# Patent

## Title
Temperature controller with model-based time to target calculation and display

## Abstract

A thermostat is described for controlling air temperature in a building. The time associated with causing the controlled air temperature to reach a target temperature is estimated and displayed to a user. Input from a user indicating the target temperature can be received and the estimating and displaying can be carried out in real time. The thermostat can be wall-mounted or the user input can be received and estimated time can be displayed using a remote device, for example that communicates wirelessly with other components of the HVAC system.

## Background
COPYRIGHT AUTHORIZATION
A portion of the disclosure of this patent document may contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
BACKGROUND
Building heating ventilation and air-conditioning (HVAC) systems account for a significant percentage of total energy consumption. Thus, a significant savings in HVAC energy usage can have an impact on total energy consumption. Programmable thermostats have been commercially available for many years and are used in many residential and light industrial settings. However, the typical user in the residential and light-industrial setting is relatively unsophisticated in terms of HVAC technology and efficiency. Despite the fact that HVAC energy use makes up a significant portion of total energy use in a residential or light industrial setting, a typical residential or light industrial occupant using a thermostat to manually input a set point or target temperature —either to increase the current temperature in the case of heating, or decrease the current temperature in the case of cooling —does not have a good understanding of how much energy is required to carry out the increase or decrease in temperature being called for. For example, a typical user does not have a good idea of how much energy it takes to raise the temperature of his or her dwelling by various amounts on a cold winter day. Some sophisticated thermostats are capable of calculating and displaying cost information associated with set point changes. For example, see U.S. Pat. No. 7,392,661, which discusses an HVAC system controller which estimates the energy cost or savings incurred due to a user-instigated change in a climate control schedule. Estimated costs or savings can be displayed to the user in an effort to give the user a basis for making decisions. However, it is believed that displaying costs and/or savings alone does not necessarily give many users a good awareness of HVAC system usage.
SUMMARY
According to some embodiments a method is provided for controlling air temperature in a building, such as with an HVAC system. The method includes estimating an amount of time associated with the controlled air temperature reaching a target temperature; and displaying information to a user representative of the estimated amount of time. According to some embodiments, input from a user indicating the set point or target temperature can be received, and the estimating and displaying can be carried out in real time. The method can also include receiving further targets from a user and re-estimating and displaying an updated time to reach the target temperature. The method can be carried out using a wall-mounted thermostat or using a remote unit via wireless communication.
According to some embodiments, the displayed information includes a numeric representation of the estimated amount of time to reach the target temperature. The information includes can also a graphical representation of the estimated amount of time. The method can be used with an HVAC system that includes single-stage and/or multi-stage heating and/or cooling functionality.
According to some embodiments, the method can include estimating an amount of energy and/or cost associated with causing the controlled air temperature to reach the target temperature; and displaying energy information and/or cost to a user representative of the estimated amount of energy.
According to some embodiments, a system is provided for controlling air temperature in a building. The system includes a processing system adapted and programmed to estimate an amount of time associated with causing the controlled air temperature to reach a target temperature; and a display adapted to display to a user information representative of the estimated amount of time. According to some embodiments, the system is a circular thermostat which can have a rotating outer member adapted to receive input from a user indicating the target temperature.
According to some embodiments a system for controlling temperatures other than air temperature are provided, such a controlling system forming part of a hot water heating system.
As used herein the term “residential” when referring to an HVAC system means a type of HVAC system that is suitable to heat, cool and/or otherwise condition the interior of a building that is primarily used as a single family dwelling An example of a cooling system that would be considered residential would have a cooling capacity of less than about 5 tons of refrigeration (1 ton of refrigeration=12,000 Btu/h).
As used herein the term “light commercial” when referring to an HVAC system means a type of HVAC system that is suitable to heat, cool and/or otherwise condition the interior of a building that is primarily used for commercial purposes, but is of a size and construction that a residential HVAC system is considered suitable. An example of a cooling system that would be considered residential would have a cooling capacity of less than about 5 tons of refrigeration.
As used herein the term “target temperature” refers to a temperature, such as a set point temperature toward which a structure or enclosure being conditioned by an HVAC system is moving. The change in temperature toward a target temperature may be under active heating or cooling by the HVAC system and/or it may be due to passive effects such as drifting due to influence of conditions external to the enclosure or structure being conditioned.
It will be appreciated that these systems and methods are novel, as are applications thereof and many of the components, systems, methods and algorithms employed and included therein. It should be appreciated that embodiments of the presently described inventive body of work can be implemented in numerous ways, including as processes, apparata, systems, devices, methods, computer readable media, computational algorithms, embedded or distributed software and/or as a combination thereof. Several illustrative embodiments are described below.



