Patent Publication Number: US-8538586-B2

Title: HVAC control with utility time of day pricing support

Description:
TECHNICAL FIELD 
     The disclosure pertains generally to HVAC control, and more particularly, to HVAC control with utility time of day pricing support. 
     BACKGROUND 
     Heating, ventilation, and/or air conditioning (HVAC) systems are often used to control the comfort level within a building or other structure. Many HVAC systems include a controller that activates and deactivates one or more HVAC units or components of the HVAC system to affect and control one or more environmental conditions within the building. These environmental conditions can include, but are not limited to, temperature, humidity, and/or ventilation. In many cases, such an HVAC controller may include, or have access to, one or more sensors, and may use parameters provided by the one or more sensors to control the one or more HVAC components to achieve desired programmed or set environmental conditions. 
     An HVAC controller may be equipped with a user interface that allows a user to monitor and adjust the environmental conditions at one or more locations within the building. With more modern designs, the interface typically includes a display panel, such as a liquid crystal display panel, inset within a housing that contains a microprocessor as well as other components of the HVAC controller. In some designs, the user interface may permit the user to program the controller to activate on a certain schedule determined by the user. For example, the interface may include a routine that permits the user to change the temperature at one or more times during a particular day and/or group of days. Such a programmable schedule may help reduce energy consumption of the HVAC system by changing the setpoint to an energy saving set back temperature during certain times, such as when the building or space is expected to be unoccupied or when the occupants are expected to be sleeping. 
     Energy is supplied to most HVAC systems by one or more utilities, such as an electric utility and/or a gas utility. During peak demand periods, such as during hot summer days, such utilities may vary the rates that they charge for energy. Customers may wish to modify their energy consumption in response to these varying rates in order to reduce their energy bills. What would be desirable, therefore, is a new HVAC controller that can help customers modify their energy consumption during peak or anticipated peak demand periods. 
     SUMMARY 
     The disclosure relates generally to Heating, Ventilation, and Air Conditioning (HVAC) control, and more particularly, to HVAC control with utility time of day pricing support. 
     In some instances, control of an HVAC system may be modified based upon manually-entered utility pricing schedule information. In an illustrative but non-limiting example, a nominal schedule may be maintained in a memory of a local HVAC controller, where the nominal schedule has a number of days and one or more time periods for each of at least some of the days. The nominal schedule may also have at least one setpoint associated with each of the time periods. Manual input may be received via a user interface of the local HVAC controller. The manual input may include accepting entry of a utility pricing schedule that corresponds to scheduled price changes of a utility. The utility pricing schedule may include at least one enhanced pricing time period. Entry of at least one utility price level setpoint may also be accepted to correspond to each of the enhanced pricing time periods. The nominal schedule may then be modified or overridden to include the utility pricing schedule, resulting in a utility pricing operating schedule. One or more HVAC units may then be controlled by the local HVAC controller in accordance with the utility pricing operating schedule. 
     The above summary is not intended to describe each and every disclosed illustrative example or every implementation of the disclosure. The Description that follows more particularly exemplifies various illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The following description should be read with reference to the drawings. The drawings, which are not necessarily to scale, depict selected illustrative embodiments and are not intended to limit the scope of the disclosure. The disclosure may be more completely understood in consideration of the following description of various illustrative embodiments in connection with the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram showing an illustrative HVAC system  10  for conditioning the inside air of a building; 
         FIG. 2  is a flow diagram of an illustrative method for operating a utility-powered HVAC system including accepting entry via manual input of a utility pricing schedule; 
         FIG. 3  shows an illustrative example of an HVAC controller that may be used in an HVAC system like that of  FIG. 1  and that may be used to practice the method of  FIG. 2 ; 
         FIG. 4  shows the illustrative HVAC controller of  FIG. 3  configured to allow a user to disable or enable a utility pricing operating schedule; 
         FIG. 5  shows the illustrative HVAC controller of  FIG. 3  querying whether cooling temperatures are to be adjusted based on a utility pricing schedule; 
         FIG. 6  shows the illustrative HVAC controller of  FIG. 3  querying whether different seasonal pricing exists for a utility pricing schedule. 
