalizing meters are expensive.

It is best to talk with your utility to determine if you are a good candidate for totalizing.








Meter Multipliers

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Watthour meter multipliers are used whenever current transformers and/or voltage transformers are used in a metering circuit. The most often question that I am asked about watthour meter multipliers is how to calculate the watthour meter multiplier. It really is a simple thing to do and this article will explain.

Current Transformers and Potential Transformers

CT’s and PT’s are used to step down current and voltage in a metering circuit to a safe and measurable level. But this leaves us with a little bit of math to do to accurately calculate the number of KWH or kilowatt hours the customer has used.

To calculate the meter multiplier we need to know what the CT ratio and PT ratio are. The best way to explain this is with an example.

Meter Multiplier Example 1

Let’s say for instance that you have a 120/208 three phase 4 wire wye service that is using 400/5 CTs.

How would you determine the watthour meter multiplier? You would simply do the math. 400/5 means 400 divided by 5 and if we do this math we come up with an answer of 80, this is our watthour meter multiplier. What if we had 600/5 CTs? 600 divided by 5 is 120, so our watthour meter multiplier is 120.




Now what if the service that we are metering is a 480v service and we are using PTs? For this example let’s assume we are metering a 480v three phase 4 wire wye service by using 400/5 CTs and 2.4/1 PTs. How do we come up with the watthour meter multiplier in this example? We would use the same method as before to find the CT ratio and do the math of 400 divided by 5 which equals 80 but we are not finished because in this example we also have PTs. Before we do the math let’s remember Ohms’s law which says that Watts = volts x amps. Let’s also remember what we are trying to figure out. We are trying to find the multiplier for the WATThour meter. So to find watts we need to multiply volts x amps. We already know the amps part of the equation equals 80 so what is the volts part? It is 2.4 because 2.4 divided by 1 is 2.4. So, we now multiply 80 x 2.4 and we come up with 192 which is our watthour meter multipler.

Meter Muliplier Example 2

Another example with PTs and CTs. Say you have a 480v three phase three wire service with 200/5 CTs and 4/1 PTs. What is the watthour meter multiplier? 200 divided by 5 equals 40. 4 divided by 1 equals 4. So, 40 x 4 = 160. Thus, the watthour meter multiplier would be 160.

When you divide out the CT ratio and PT ratio and multiply them together this is also known as the transformer factor.

Conclusion

So, there you have it.

To calculate watthour meter multipliers first you need to determine whether there are CTs and PTs or only CTs in the circuit. Next, divide out the ratios. And lastly, multiply the ratios to determine the watthour meter multiplier.