BRIEF DESCRIPTION OF THE DRAWINGS
The inventive body of work will be readily understood by referring to the following detailed description in conjunction with the accompanying drawings, in which:
FIG. 1 is a diagram of an enclosure for which thermodynamic behavior is predicted, according to some embodiments;
FIG. 2 is a diagram of an HVAC system, according to some embodiments;
FIGS. 3A, 3B and 3C illustrate a thermostat for controlling temperature in an enclosure, according to some embodiments;
FIG. 4 shows a thermostat adapted to display time to reach a target temperature, according to some other embodiments;
FIGS. 5A, 5B and 5C show a thermostat adapted to display time to reach a target temperature, according to some other embodiments;
FIG. 6 illustrates a thermostat displaying time to reach target temperature information, according to some other embodiments;
FIG. 7 illustrates a water heater control unit capable of displaying time to reach target temperature, according to some embodiments;
FIG. 8 illustrates a thermostat capable of displaying time as well as other values associated with reaching a target temperature, according to some embodiments;
FIG. 9 is a flow chart showing steps in real time display of estimated time to reach a target, temperature according to some embodiments;
FIG. 10 is a block diagram illustrating the calculation of a time to reach a target temperature, according to some embodiments;
FIG. 11 illustrates a thermostat capable of displaying times to reach target temperature based on various factors, according to some embodiments; and
FIGS. 12A-B illustrate a thermostat capable of displaying time to reach a target temperature without active HVAC system control, according to some embodiments