         FIG. 7  shows the illustrative HVAC controller of  FIG. 3  configured to allow entry of a number of utility price levels; 
         FIG. 8  shows the illustrative HVAC controller of  FIG. 3  configured for entry of a utility pricing level setpoint; 
         FIG. 9  shows the illustrative HVAC controller of  FIG. 3  configured to accept entry of a seasonal start date of a utility pricing schedule; 
         FIG. 10  shows the illustrative HVAC controller of  FIG. 3  configured to accept selection of days of the week for inclusion in a group of days for a utility pricing schedule; 
         FIG. 11  shows the illustrative HVAC controller of  FIG. 3  querying whether there are any utility price level changes during a day; 
         FIG. 12  shows the illustrative HVAC controller of  FIG. 3  querying for when a first price change is to occur; 
         FIG. 13  shows the illustrative HVAC controller of  FIG. 3  showing the currently set temperature setpoint limits for various price levels; 
         FIG. 14  is a flow diagram of another illustrative method for operating a utility-powered HVAC system including accepting entry via manual input of a utility pricing schedule; 
         FIG. 15  shows another illustrative HVAC controller that may be used in an HVAC system like that of  FIG. 1 , configured in a nominal schedule review/edit mode; 
         FIG. 16  shows the illustrative HVAC controller of  FIG. 15  displaying heating and cooling setpoints of a nominal schedule in a graphical format; 
         FIG. 17  shows the illustrative HVAC controller of  FIG. 15  configured to allow entry of a utility price level setpoint offset; 
         FIG. 18  shows the illustrative HVAC controller of  FIG. 15  displaying a summary of parameters for an enhanced pricing time period; 
         FIG. 19  shows the illustrative HVAC controller of  FIG. 15  displaying heating and cooling operating setpoints of a utility pricing operating schedule in a graphical format; 
         FIG. 20  shows another illustrative HVAC controller displaying heating and cooling operating setpoints of a utility pricing operating schedule in a graphical format; and 
         FIG. 21  is a flow diagram of another illustrative method for operating a utility-powered HVAC system including predicting a Critical Peak Pricing event. 
     
    
    
     DESCRIPTION 
     The following description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected illustrative embodiments and are not intended to limit the scope of the invention. Although examples of construction, dimensions, and materials are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized. 
       FIG. 1  is a schematic diagram showing an illustrative HVAC system  10  for conditioning the inside air of a building. The methods and devices of the present disclosure may be practiced with HVAC system  10  and/or as part of HVAC system  10 , but they are not limited to HVAC systems. It is contemplated that the methods and devices of the present disclosure may be practiced with other systems, such as water heating systems, lighting systems, manufacturing systems, sprinkler systems, etc. For convenience, an HVAC system  10  is used as an example below. 
     The illustrative HVAC system  10  of  FIG. 1  includes an HVAC controller  12 , which may be a thermostat, and may be configured to interact with and control HVAC equipment  14 . HVAC controller  12  may be a local HVAC controller, located in the building that is conditioned by the HVAC equipment  14 , or in close proximity to the building, such as within a complex of neighboring buildings. HVAC equipment  14  may include, for example, one or more of cooling unit  16 , heating unit  18  and/or ventilation unit  20 . HVAC equipment  14  may include other units such as a humidifier unit, a dehumidifier unit, a UV filter unit and/or any other suitable HVAC unit. In some cases, cooling unit  16  and heating unit  18  may, for example, be combined in a forced air system, or perhaps a heat pump system, particularly in residential and/or light commercial applications. In other cases, one or more of cooling unit  16 , heating unit  18  and/or ventilation unit  20  may be distinct systems controlled, either directly or indirectly, by HVAC controller  12 . In some instances, it is contemplated that HVAC controller  12  may represent two or more distinct controllers, each controlling different equipment within HVAC equipment  14 , and/or different zones within a structure. 
     HVAC controller  12  may include any suitable components related to effecting control of the HVAC system  10 . For example, HVAC controller  12  may include a user interface  32 . The user interface  32  may include one or more displays and/or buttons that a user may interact with. In some instances, a touchscreen display may be provided. In the illustrative embodiment, HVAC controller  12  includes a processor  34 , which may be a microprocessor, and a memory  36  which may be used to store any appropriate information such as HVAC control routines or code, historical performance data, HVAC system parameters, one or more programmable schedules for changing HVAC system parameters over time, and so on. HVAC system parameters may include setpoints for heating, cooling, humidity, etc., modes for ventilation equipment, fan settings, and the like. 
     As shown, HVAC controller  12  may include one or more sensors, such as an internal sensor  38  located within a housing  42  of the HVAC controller  12 , and/or external sensors  40 , which may be located external to the controller housing  42 . The external sensors  40  may be within the building and/or outside the building, as desired. HVAC controller  12  may include one or more outputs  44  configured to issue operation commands to HVAC equipment  14  and units  16 ,  18 ,  20 . 
     One or more utilities  22  may provide energy to the HVAC system  10 , including HVAC equipment  14 . The utility or utilities  22  may supply a source of energy such as electricity, natural gas, hot water, steam, and/or any other suitable sources of energy. In order to help reduce peak loads, utilities are increasingly employing variable pricing schemes. Any number of pricing (rate) schemes may be employed. For example, energy rates may be raised during an enhanced pricing time period during the day compared to at night, due to higher anticipated demand for industrial and commercial use and/or greater demand for cooling during daylight hours. Any appropriate number of rate changes may be made during a day, such as a mid-tier or mid-peak rate becoming effective at the start of the work day, then a higher-tier or higher-peak rate becoming effective for the greatest temperature period later in the day when air conditioning loads are usually highest, then returning to a non-peak rate after the work day ends. In some arrangements, enhanced pricing time periods may recur on a daily basis, or they may recur daily within a group of days such as weekdays, with different rate schedules being effective on other groups of days such as weekends. In some cases, enhanced pricing time periods of a utility may recur on a weekly basis. 
