Billed Peak Increased After Install

We installed an 81kW grid tied array on a building. The usage of the building is primarily offices. After the installation, the peak that the power company measured is 4 times the previous peaks. This has been going on for a couple of months. The power company is in agreement that something doesn't make sense, but we haven't been able to resolve the issue. Any ideas or suggestions?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Billed Peak Increased After Install

    I'm not a grid-tie guy, but this seems to be a common problem with installs. The meter is wrong; it's counting the power sold back to the grid as usage. In other words, everything flowing through it, no matter which direction, is added up. Have the utility check the meter and make sure they've got the right one in there.

    Others may have different ideas.
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Billed Peak Increased After Install

    Just to be clear, is the new peak Watts or VA? And is the peak building consuming current or generating current? And is this a 15 minute peak or some sort of very short term peak (seconds)?

    It is very possible that the peak is a "generating" peak. The building may use power 24 hours x 7 (computer systems, A/C, etc.) but most of the solar power is generated in a 4-6 hour period. So if the array was intended to offset 100% of the building load, you would have the 24 hour load offset by ~6 hours of generation--About a 3-4x higher generation peak vs consumption peak.

    In California--this has been a big issue for some commercial sites... A San Diego school district stopped installations because their overall costs went up with solar (power+solar payments) because reservation (demand) charges went up rather than down--In California these charges are , very roughly, 1/2 of the typical commercial electrical bill (with kWH or kVA charges being the other 1/2).

    A couple of News Articles...

    -Bill

    As Marc says--check the meter(s) too... There have been rare occurances of misprogrammed electrical meters (new electronic meters for commercial buildings can be programmed to allow for bypass shunts for reporting kWH usage--i.e., the meter is across a bus bar/precision resistor that carries most of the current and the meter carries only a fraction---say for every 9 amps that flow through the bus bus bar, the meter carries 1 amp--so the meter would have a 10x factor between measured and displayed on meter face). [Vic corrects me--they are probably are current transformers rather than shunts as I had guessed]

    Also, many meters read one way and either do not read generated power, or read both loads and generated power as loads (excess power generated is shown as power consumed).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Billed Peak Increased After Install

    Mornin' Bill.

    You know every time you discuss that Orwellian nightmare of a billing system used in Calif. I wonder if anyone has taken a good look at it to see if it's of any benefit to anyone other than the utilities. I only mention it because of a recent survey by BC Hydro about a similar rate system change they've proposed. I'm debating doing a post about it; not sure how relevant it would be to the forum.
  • VicVic Solar Expert Posts: 3,112 ✭✭✭✭
    Re: Billed Peak Increased After Install

    As a bit of an aside,

    My shop building has a 400 Amp three phase service. It uses 200:1 Current Transformers. A new Stupid Meter was installed (no solar there), and is has read HI for 18 months. I complained that the useage was HIGH. PG&E, the utility, came out to test the meter, and said that it was OK.

    The meter has a factor of 40 -- registers 40 Kwh gulps. I have yet to get a reply from them to the question, "With this factor of 40, what should the CT ratio read?". They do not know, nor could they care. "there is no problem, go away, we are done!"

    I agree in general with BB Bill's observations ... It seems difficult to come out on a new Solar installation in CA, if for no other reason than the TOU Rate structure that is now being forced on the customer. Benefits the Utility (whatta surprise ?), not the customer.

    Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Billed Peak Increased After Install

    Marc,

    From my politics (which we do not discuss much here)--It is of benefit for the Government--It was never about "for the people"...

    There are many sides to the discussion... We have a split between commercial which is typically billed both for cost of copper/transformers/reserve power needs (demand) and actual kWH used (and sometimes on kVA used--I.e., Poor Power Factor for Motors, etc.). Which--from an engineering point of view is all very practical.

    Then we have from the late 1970's--Tiered pricing. The more power you use, the higher rates you are charged. The higher tier rates are used to subsidize smaller users.

    This is like going to the corner market to save money on your purchases instead of buying in bulk from the local MegaMart.

    But--that is changing a bit... They have finally had to reduce peak power rates and increase baseline tier rates (base rates had not increased in years).

    Much of California's interior valleys are heavy users of summer electricity (pumping and A/C). And they have been hit hard by the economic decline (and some other government water polices)... The high power rates do not help either.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Billed Peak Increased After Install

    Thanks for the replies. The peak is a kW measure. Although the peak measured on the meter is higher, the total usage is down as we would expect. The system was designed to support 15-20% of the building's total consumption.

    We've had the electric company technicians out to check the meters and they claim its all wired correctly. I've attached a line drawing of the schematic for reference.

    Any guidance we can provide to the electric company on how to diagnose the problem would help.
    Thanks.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,973 ✭✭✭
    Re: Billed Peak Increased After Install

    Sounds expected to me ....

    You new solar will increase the difference between your nominal and peak as measured by the power company.