DETAILED DESCRIPTION
A detailed description of the inventive body of work is provided below. While several embodiments are described, it should be understood that the inventive body of work is not limited to any one embodiment, but instead encompasses numerous alternatives, modifications, and equivalents. In addition, while numerous specific details are set forth in the following description in order to provide a thorough understanding of the inventive body of work, some embodiments can be practiced without some or all of these details. Moreover, for the purpose of clarity, certain technical material that is known in the related art has not been described in detail in order to avoid unnecessarily obscuring the inventive body of work.
FIG. 1 is a diagram of an enclosure in which temperature is controlled, according to some embodiments. Enclosure 100, in this example is a single-family dwelling. According to other embodiments, the enclosure can be, for example, a duplex, an apartment within an apartment building, a light commercial structure such as an office or retail store, or a structure or enclosure that is a combination of the above. Thermostat 110 controls HVAC system 120 as will be described in further detail below. According to some embodiments, the HVAC system 120 has a cooling capacity less than about 5 tons. According to some embodiments, temperature is controlled by other systems such as hot water heater 130. According to some embodiments, a remote device 112 wirelessly communicates with the thermostat 110 and can be used to display information to a user and to receive user input from the remote location of the device 112. According to some embodiments, the device 112 can be located outside of the enclosure 100.
FIG. 2 is a diagram of an HVAC system, according to some embodiments. HVAC system 120 provides heating, cooling, ventilation, and/or air handling for the enclosure, such as a single-family home 100 depicted in FIG. 1. The system 120 depicts a forced air type heating system, although according to other embodiments, other types of systems could be used such as hydronic, in-floor radiant heating, heat pump, etc. In heating, heating coils or elements 242 within air handler 240 provide a source of heat using electricity or gas via line 236. Cool air is drawn from the enclosure via return air duct 246 through fan 238 and is heated heating coils or elements 242. The heated air flows back into the enclosure at one or more locations via supply air duct system 252 and supply air grills such as grill 250. In cooling an outside compressor 230 passes gas such as freon through a set of heat exchanger coils to cool the gas. The gas then goes to the cooling coils 234 in the air handlers 240 where it expands, cools and cools the air being circulated through the enclosure via fan 238. According to some embodiments a humidifier 254 is also provided. Although not shown in FIG. 2, according to some embodiments the HVAC system has other known functionality such as venting air to and from the outside, and one or more dampers to control airflow within the duct systems. The system is controlled by algorithms implemented via control electronics 212 that communicate with a thermostat 110.
Thermostat 110 controls the HVAC system 120 through a number of control circuits. Thermostat 110 also includes a processing system 260 such as a microprocessor that is adapted and programmed to controlling the HVAC system and to carry out the techniques described in detail herein.
FIGS. 3A, 3B and 3C illustrate a thermostat for controlling temperature in an enclosure, according to some embodiments. Thermostat 310 includes control circuitry and is electrically connected to an HVAC system, such as thermostat 110 in FIGS. 1 and 2. Thermostat 310 is wall mounted, is circular in shape and has an outer rotatable ring 312 for receiving user input. Thermostat 310 has a large frontal display area 314. According to some embodiments, thermostat 310 is approximately 80 mm in diameter. The outer ring 312 allows the user to make adjustments, such as selecting a new target temperature. For example by rotating the outer ring 312 clockwise, the target temperature can be increased, and by rotating the outer ring 314 counter-clockwise, the target temperature can be decreased. According to some embodiments, the large central numbers 320 can be used to display the current temperature to users, as is shown in FIG. 3A. According to some embodiments a portion 316 of the display area 314 can be used to display a color that is associated with the current HVAC function. For example, if the HVAC system is currently heating the enclosure, the area 316 can be shown in red. If the HVAC system is currently cooling the enclosure, the area 316 can be shown in blue. If the HVAC system is neither heating or cooling, the area 316 can be shown in a neutral color, or a color such a black which is used as the background color for the display area 314.
According to some embodiments, the thermostat 310 displays the estimated time to reach the current target temperature. In the example shown, the time to reach the target temperature is displayed to the user in two ways. Numbers 322 display the numerical time in hours, minutes and seconds which is estimated to be needed to reach the target temperature. Additionally, or alternatively according to some embodiments, a graphical display 324 is used to indicate the amount of time to reach the target temperature. Thus as time elapses and the temperature in the enclosure gets closer to the target temperature, the numerical display 322 and the graphical display 324 change to reflect shorter times.
In FIG. 3B, the central numbers 320 display the target temperature, which in this case is 75 degrees. The smaller words 326 are used to indicate to the user that the central numbers represent the target temperature, instead of the current temperature, as well as indicate the HVAC function (e.g. heating or cooling) that is currently active. According to some embodiments, when the current temperature and the target temperature differ by more than a predetermined amount, for example 2 degrees, the central numbers 320 alternate between the current temperature as shown in FIG. 3A and the target temperature as shown in FIG. 3B.
According to some embodiments, other graphical means, such as slowly oscillating the size of the numbers 320 can also be used to indicate that the HVAC system in the process of moving the enclosure temperature towards a target temperature. According to some embodiments, the target temperature is displayed as in FIG. 3B whenever the target temperature is being altered, such as when a user is making adjustments to the target, such as by rotating the outer ring 312 or by remote control, or when the target is automatically being adjusted according, for example, to a predetermined program. According to some embodiments, thermostat 310 is a remote unit, such as a portable table-top thermostat controller and display unit, which is adapted to communicate wirelessly with a thermostat or component of an HVAC control system. According to some embodiments the target temperature is provided remotely by a user, for example, using a smart phone or remote internet connection from a location outside the enclosure, and the estimated time to reach the new target is displayed to the user on the remote device.
According to some embodiments, a maximum time can be displayed, such as 24 hours, if the estimated time to reach the target temperature is greater than that amount, or if it is estimated that the HVAC system is unable to obtain the target temperature given its capacity and/or other conditions (e.g. such as outdoor temperature). FIG. 3C illustrates an example of such a display mode. In this example, the target temperature has been set to a high temperature as indicated by central number display 320. The graphical display 324 is showing a maximum time. Numerical display 322 is showing a maximum time, in this case 24 hours. According to some embodiments, the numerical display 322 and/or the graphical display 324 can blink so as to indicate a warning or error to the user.