     Schedules for recurrences of enhanced pricing time periods may vary over longer time intervals, such as between seasons. For example, a summer schedule for weekly recurrences of enhanced pricing time periods may be in force during warmer months of the year, and a different winter schedule may be in effect for colder months. 
     Utilities may plan and communicate schedules for rate/price changes well in advance of the dates for such changes. For example, summer and winter enhanced pricing rate schedules may be determined long before the in-force dates for the schedules. In other situations, enhanced pricing time periods may be declared and/or scheduled on shorter time scales, such as in response to a heat wave or a cold snap (periods of relatively extreme environmental temperatures), or even due to an unforeseen cause such as failure of a power generation facility or an international crisis that constrains energy supplies. In some situations a utility may enact an enhanced pricing time period of Critical Peak Pricing (CPP) with short notice (for example announcing a CPP event one day in advance), for example in response to actual or anticipated very high demand for energy. 
     In response to higher rates during enhanced pricing time periods, customers may desire to curtail energy consumption (and hence, demand on the utility) relative to consumption during periods of normal or nominal pricing. This may be accomplished by, for example, temporarily setting less comfortable setpoints. Generally speaking, a demand-side response to enhanced pricing may be achieved in a number of ways. A homeowner with a simple non-programmable thermostat may manually adjust the thermostat setpoint in response to rate changes. This approach may be relatively labor intensive and require substantial diligence on the part of the homeowner. In a more sophisticated approach, a local HVAC controller such as a thermostat may be configured to receive automated signals from a utility (such as via a wired and/or radio-frequency communication link) that communicate enhanced pricing information, and the HVAC controller may be configured to adjust HVAC system operation in a predetermined response to price changes without the need for immediate user action and/or awareness. Aspects of such a system are disclosed in, for example, U.S. Pat. No. 6,574,581, “PROFILE BASED METHOD FOR DERIVING A TEMPERATURE SETPOINT USING A ‘DELTA’ BASED ON CROSS-INDEXING A RECEIVED PRICE-POINT LEVEL SIGNAL,” Bohrer, et al., which is hereby incorporated by reference in its entirety. 
     In one illustrative embodiment, the present disclosure provides methods and devices that assist utility customers in modifying HVAC system operation and energy consumption in view of rates changes of utilities during enhanced pricing time periods, without necessarily requiring an automated communication link between a utility and the HVAC system controller. In some instances, methods and devices are described that allow for manual entry of pricing schedule information into an HVAC controller. In other instances, methods and devices are described that allow an HVAC controller to predict Critical Peak Pricing (CPP) events, and control an HVAC system to modify energy consumption during the predicted CPP event time periods. 
       FIG. 2  is a flow diagram of an illustrative method  200  for operating a utility-powered HVAC system, such as system  10  of  FIG. 1 . In block  202  a local HVAC controller may maintain in its memory a nominal schedule that is used to control the HVAC system during non-enhanced pricing periods. The nominal schedule may represent the normal programmable schedule of a programmable thermostat. The nominal schedule may, for example, be a 7 day programmable schedule (where each of the seven days of the week can have a separate schedule), a 5-2 programmable schedule (where the five week days have a common schedule, and the two weekend days have a common schedule), or any other schedule. 
     In some cases, the nominal schedule may have a number of days and one or more time periods for each of at least some of the days. In some instances, the nominal schedule may include a “sleep,” a “wake,” a “leave,” and a “return” time period for each of the days of a week. The nominal schedule may have at least one setpoint associated with each of the one or more time periods. The nominal schedule may be maintained in the local HVAC controller&#39;s memory, and typically may be modified by an end user. The nominal schedule may be programmed using an interface such as one of those disclosed in U.S. Pat. No. 7,114,554, “CONTROLLER INTERFACE WITH MULTIPLE DAY PROGRAMMING,” Bergman et al., which is hereby incorporated by reference in its entirety. 