    As your solar reduces your nominal levels, by a significant amount, whenever the solar drops out, say in partly cloudy weather, the difference is now not your building baseline load to its peak, but its baseline minus the solar assist which is a lowered value to peak.

    I know utilities have substantial surcharges on commercial accounts as typically, when a commercial account peaks, its much harder on the grid regulation to deal with than residential consumers.

    Solar isn't a good mix with this and one reason a CPA/MBA type is needed to run the numbers and see if solar pays-off as the peak charges dwarf the kWh charges the solar may save.

    Two guys and a truck might install a functional system for a commercial account but lack the end to end business review needed, this is a perfect example

    I can't say for sure from this keyboard if there isn't an issue, but it sure sounds like its working exactly as designed from where I sit

    PS:

    This is absolutely the wrong system to be using micro-inverters -- 219 inverters instead of one 100kw unit? That's a dead give-away on who did the install. I'm very surprised you got a permit for this as you have the issue of if you lose a phase , 2/3rds of micro inverter will continue to operate, there is no interlinking which is typically required for 3-Phase service. Your also unbalanced on the 3-Phase with 28 feeders.
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Billed Peak Increased After Install

    I assume they rewired the Meter Sockets (to add production meter). Do both meters read Peak KW (15 minute average?). What is the peak Production and peak Load readings? And you are sure it is Peak KW and not Peak KVA...

    A solar system has no where to "consume power"--and cannot produce much more than the Raw Solar Array ratings.

    And with the building, unless there has been a major change (A/C systems turned on for cooling season, brand new equipment, etc...

    Which leads me to question exactly how the utility (and your equipment on site) measure the Peak Power (or peak kVA). If it was measuring peak kVA per 3 phase leg (or 2 phase--Open Delta or something?)--I could see a problem with distribution/change of loads among phases during the rewiring, or possible some sort of wiring problem causing a phasing problem (poor power factor, bad phase angle)--Bad out of phase current would be the only way I could see a massive change in peak current loads (kVA vs KW) without putting the energy somewhere (work, heat, etc.). Also, at least in California, the peak kW/kVA is based on 15 minute average (I believe)--so a few seconds of motor starting should not send the peak usage way up.

    Otherwise, it leads back to a mis-wiring or mis-programming of the utility meter(s).... Do you have independent monitoring equipment that can confirm or deny the power company's readings?

    You may need to bring out a real power engineer on this one and have him connect some test gear. Again, out in California, that change in peak consumption could double the power bill--So I assume you are talking about some pretty serious money here.

    -Bill "not a power engineer" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Billed Peak Increased After Install

    From reading Solar Guppy's reply... Is your peak kW reading absolute or relative to average power consumption?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Billed Peak Increased After Install

    Bill, the peak is absolute not delta from nominal. I verified its reported at kW however I do not know what is going on inside the meter in terms of how it is measuring this. The actual value is not visible to us, the meter front only shows the kw-hr meter. We are looking for an independent measure of power but have not been successful in identifying someone local who either has the equipment or can install a monitor in place for the whole building.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,973 ✭✭✭
    Re: Billed Peak Increased After Install

    In my city is for sure delta, I know every location and power company has there own rules, but I would be very surprised if you power company is any different.

    It all comes back to why they even care about peak, and its simply that the grid has to balance generation to demand.

    Peak is to baseline and usually is in 15 minute intervals, solar lowers the baseline, but not necessary the peaks as generation is variable on the solar.

    I would suggest you compare past and present bills to get the answers on how peak is measured. peak from zero makes no sense, think about it, if you ran steady load at the billed peak value, no more peak which means it has to be delta

    I suspect your getting information from people that don't know how things actually work and are measured ( customer support, not engineers ).

    The solar installers should have run all this before a single panel was installed
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Billed Peak Increased After Install

    Out here in California, I believe that the demand/reservation number is an absolute peak... The lines and transformer needs to be large enough to supply their 15 minute peak power or kVA load any time based on last one year history.

    The kWH pricing is relatively low.

    -Bill

    By the way, the kWH charges are modified by time of use, seasonal, and tiered pricing... So there are still reasons to conserve.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭
    Re: Billed Peak Increased After Install

    In AZ for Residential This looks like it could hurt but the rates are way cheap if you can control your on peak.
    Combined Advantage 7 p.m. - Noon Rate Plan
    
    This plan may be best for you if:
    
    * You will generally use 1,000 kWh or more each month due to the size of your home and type 
      of appliances.
    * You are able to use more of your energy during off-peak hours, and can operate 
      your major electric appliances such as the water heater, pool pump and spa heater
      with a timer to run during off-peak hours.
    * You are able to use your dishwasher, dryer, washer, and range more during 
       off-peak hours.
    * You have a programmable thermostat or can set your air conditioning to a 
       warmer temperature during on-peak hours.
    * You are able to spread out your use of major appliances during on-peak hours, 
       so you are not using them simultaneously.
    