FIG. 4 shows a thermostat adapted to display time to reach a target temperature according to some other embodiments. Thermostat 410 is similar to thermostat 310 as shown in FIGS. 3A, 3B and 3C with a large display area, rotatable outer ring 412, large central numbers 420 and numerical time to reach a target temperature display 422. However, the graphical display 424 is slightly different in that it shows a solid curved bar that fills up an annular section 426 instead of a group of radial bars such as shown in FIGS. 3A, 3B and 3C.
FIGS. 5A, 5B and 5C show a thermostat adapted to display time to reach a target temperature, according to some other embodiments. Thermostat 510 includes control circuitry and is electrically connected to an HVAC system, such as thermostat 110 in FIGS. 1 and 2. Thermostat 510 is circular in shape and has an outer rotatable ring 512 for receiving user input. Thermostat 510 has a large frontal display area 514. According to some embodiments, thermostat 510 is approximately 80 mm in diameter. The outer ring 512 allows the user to make adjustments, such as selecting a new target temperature, as is described with respect to FIGS. 3A-3C.
According to some embodiments, other graphical means, such as slowly oscillating the size of the numbers 320 can also be used to indicate that the HVAC system in the process of moving the enclosure temperature towards a target temperature. According to some embodiments, the target temperature is displayed as in FIG. 3B whenever the target temperature is being altered, such as According to some embodiments, the large numbers 520 can be used to display the current temperature to users, as is shown in FIG. 5A. According to some embodiments, the thermostat 510 displays the estimated time to reach the current target temperature. In addition to the numerical display 522, according to some embodiments, a graphical display in the form of a needle 524 is used to indicate the amount of time to reach the target temperature. Label 526 informs the user that the needle position represents the estimated time to reach the target temperature. Thus, as time elapses and the temperature in the enclosure gets closer to the target temperature, the numerical display 522 and the graphical display 524 change to reflect shorter times.
In FIG. 5B, the central numbers 520 display the target temperature, which in this case is 76 degrees. The smaller words 528 are used to indicate to the user that the central numbers represent the target temperature, instead of the current temperature, as well as to indicate the HVAC function (e.g. heating or cooling) that is currently active. In FIG. 5C, illustrates an example of when the HVAC cooling system is active, according to some embodiments. In the example shown, the central numbers 520 display the target temperature, which in this case is 72 degrees. The smaller words 528 are used to indicate to the user that the central numbers represent the target temperature, instead of the current temperature, as well as to indicate that the HVAC cooling function is currently active.
FIG. 6 illustrates a thermostat displaying time to reach target temperature information, according to some other embodiments. Thermostat 610 is a rectangular wall mounted thermostat having a large graphical display area 614. The user can manually input changes in target temperature using buttons 611 and 612. The display area 614 includes a graphical plot curve 624 that represents the time estimated to reach the target temperature. The vertical axis represents temperature and shows the current temperature 620 and the target temperature 626. The horizontal axis represents time, and displays the estimated time 622 to reach the target temperature.
According to some embodiments, a controller for controlling temperature in applications other than HVAC are provided. For example, FIG. 7 illustrates a water heater control unit capable of displaying the time to reach a target temperature, according to some embodiments. Water temperature controller 710 has a large graphical display area 714. The user can manually input changes to the target temperature using buttons 711 and 712. The display area 714 includes the current water temperature 720, the target temperature 722 and the estimated time 724 to reach the target temperature.
Providing a thermostat that displays the estimated time to reach a target temperature advantageously conveys to the user an impact of the target temperature decision on energy use as well as an increased awareness of HVAC system usage. When a user makes a decision to manually input a new target temperature, the user receives important feedback as to how hard the HVAC system needs to work to obtain that temperature. It has been found that time is a very good parameter to display to a user in order to convey to an average non-technical user the relative effort or difficulty for the HVAC system to obtain a given target temperature. As described more fully below, according to some embodiments, the display of the estimated time to reach the new target temperature is made in real time, so that the user can nearly immediately see the impact of the user's decisions. It has been found that in this way, the user is advantageously trained or educated so as to become more intuitively familiar with the HVAC system, which in turn leads to more economical and environmentally friendly use of energy. It has been found that many HVAC users falsely believe that setting a higher target temperature will make the space warm up faster in the case of heating, and/or believe that setting a lower target temperature will make the space cool down faster in the case of cooling. Displaying the time to reach the target temperature thus educates that user that this is usually not the case. Although displaying the time to the target temperature may not directly save energy, it gives the user a better understanding about HVAC usage and may therefore allow for greater savings in the long run. According to other embodiments, other parameters than time can be displayed to a user to provide useful feedback to the user.
FIG. 8 illustrates a thermostat capable of displaying time as well as other values associated with reaching a target temperature, according to some embodiments. Thermostat 810 is a circular wall mounted thermostat having a large graphical display 814 adapted to display information to a user, and a rotatable outer ring 812 adapted to receive user input. As in the case of other embodiments described above, the display area 814 includes a numerical display 820 of the target temperature and/or the current temperature. The time estimated to reach the target temperature is displayed both graphically by bars 824 and numerically by the hours, minutes and seconds display 822. Additionally, other information is displayed to the user relating to reaching the target temperature, including estimated Therms 828 to reach the target temperature, and the estimated cost 826 to reach the target temperature. According to some embodiments, other units of energy such as Calories and/or joules are displayed instead of, or in addition to Therms display 828.
FIG. 11 illustrates a thermostat capable of displaying times to reach target temperature based on various factors, according to some embodiments. Thermostat 1110 is a circular wall mounted thermostat having a large graphical display 1114 adapted to display information to a user, and a rotatable outer ring 1112 adapted to receive user input. As in the case of other embodiments described above, the display area 1114 includes a numerical display 1120 of the target temperature and/or the current temperature. Multiple times are calculated and displayed to the user based on the use of resources. For example, display 1122 shows the time to the target temperature when using a single stage, and display 1124 shows the time to the target temperature when using two stages in a building having a multi-stage equipped HVAC system. Additionally, according to some embodiments a display 1126 displays the time to reach the target temperature by using passive resources, such as opening a window. By displaying information such as shown in FIG. 11, the user can be educated as to the behavior of the conditioned enclosure under the influence of various passive and active conditioning systems.