     Method  200  includes receiving manual input via the user interface of the local HVAC controller. At block  204 , it includes accepting entry of a utility pricing schedule that corresponds to scheduled price changes of a utility, including at least one enhanced pricing time period. In some illustrative embodiments, the utility pricing schedule is provided to the user by the utility. For example, the utility pricing schedule may be provided along with a monthly statement/bill, published in a newspaper, sent via electronic messaging such as in an email message or text message, made available on a website, and so on. In some illustrative embodiments, the utility pricing schedule may include at least one recurring enhanced pricing time period, which may recur weekly. In some illustrative embodiments, the utility pricing schedule may include at least two seasons, and enhanced pricing time periods may correspond to one of the seasons. At block  206 , method  200  includes accepting entry of utility price level setpoints to correspond to each of the enhanced pricing time periods of block  204 . Such setpoints may be chosen with the goal of reducing energy consumption (relative to the nominal schedule) during an enhanced pricing time period, often at the expense of comfort. More than one utility price level setpoint may be entered for each enhanced pricing time period. For example, there may be two, one for cooling and one for heating. In some illustrative embodiments, further setpoints may be entered. For example, different utility price level setpoints may be entered depending on whether an enhanced pricing time period occurs during an occupied period vs. an unoccupied period of the nominal schedule. Aspects of user interfaces that may be used to accept entry via manual input from a user of utility pricing schedules and utility price level setpoints are described in further detail elsewhere herein. Such disclosed user interface elements may be considered as extensions of the method  200  of  FIG. 2 . 
     Method  200  further includes at block  208 , modifying or overriding the nominal schedule to include the utility pricing schedule entered at block  204  to result in a utility pricing operating schedule. In some illustrative embodiments, the utility pricing operating schedule may include time periods of the nominal schedule and setpoints associated with the time periods of the nominal schedule, except that during enhanced pricing time periods of the utility pricing schedule entered at block  204 , during which the utility price level setpoints corresponding to the enhanced pricing time periods are in effect. At any given time, there may be only one setpoint in effect, which may be referred to as an operating setpoint, depending on the current mode (e.g., heating or cooling), season, time period, utility price level, and/or any other relevant HVAC or utility parameter. 
     In some illustrative embodiments, the step  208  of modifying or overriding the nominal schedule to include the utility pricing schedule may be performed such that the current operating setpoint at any or every given time during each of the enhanced pricing time periods is chosen to result in greatest economy, consistent with the current mode (heating or cooling) of the HVAC system. This may result in the current operating setpoint being either the utility pricing level setpoint for the current enhanced pricing time period, or the setpoint of the nominal schedule, whichever is most economical. The following non-limiting example may elucidate this setpoint selection condition: During the cooling season, an enhanced pricing time period from 8:00 am to 5:00 pm has a utility price level setpoint of 82° F. Prior to 8:00 am, the nominal “wake” time period setpoint is 78° F., so prior to 8:00 am, the current operating setpoint is 78° F. At 8:00 am, the enhanced pricing time period commences, and the current operating setpoint changes to the utility price level setpoint of 82° F., which is more economical than 78° F. At 8:30 am, the nominal schedule switches from “wake” to “leave,” for which the nominal setpoint is 85° F. Thus, at 8:30 am, the current operating setpoint changes to the nominal “leave” setpoint of 85° F., which is more economical than the utility price level setpoint of 82° F. of the current enhanced pricing time period. At 4:00 pm, the nominal schedule switches from “leave” to “return,” for which the nominal setpoint is 78° F. Now the utility price level setpoint of 82° F., being more economical than 78° F., is the current operating setpoint. At 5:00 pm, when the enhanced pricing time period ends, the nominal “return” setpoint of 78° F. becomes the current operating setpoint. 
     The immediately preceding example also illustrates a procedure for determining current operating setpoints that may be practiced in some illustrative embodiments. At every start time of either a time period of the nominal schedule or a enhanced pricing time period, a comparison may be made between the setpoint of the current time period of the nominal schedule (for the current mode, either heating or cooling) and the utility price level setpoint (heating or cooling) corresponding to the current enhanced pricing time period. From that comparison, the most economical setpoint is selected as the current operating setpoint at that start time. Note that in this method, the utility price level “setpoints” may also be regarded as “setpoint limits,” in that they provide a limit to how much cooling or heating will be provided during enhanced pricing time periods. 
     At block  210 , the method  200  includes controlling one or more HVAC units of the HVAC system with the local HVAC controller in accordance with the utility pricing operating schedule of block  208 . 
     In some illustrative embodiments of a method, like method  200  for operating a utility-powered HVAC system, each schedule price change of a utility may be associated with a utility price level, such as Off-Peak, Mid-Peak, High-Peak, etc., such that each enhanced pricing time period has an associated or corresponding enhanced utility price level (and non-enhanced pricing time periods may correspond to, for example, an Off-Peak utility price level). Furthermore, at least one utility price level setpoint may be entered, defined, or otherwise set to associate with or correspond to each of the utility price levels. For example, a cooling utility price level setpoint of 85° F. and a heating utility price level setpoint of 62° F. may be entered and associated with Mid-Peak pricing, and setpoints of 90° F. (cooling) and 57° F. (heating) may be entered and associated with High-Peak pricing. 