    Here's how it works:
    
    * The plan is billed on an off-peak and on-peak basis, with an on-peak demand component*.
      o Off-peak hours are weekdays from 7 p.m. to noon and all day Saturday and 
         Sunday, as well as six major holidays.
      o On-peak hours are Monday through Friday from noon to 7 p.m. and are 
         billed at a higher rate.
      o The demand is the one on-peak 60-minute period of the month when you use 
         the most electricity. It is also the largest component of the bill.
    * To save money, it is important for you to use more energy on weekends and 
       weekday mornings before noon or evenings after 7 p.m., since electricity used 
       during off-peak hours costs less. It is also important to limit the number of 
       appliances that you use at one time during on-peak hours.
    
    Winter (November - April billing cycles) 	                Cents per kWh
    On-peak kWh used (Mon. - Fri., noon - 7 p.m.) 	 $0.05815
    Off-peak kWh used (Mon. - Fri., 7 p.m.- noon and all day Sat. & Sun., 6 holidays) $0.04273
      	 Cost per kW Demand charge 	 $9.203
        	  
    Summer ( May - October billing cycles) 	              Cents per kWh
    On-peak kWh used (Mon. - Fri., noon - 7 p.m.) 	 $0.08845
    Off-peak kWh used (Mon. - Fri., 7 p.m.- noon and all day Sat. & Sun., 6 holidays) $0.04363
      	 Cost per kW Demand charge 	 $13.404
    

    And for a medium commercial account, I have no clue how that works!
    E-32 Medium Time-of-Use Plan (101 - 400 kW monthly)
    
    Here are the basic components of this rate plan:
    
        * A basic service charge for meter reading, account management, maintaining
          electric facilities and other general costs.
        * The cost of your actual energy use for the month (kWh). This amount goes 
           down as your use goes up - like a volume discount.
        * Cost of electricity is dependent on time of year.
    
    Basic Service Charge 
    Self-Contained Meters 	$ 0.672 per day
    Instrument-Rated Meters 	$1.324 per day
    Primary Voltage 	$ 3.415 per day
    
    Energy Charge 
    May – October Billing Cycles (Summer) 	       November - April Billing Cycles (Winter)
    For Secondary Service: 	For Secondary Service:
    $0.13261 per kWh for the first 5,000 kWh, plus 	$0.11512 per kWh for the first 5,000 kWh, plus
    $0.07251 per kWh for all additional kWh 	$0.05501 per kWh for all additional kWh
    For Primary Service: 	For Primary Service:
    $0.12939 per kWh for the first 5,000 kWh, plus 	$0.11189 per kWh for the first 5,000 kWh, plus
    $0.06929 per kWh for all additional kWh 	$0.05179 per kWh for all additional kWh
    
  • solarixsolarix Solar Expert Posts: 713 ✭✭
    Re: Billed Peak Increased After Install

    Here in Arizona the metered demand is measured as absolute. The average kW over any 15 minute period in a month is what costs you about $10/kW for commercial accounts unless it is less than 20kW which puts you in the "extra small" category which then you pay a "delivery charge" instead. Don't ask me how they figure that one. Have worked over many actual APS bills and never quite make them jive with the published rate plans.
    One really screwy thing I've encountered is some commercial plans have an energy charge that is say 12 cents/kW for the first 200kWH/kW and 6 cents per beyond that. In addition to being a negative tier which I believe they do to discourage solar, this 200kWH/kW is a sliding threshold so that the higher your peak demand is the more energy you have to pay the high rate on. If your demand is 30kW then you pay 12cents on the first 6000kWH. The real kicker is that in the published rate plans, they leave off the "per kW" part as it doesn't fit the form I guess - spent hours on the phone discovering that one let alone a person in the utility that could explain it. Like I said, many hours analyzing bills and rate plans - also why I don't use solar estimation software from out of state sources.
  • RCinFLARCinFLA Solar Expert Posts: 1,393 ✭✭✭✭
    Re: Billed Peak Increased After Install

    This is a learning experience for me.

    Why would you have a 3 phase building fed from a 2 phase drop feed?
    For that matter, what is a 2 phase drop? My guess is two single phase use drops.

    How does a three phase grid tie inverter, presumably without the 120 Hz pulsing power smoothing storage capability of single phase system, efficiently load PV panels when grid its feeding is not three phase?
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Billed Peak Increased After Install

    I am not sure regarding this installation--but one of the "interesting" things about 3 phase is you can use only two pole mounted transformers to supply 3 phase power (typically only done in with smaller 3 phase customers, as I understand--smaller may be 20 hp loads or less... getting out of my depth).

    Otherwise, 2 phase would typically be split phase power (120/240 VAC like in our homes).... There is no "easy way" (that I know of) to make 3 phase power from a 120/240 split phase (technically 2 phase where it is 180 degrees out of phase) with out using a motor generator, capacitors, or VFD type device.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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