FIGS. 12A-B illustrate a thermostat capable of displaying time to reach a target temperature without active HVAC system control, according to some embodiments. Thermostat 1210 is a circular wall mounted thermostat having a large graphical display 1214 adapted to display information to a user, and a rotatable outer ring 1212 adapted to receive user input. As in the case of other embodiments described above, the display area 1214 includes a numerical display 1220 of the target temperature and/or the current temperature 1221. The time estimated to reach the target temperature is displayed both graphically by bars 1224 and numerically by the hours, minutes and seconds display 1222. In the case of FIG. 12A, the time to reach the target temperature 1220 is calculated and displayed as drifting, that is, without active HVAC input. For example the display as shown in FIG. 12A could be used when the target temperature is being lowered during the nighttime or an expected un-occupied time. In the case of FIG. 12B the target temperature is a resting temperature which is calculated as the temperature the conditioned area would come to rest at without any active HVAC system input. By displaying information such as illustrated in FIGS. 12A and 12B, the user can be further educated as to the behavior of the conditioned enclosure.
FIG. 9 is a flow chart showing steps in real time display of estimated time to reach a target temperature, according to some embodiments. In step 910 the user inputs a new target temperature, for example by rotating the outer ring in the example of the thermostats of FIGS. 3A-C. In step 912, the thermostat's processing system calculates a time estimated to reach the target temperature. In step 914 the estimated time is displayed to the user. The steps 912 and 914 are preferably performed quickly, such as a few hundreds of milliseconds or less, such that the user perceives a nearly instantaneous response to the new target temperature input. In step 916, the user views the displayed estimated time and decides in step 918 if the new target should be kept in light of the estimated time to reach the new target temperature. If the estimated time is not reasonable, the user sets a new target. If the estimated time is reasonable, in step 920, the target temperature is kept and the HVAC system heats or cools the enclosure to the new target temperature. It has been found that if the calculation and display is performed in real time, a beneficial education of the user as to the workings, efficiencies and limitations of the HVAC system is provided.
According to some embodiments, the HVAC system being controlled by the thermostat as described herein includes a multi-stage heating and/or multistage cooling system. It has been found that real time calculation and display as described in the flow chart of FIG. 9 is especially useful to educating users in the case where multi-stage heating and/or cooling is used. In the case of multi-stage heating or cooling, providing real-time feedback to the user of manual target temperature changes informs the user as to how large of a change is required in order for a second stage to be activated.
According to some embodiments the HVAC system being controlled is one in which the user is likely to be relatively unsophisticated in terms of HVAC technology and operation. In such cases the education of user as described is highly beneficial. Thus, according to some embodiments, the use of the techniques described herein are preferably used in residential and/or light commercial HVAC installations. Such systems commonly have a maximum cooling capacity of about 5 tons.
FIG. 10 is a block diagram illustrating the calculation of a time to reach a target temperature, according to some embodiments. A model of thermodynamic characteristics of the enclosure is preferably used. For further details of such models, please refer to co-pending U.S. patent application Ser. No. 12/881,463 entitled “Thermodynamic Modeling for Enclosures,” filed on Sep. 14, 2010 (hereinafter “the '463 Application”) which is incorporated herein by reference. According to some embodiments, a system identification algorithm 1010 is used as described in the '463 Application.
According to some embodiments, system identification algorithm in 1010 is a mathematical model that can learn the dependence of time to temperature on several thermal and climate factors. According to some embodiments, the inputs 1020 can include both current indoor temperature and a window of temperature measurements immediately prior to the calculation. Other inputs can be an indicator of whether a single stage or several stages of cooling or heating are activated at the time. The algorithm may also take the length of each of the cooling or heating time elapsed. Other environmental factors such as outdoor temperature, indoor and/or outdoor humidity can also be inputs to the algorithm. The output 1030 of the algorithm is the estimated time to reach the target temperature. In some embodiments, the output may also contain an optional statistical confidence value representing our belief in the estimate.
The algorithm may learn the dependence of the outputs on the inputs using statistical methods and machine learning algorithms. For example, the computation may be done using a weighted mean of past observations, linear or non-linear regression, recursive filtering including Kalman filtering or other online or batch system identification methods for dynamical systems.
According to some embodiments, the computation is carried out continuously to account for continually changing inputs. The display of the time to temperature is updated continually to reflect the current estimate from the algorithm.
According to some embodiments, other types of algorithms are used to calculate the time to reach a target temperature. For example other techniques can be used to calculate certain intermediate values, such as house rest temperature, which can be used along with current temperature and outdoor temperature to calculate the time to target. According to some embodiments, a look up table is used in the algorithm 1010.
According to some embodiments the computation system that carries out the algorithm may reside at a location external to the thermostat, such as a computer located within the structure being conditioned or a computer or processing system located at a remote location. According to such embodiments, the computer or processing system making the computation may communicate with the thermostat to gather the inputs and communicate back the output for display.
According to some embodiments, the computation and display is made to the user during the time in which an observer sees the display. According to some embodiments, the computation and display is made in less than about 1 second.
According to some embodiments, the computation and display is made in less than about 0.5 seconds.
Although the foregoing has been described in some detail for purposes of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles thereof. It should be noted that there are many alternative ways of implementing both the processes and apparatuses described herein. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the inventive body of work is not to be limited to the details given herein, which may be modified within the scope and equivalents of the appended claims.