       FIGS. 3-13  show an illustrative but non-limiting example of an HVAC controller  300  that may be similar to HVAC controller  12  of  FIG. 1 . HVAC controller  300 , which may be a thermostat, may be used to practice methods of the present disclosure, including method  200  of  FIG. 2 , and/or other appropriate methods. Furthermore, descriptions herein of user interface elements of HVAC controller  300  may be considered to extend method  200  and other methods of the present disclosure where they are compatible. 
     As shown, HVAC controller  300  may include a housing  302  and a display  304 . Display  304  may be a touchscreen display, and it may be a liquid crystal display (LCD), although neither of these are required.  FIG. 3  shows HVAC controller  300  with a default “home” screen presented on display  304 . Buttons, such as HOME button  306  and FAN button  308 , may be shown on touchscreen display  304 . In some other illustrative embodiments, an HVAC controller may include one or more physical buttons, in some cases associated with labels on a display (as with so-called “soft” buttons), and/or in some cases with dedicated functions. More generally, it is contemplated that any suitable user interface may be used, as desired. 
       FIG. 4  shows the illustrative HVAC controller of  FIG. 3  configured to allow a user to disable or enable a utility pricing operating schedule, such as the utility pricing operating schedule of method  200 . When disabled, the HVAC controller  300  may control one or more HVAC units of an HVAC system in accordance with the nominal schedule of method  200 . When enabled, the HVAC controller  300  may control one or more HVAC units of an HVAC system in accordance with the utility pricing operating schedule of method  200 . 
     When the use of a utility pricing operating schedule is enables via the screen shown in  FIG. 4 , the user interface may follow by prompting and allowing entry of other parameters relating to the use of the utility pricing operating schedule. For example, if the user selects the “Next” button in  FIG. 4 , the HVAC controller  300  may advance to the screen shown in  FIG. 5 .  FIG. 5  shows the illustrative HVAC controller  300  querying whether cooling temperatures are to be adjusted based on a utility pricing schedule. The user interface may similarly allow a user to select whether heating temperatures are to be adjusted based on a utility pricing schedule (not shown). Subsequent prompts by and entries into the user interface may be scripted based upon user inputs, such as in response to these and other queries.  FIG. 6  shows another query that may allow the user interface to tailor later prompts to a particular utility scheduling scenario, in this case determining whether different seasonal pricing exists for a utility pricing schedule. 
       FIG. 7  shows the user interface configured to allow entry of a number of utility price levels or tiers in a utility pricing schedule. A utility pricing schedule may have two (for example, Off-Peak and High Peak), three (Off-Peak, Mid-Peak, and High-Peak, as shown), four (Off-Peak, Low-Peak, Mid-Peak, and High-Peak), or any other appropriate number of utility price levels. In  FIG. 8 , the user interface is shown configured for entry or setting of a utility pricing level setpoint. In the case shown, a cooling setpoint is being entered to correspond to or associate with the Mid-Peak utility price level, and accordingly, corresponds to or is associated with enhanced pricing time periods associated with the Mid-Peak utility price level. Similar user interface displays may be used for entry or setting of heating setpoints, and for other utility price levels (e.g., Low-Peak and High-Peak). In some illustrative embodiments, other appropriate HVAC parameters may be entered and associated with utility pricing levels, such as humidity setpoints, fan settings, etc. 
     In  FIG. 9 , the user interface is shown configured to accept entry of a seasonal start date of a utility pricing schedule. A similar user interface may be used to accept entry of other relevant dates for a utility pricing schedule. In  FIG. 10 , the user interface is shown configured to accept selection of days of the week for inclusion in a group of days, where enhanced pricing time periods will recur each day of the group of days, and also weekly on those days during the season the enhanced pricing time periods are associated with or correspond to (in this case, Summer). 
       FIG. 11  shows the user interface querying whether there are any utility price level changes (from a nominal Off-Peak price level) during a day. After selection of “Yes,” the user interface moves on, as shown in  FIG. 12 , to allow entry of the time of the first scheduled price change and the utility price level at that time. After this entry is completed, the user interface may query whether there is a subsequent utility price level change (similarly to that shown in  FIG. 11 ), and if so, allow entry of the time of the subsequent price change and the utility price level at that time (similarly to that shown in  FIG. 12 ). This process may repeat until all utility price level changes during the day have been entered. 
     After the utility price level changes for the days in a group of days selected in  FIG. 10  have been entered, the user interface may allow a user to schedule utility price level changes for other days that may form one or more other groups of days, using the same or similar user interface elements shown in  FIGS. 10-12 , and also for days and/or groups of days during other seasons. The user interface may also allow review of a utility pricing schedule.  FIG. 13  shows a screen from which a user may review and/or edit utility pricing schedule and utility price level setpoints. 
