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[EnergyPlus_Support] Re: Economics and Demand Cost Calculations



What I am trying to do is figure out what portion of the utility bill is due to lighting, 
HVAC, process, etc. (a common question from clients).  The billing is simple: demand and 
consumption charges.  Since demand charges are by far the largest part of the bill, I 
wanted an easy way to split these charges amongst the various services.  If I understand 
you correctly, this isn't possible with the current version of EnergyPlus.

Most of what you said about submetered charges not adding up to the facility metered 
charges makes complete sense.  My mistake was that I wasn't thinking about the 
submeters as being actual meters.   Any time demand charges are involved, I would expect 
the sum of the submeters and facility meter to differ because the demand peaks on the 
various meters are not likely not be coincident.  Only if they were would I expect the two 
to be the same.

Thanks,
Greg

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" <mjwitte@...> wrote:
>
> I am not sure I understand what you are trying to do.  The energy and demand 
> charges within a given tariff will only be based on the specific meter or sub-
> meter that is assigned to that tariff.  If you want to calculate demand charges 
> for the building as a whole but then separate energy charges by end-use, you 
> would need a tariff connected to the facility electricity meter that calculates 
> only demand charges, and then tariffs connected to submeters that only 
> calcaulate energy charges.
> 
> Ultimately, I have to question your assumption that the submetered costs will 
> add up to the same value as the facility meter costs.  This will only be true 
> if the rates are a very simple single charge for energy and for demand, say 
> $0.10/kWh for energy and $15.00/kW for demand.  If there are any sort of 
> declining blocks or ratchets or other complexities to the rate structure, they 
> will not total to the same value.  The use of separate tariff objects in 
> EnergyPlus is intended to be used when the building truly has meters which are 
> separately billed, such as a separate meter for space-heating electricity.
> 
> Mike
> 
> 
> On 13 Aug 2007 at 18:31, boulder1259 wrote:
> 
> > I'm trying to figure out a way to apportion various building service costs but
> > am not having much luck.
> > 
> > When I sent up a tariff for facility-wide electricity charges (the charges
> > include demand charges), EnergyPlus seems to produce reasonable values. 
> > However, if I try to do the same for the various building services and then sum
> > them, the sum of the charges does not match the value of when I look at the
> > building as a whole.
> > 
> > I'm seeing that the electricity consumption charges can be summed, but that the
> > electricity demand charges cannot.  Apparently, the demand charges for the
> > individual services (e.g., lighting) are not calculated from the facility's
> > demand charges but rather independently.
> > 
> > Do you have suggestions of how to split the electric bill into its various parts
> > (e.g., lighting, pumps, fans, etc.)?
> > 
> > Thanks,
> > Greg
> > 
> > 
> > 
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> > 
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> > 
> > Attachments are not allowed -- please post any files to the appropriate folder
> > in the Files area of the Support Web Site.
> > 
> > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the
> > Documentation link and press the "search" button.
> > 
> > Yahoo! Groups Links
> > 
> > 
> > 
> > 
> >
>



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