## Claims

1. A method for controlling air temperature in a building using an HVAC system including a wall-mounted thermostat, the method comprising:
operating the HVAC system to bring the controlled air temperature to a target temperature;
using a processing system within the wall-mounted thermostat to estimate an amount of time associated with the controlled air temperature reaching the target temperature based on a mathematical model of the thermodynamic characteristics of the building which learns a dependence of time to reach a target temperature using at least a current indoor temperature, wherein
computation of the estimated amount of time is performed by the processing system using past observations of times to reach target temperatures; and

displaying information on the wall-mounted thermostat to a user representative of the estimated amount of time, the information comprising:
a numeric representation of the estimated amount of time to reach the target temperature; and
a graphical representation of the estimated amount of time to reach the target temperature, the graphical representation comprising an arc of a circle that partially encircles a numeric representation of the target temperature.

2. A method according to claim 1 further comprising receiving input from a user indicating the target temperature.

3. A method according to claim 2 wherein the estimating and displaying are carried out in real time with respect to the user.

4. A method according to claim 3 wherein the estimating and displaying are carried out in less than about 0.5 seconds.

5. A method according to claim 3 wherein the estimating and displaying are carried out while the user views the displayed information.

6. A method according to claim 2 further comprising:
receiving a second input from a user indicating a second target temperature;
estimating a second amount of time associated with the controlled air temperature reaching the second target temperature; and
displaying second information to a user representative of the second amount of time.

7. A method according to claim 2 wherein the input is received from a user using the wall-mounted thermostat adapted to control the air temperature using the HVAC system.

8. A method according to claim 2 wherein the input is received from a user via wireless communication.

9. A method according to claim 1 wherein the HVAC system includes multi-stage heating and/or cooling functionality.

10. A method according to claim 9 wherein the displayed information includes estimated time using one stage and estimated time using more than one stage.