     Other user interface arrangements are possible. For example, after entry of a scheduled price change as in  FIG. 12 , rather than querying whether there is a subsequent utility price level change to enter, the user interface may be configured such that it queries for the total number of price changes per day at the outset before it accepts entry of parameters for any of the scheduled price changes. After accepting entry of the total number of price changes, the user interface could then prompt for and accept entry of the first price change, second price change, etc. Many user interface variations are contemplated for entry of utility price schedules. 
     In some illustrative embodiments, the utility pricing operating schedule may only include time periods and setpoints defined either in the nominal schedule or those entered as part of a utility pricing schedule, such as in blocks  204  and  206  of method  200 . However, in some illustrative embodiments, the utility pricing operating schedule may include time periods and setpoints other than those in the nominal schedule or those entered in blocks  204  and  206 , if desired. In some illustrative embodiments, for example, a utility pricing operating schedule may include a pre-cooling time period (in a season or on a day when HVAC cooling is desired; analogously, a pre-heating time period for when HVAC heating is desired). A pre-cooling time period may be scheduled before an enhanced pricing time period, when rates are lower than during the subsequent enhanced pricing time period, and in some cases, may include a cooler setpoint than normally would be controlled-to (at that time) according to the nominal schedule. The use of pre-cooling may allow greater comfort to be achieved during enhanced pricing time periods while still reducing energy consumption during the enhanced pricing time periods. An HVAC controller such as HVAC controller  12  of  FIG. 1  may be configured to incorporate pre-cooling into a utility pricing operating schedule. In some cases, pre-cooling may be offered as an option that is selectable by, for example, an end user or an HVAC technician. Parameters for pre-cooling may be selected or otherwise determined in any suitable way. For example, parameters for pre-cooling may be user selectable via the user interface. Such parameters may include pre-cooling temperature limits or bounds, time parameters for pre-cooling time periods, and/or any other appropriate parameters. In some illustrative embodiments, an end user may simply enter a preference whether or not to use pre-cooling, and if pre-cooling is desired, the HVAC controller may be configured to add one or more pre-cooling time periods to a utility pricing operating schedule without further user input. 
     The present disclosure contemplates additional ways for obtaining utility pricing operating schedules from modification of nominal schedules. For example,  FIG. 14  is a flow diagram of another illustrative method  400  for operating a utility-powered HVAC system, including accepting entry via manual input of a utility pricing schedule. Method  400  is similar in many ways to method  200  of  FIG. 2 , and substantial portions of the description of method  200  are relevant to method  400 . These include the discussions regarding maintaining a nominal schedule in memory of an HVAC controller at  202  and  402 , and accepting entry of a utility pricing schedule at  204  and  404 . 
     Method  400  differs from method  200  at block  406 , where method  400  includes accepting entry of utility price level setpoint offsets that correspond to the enhanced pricing time periods entered at step  404 . Generally, setpoint offsets may be combined with (added to or subtracted from) a first setpoint to result in a second setpoint. At block  408 , setpoint offsets entered at block  406  may be used in the step of modifying or overlaying the nominal schedule to include the setpoint offsets, resulting in a utility pricing operating schedule. 
     In some illustrative embodiments, operating setpoints for a utility pricing operating schedule may be obtained by the following method: When there is no enhanced pricing time period in effect, a setpoint of the current time period of the nominal schedule may be used as the operating setpoint. During an enhanced pricing time period (e.g. when the current time period of the nominal schedule overlaps with the enhanced pricing time period), a utility price level setpoint offset may be added to the current setpoint of the nominal schedule, resulting in a new operating setpoint. To further elucidate this method, an example is discussed elsewhere herein in connection with  FIGS. 15-19 . Method  400  continues at block  410  by controlling one or more HVAC units with the local HVAC controller in accordance with the utility pricing operating schedule. 
       FIGS. 15-19  show an illustrative but non-limiting example of an HVAC controller  500 . HVAC controller  500 , which may be a thermostat, may be used to practice methods of the present disclosure, including method  400  of  FIG. 14 , and/or other appropriate methods. HVAC controller  500  may be essentially the same as HVAC controller  300  of  FIGS. 3-13 , and may be able to practice method  200  of  FIG. 2  as well as method  400  of  FIG. 4 , if desired. Furthermore, either of HVAC controllers  300  and  500  may be reconfigurable to practice different or new methods, such as via a software update, software activation, or any other suitable reconfiguration method. 
       FIG. 15  shows the user interface of HVAC controller  500  configured in a nominal schedule review and edit mode, as may be practiced in an HVAC control method of the present disclosure. HVAC parameters for WAKE, LEAVE, RETURN, and SLEEP time periods are shown.  FIG. 16  shows the user interface displaying heating (bottom trace  502 ) and cooling (top trace  504 ) setpoints for the time periods of  FIG. 15  graphically in a 24 hour time interval. 
       FIGS. 17-19  particularly illustrate aspects of method  400  of  FIG. 14 . For example,  FIG. 17  shows the user interface configured to accept entry of a cooling utility price level setpoint offset for an enhanced pricing time period.  FIG. 18  shows the user interface displaying a summary of parameters for an enhanced pricing time period. In this example, for the sake of simplicity and without loss of generality, there is a single enhanced pricing time period for weekdays from 10:00 am to 7:00 pm. In general, an arbitrary number of enhanced pricing time periods may be scheduled.  FIG. 19  shows the user interface displaying heating  506  and cooling  508  operating setpoints of a utility pricing operating schedule, with offsets applied. For example, during the enhanced pricing time period  510 , from 10:00 am to 7:00 pm, the operating setpoints  506 ,  508  are seen to be offset by +5° F. for cooling and −3° F. for heating, per the parameters set in  FIG. 18 , and in comparison with the setpoints  502 ,  504  of the nominal schedule shown in  FIG. 16 . Note that at 5:30 pm (marked at  512 ), when the nominal schedule changes from “LEAVE” to “RETURN,” the offset operating setpoints  506 ,  508  change as they follow (with offsets) the changing setpoints  502 ,  504  of the nominal schedule. 
     In comparison,  FIG. 20  shows another illustrative HVAC controller  600  displaying heating and cooling operating setpoints of a utility pricing operating schedule in a graphical format. In this example, for the sake of simplicity and without loss of generality, there is a single enhanced pricing time period  610  for weekdays from 10:00 am to 7:00 pm with a heating utility price level setpoint of 55° F. and a cooling utility price level setpoint of 90° F. The nominal schedule underlying the utility pricing operating schedule in this example is the same as the nominal schedule of the example of  FIGS. 15-19 , but during enhanced pricing time period  610 , the setpoints of the nominal schedule are irrelevant and overridden by the heating and cooling utility price level setpoints (and not merely by an offset). 
     The present disclosure contemplates further avenues for entering a utility pricing schedule into an HVAC controller. An HVAC controller may include a capability for interfacing with information storage media or devices, such as flash memory devices having any suitable interface, such as Universal Serial Bus (USB), SD and SD variants, and so on. Such an information storage device may be used to enter a utility pricing schedule into an HVAC controller that is configured to accept the schedule from the device. An information storage device with a utility pricing schedule could be provided directly from utility, or a utility pricing schedule could be written to an information storage device by an HVAC system user. The user could, for example, download an electronic file encoding a utility pricing schedule via an information network such as the internet to a desktop, laptop, or any other appropriate computer or computing device, then write the file on the local computer to an information storage device, such as a flash memory device. Alternately, a computer or computer device may be communicatively connected to an HVAC controller via a wired, wireless, optical, or other type of connection, allowing transfer of a utility pricing schedule to the HVAC controller. Alternately or in addition, the computer could execute application code providing a utility pricing schedule editor (which may be considered an element of the user interface of the HVAC controller) that could write an electronic file encoding a utility pricing schedule to an information storage device. The utility pricing schedule may include enhanced pricing time periods and utility pricing levels associated with the periods. It may or may not further include utility pricing level setpoints and/or setpoint offsets corresponding to and/or associated with the utility pricing levels and/or enhance pricing time periods. 
     Methods are contemplated for operating HVAC systems in scenarios where utilities may enact enhanced pricing time periods of Critical Peak Pricing (CPP) on short notice, for example, one day in advance, in contrast with situations when utility pricing schedules may be planned and communicated well in advance, for example, for seasonal pricing. Users of HVAC systems, such as a homeowners, building superintendants, etc., that are aware of an impending CPP event may make manual inputs via the user interfaces of HVAC controllers to reduce energy consumption during the CPP event. 
     HVAC controllers such as controllers  300 ,  500 , and  600  of the present disclosure may be configured to accept entry of parameters for single-occurrence enhanced pricing time periods, similar to the configurations disclosed herein for accepting entry of parameters for recurring enhanced pricing time periods. CPP HVAC control parameters (such as start and end times of the CPP event, setpoints and/or setpoint offsets, and the like) may be entered, used for control of an HVAC system during a single CPP event, and then discarded (e.g., purged from controller memory). Alternately, one or more sets of parameters for potential CPP events may be entered into an HVAC controller and stored indefinitely, then activated by user input or other means when an actual CPP event is announced. 
     It is contemplated that there will be cases in which a utility declares a CPP event, but users that wish to reduce energy consumption during the event might not enter or activate CPP HVAC parameters. In such a case, the opportunity to reduce energy consumption during the CPP could be lost. However, the present disclosure provides methods and devices that allow control of an HVAC system by a local HVAC controller according to at least one CPP HVAC control parameter even without explicit intervention by a user. For example,  FIG. 21  is a flow diagram of an illustrative method  700  for operating a utility-powered HVAC system, such as system  10  of  FIG. 1 , which includes predicting a CPP event. 