11. A method according to claim 1 wherein the HVAC system includes cooling functionality having a cooling capacity of less than about 5 tons.

12. A method according to claim 1 wherein the building is primarily a residential or light-industrial building.

13. A method according to claim 1 further comprising:
estimating an amount of energy associated with causing the controlled air temperature to reach the target temperature; and
displaying energy information to a user representative of the estimated amount of energy.

14. A method according to claim 13 wherein the energy information includes a value expressed in one or more units selected from a group consisting of:
Therms, Calories, and joules.

15. A method according to claim 1 further comprising:
estimating a cost associated with causing the controlled air temperature to reach the target temperature; and
displaying cost information to a user representative of the estimated cost.

16. A method according to claim 1 wherein the estimated time associated with the controlled air temperature reaching the target temperature is primarily under passive influences.

17. A method according to claim 16 wherein the passive influences include opening a window.

18. A method according to claim 16 wherein the target temperature is a natural rest temperature of the controlled air temperature in the building without the use of active control.

19. A system for controlling air temperature in a building comprising:
a processing system that controls an HVAC system to bring the controlled air temperature to a target temperature and the processing system is adapted and programmed to estimate an amount of time associated with the controlled air temperature reaching the target temperature based on a mathematical model of the thermodynamic characteristics of the building which learns a dependence of time to reach a target temperature using at least a current indoor temperature, wherein computation of the estimated amount of time is performed by the processing system using past observations of times to reach target temperatures; and
a display adapted to display to a user information representative of the estimated amount of time, wherein;
the processing system and the display are part of a wall-mounted thermostat, and
the information representative of the estimated amount of time comprises:
a numeric representation of the estimated amount of time to reach the target temperature; and
a graphical representation of the estimated amount of time to reach the target temperature, the graphical representation comprising an arc of a circle that partially encircles a numeric representation of the target temperature.

20. A system according to claim 19 wherein the wall-mounted thermostat is circular.

21. A system according to claim 20 further comprising a rotating outer member adapted to receive input from a user indicating the target temperature.

22. A system according to claim 19 wherein the wall-mounted thermostat communicates with other portions of the HVAC system via conductive wires.

23. A system according to claim 19 wherein the system wirelessly communicates with one or more components of an HVAC system that controls the air temperature in the building.

24. A system for controlling temperature in a building, comprising:
a processor that controls an HVAC system to bring the controlled air temperature to a target temperature and the processor is adapted and programmed to estimate an amount of time for a temperature at a current temperature to reach the target temperature based on a mathematical model of the thermodynamic characteristics of the building which learns a dependence of time to reach the target temperature using a current indoor temperature, wherein computation of the estimated amount of time is performed by the processor using past observations of times to reach target temperatures; and
a display adapted to display the estimated amount of time to a user, wherein the processor and the display are part of a wall-mounted thermostat and the estimated time is displayed to the user in the form of:
a numeric representation of the estimated amount of time to reach the target temperature; and
a graphical representation of the estimated amount of time to reach the target temperature, the graphical representation comprising an arc of a circle that at least partially encircles a numeric representation of the target temperature.

25. A system according to claim 24 wherein the temperature is water temperature and the system forms part of a hot water heating system.

26. A system according to claim 24 wherein the estimate is continuously updated.

27. A system according to claim 24 wherein the mathematical model includes statistical methods and machine learning algorithms.

28. A system according to claim 24 wherein the processor is further adapted and programmed to calculate a statistical confidence value representing confidence in the estimate of the amount of time for the temperature at the current temperature to reach the target temperature.

29. A method according to claim 1, further comprising:
repeatedly updating, by the wall-mounted thermostat, the displayed information on the wall-mounted thermostat to reflect an updated estimate of the amount of time to reach the target temperature based on recomputation of the mathematical model.

30. A system for controlling air temperature in a building according to claim 19 wherein the processing system is further configured to repeatedly update the displayed information on the wall-mounted thermostat to reflect an updated estimate of the amount of time to reach the target temperature based on recomputation of the mathematical model.

31. A system for controlling temperature in a building according to claim 24, wherein the processor is further configured to repeatedly update the displayed information on the wall-mounted thermostat to reflect an updated estimate of the amount of time to reach the target temperature based on recomputation of the mathematical model.