     Method  700  includes at block  702  controlling an HVAC unit with a local HVAC controller according to at least one nominal HVAC control parameter, for example, as in the case of an HVAC system being controlled in accordance with a nominal schedule. At  704 , method  700  includes recording in a memory of the local HVAC controller at least one measure related to an environmental condition of the building. Such at least one measures may include, for example, an outdoor temperature, humidity, barometric pressure, and/or entropy, as might be recorded by one or more external sensors  40  of HVAC system  10  of  FIG. 1 . Another example of a measure related to an environmental condition of the building could be a measure of system load, for example, the cycle time of an air conditioning compressor, the amount of electrical energy consumed in a time interval, the slope of the inside temperature change versus time when the air conditioning compressor is active, the slope of the inside temperature change versus time when the air conditioning compressor is inactive, etc. In some illustrative embodiments, the measure or measures may be recorded twice or more during a time period, which may, for example, allow for a more accurate assessment of the environmental condition of the building. 
     Based at least in part upon the measure(s) related to an environmental condition of the building recorded at block  704 , at  706 , the method  700  may include predicting a CPP event of a utility supplying power to the building. Some possible non-limiting examples of how a prediction may be made including: a prediction of a next-day CPP event may be based on a dry-bulb temperature exceeding a threshold on the current day; a temperature trend over several days may indicate an increased likelihood of a CPP event on the current day; a morning rate of rise in outdoor air (specific) enthalpy may presage an afternoon CPP event. 
     As part of the prediction process, a first measurement of an environmental parameter (such as, for example, an outdoor air temperature) may be used to forecast a future value for the environmental parameter, providing a basis for making a CPP prediction. Historical data of environmental conditions preceding past CPP events may be analyzed to refine prediction rubrics. In general, the method may allow any suitable prediction logic to be used. An HVAC controller may be provided with software code to carry out the prediction in any appropriate way. Such code may be updated over the life of the controller, if desired. An installer and/or an HVAC system user may enter or adjust parameters to tune the predictions of CPP events made by the HVAC controller. Further, in some illustrative embodiments, predicting a CPP event may include determining a probability value of occurrence of the CPP event, and subsequent steps of method  700  may vary depending on the probability value determined. 
     If a CPP event is predicted at block  706 , method  700  may include at block  708  controlling the HVAC unit with the local HVAC controller according to at least one CPP HVAC control parameter. Controlling according to CPP HVAC control parameter(s) results in consuming less energy during the CPP event (when rates are elevated) relative to controlling according to nominal HVAC control parameter(s). Any suitable CPP HVAC control parameters that result in such reduced energy consumption may be used. CPP HVAC control parameters may be obtained in any appropriate way. CPP HVAC control parameters may be entered manually by a user before or after a prediction of a CPP event. CPP HVAC control parameters may be modified values of nominal HVAC control parameters, or they may not have nominal HVAC control parameter analogs. CPP HVAC control parameters may include start and end times for a CPP event enhanced pricing time period and an associated utility pricing level setpoint(s) and/or setpoint offset(s), as described herein. Such CPP HVAC control parameters may be used to override, overlay, or modify a nominal schedule to result in a utility pricing operating schedule. In some cases, CPP HVAC control parameters may include parameters related to executing HVAC system operation for pre-cooling inside air of the building in advance of the CPP event. In some illustrative embodiments, where a probability value of occurrence of the CPP event is determined in step  706 , a value of one or more CPP HVAC control parameters may be assigned depending at least partially on the determined probability value of occurrence. This is one way, for example, that the response to an uncertain occurrence of the CPP event may be modulated. The more certain it is predicted that a CPP event will occur, the more definite and/or severe the control response of the HVAC system may be. When the occurrence of a CPP event is less certain, a milder control response maybe considered appropriate. 
     If a CPP event is predicted, method  700  may be extended to communicate a CPP signal to a non-HVAC device. In such a case, the non-HVAC device may also reduce energy consumption during the CPP event time period. 
     Method  700  of  FIG. 21  may be extended to accepting a user selection of whether or not predictive CPP HVAC system control is desired. The step at block  708  of controlling the HVAC unit according to CPP HVAC control parameters would only be executed if a CPP event was predicted and user selection indicated that predictive CPP HVAC system control was desired. Furthermore, in some illustrative embodiments, CPP event overrides may be selected, in which case control of the HVAC unit may revert to control according to nominal HVAC control parameters (such as according to a nominal schedule). A user may manually select a CPP event override (for example, prioritizing comfort in a particular situation over energy cost savings), or it may be selected based upon a current measure related to an environmental condition of the building. For example, a CPP event may be predicted, but during the time period of the predicted CPP event, milder than anticipated weather conditions may prevail, in which case it may be likely that the utility does not execute a CPP event, and it is then not desired to control according to CPP HVAC system control parameters. 
     The disclosure should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the invention can be applicable will be readily apparent to those of skill in the art upon review of the instant specification.