First run
When you first open AirCompare, it will ask you for 3 authorizations. Just go ahead and accept those. Read the section "
About Notifications, Location Services and Homekit access” following at the bottom for an explanation of your options if you care to know more about those.

You should see a Main screen that looks like this. It will be cramped on an iPhone 5 screen but should look nice on any later device.

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Settings and Controls

In addition to the controls on the Main screen, AirCompare needs several customized settings. These are all accessible from the Main screen by clicking the “Settings” icon in the upper left corner and are described here in the order they appear.

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• HomeKit
If you have no HomeKit appliances, you may choose to disable any use of HomeKit by AirCompare. This will make the app a little snappier since it won’t be wasting time or wifi resources trying to find HomeKit devices that don’t exist. This applies to the individual fan/window/ventilation and thermostat devices as well.

If you have one or both HomeKit appliances, set them up using the software they came with or Apple’s Home app. Then in the AirCompare settings, select your “Home” and the name of your accessory, its service, and finally the characteristic of the service. For instance an accessory might be a switched outlet with a service you’ve named “Living Room Lamp”, with a characteristic “Power state” that you can turn on or off. If you have a HomeKit thermostat, AirCompare needs the characteristic that corresponds to the “Target Temperature”.

• Units
In this section, choose the units you prefer for temperature, pressure and so on. You might choose to accept the defaults that (I think) will already be there (on the left-hand side).

• Web Sources
Choose here the website you prefer for weather. Note that Open Weather does not provide a precipitation probability. If you choose Open Weather, you will not receive any warnings to close your windows as rain approaches. The choice of electricity supplier only matters if you have variable rate pricing from one of the two suppliers listed.

• Times
AirCompare allows you to choose a daily time to turn down the thermostat, typically around bedtime, and the degrees to cool down (in the next “Sliders” section). You also select the time to turn the temperature back to normal.

Most alerts from AirCompare show the latest background updates to the weather and electric rate. The frequency of these alerts shows you how often iOS is allowing AirCompare to fetch fresh data. They may arrive every few minutes or hours apart. These alerts are silent unless user action is suggested, for instance to open or close the windows or to adjust the thermostat. You can choose when to silence ALL alerts so you are not bothered by them at night, and when to let them begin again in the morning. Note that in Night Mode, the app is actively responding to updates in the foreground and no alerts are sent.

• Sliders
Select the degrees to cool down at night, to change when you are away (typically up in the summer and down in the winter), and the risk of rain that will trigger a warning to close your windows.

• Location
A manually entered location overrides the users ‘Home’ location set in the geofence.
Setting the geofence tells AirCompare where your home is so that it knows the location to fetch weather for, and can monitor if you are home or not.

(This view has since changed slightly to simplify setting your geofence.)

The “Ventilation” screen

AirCompare contains a full psychrometric calculator that can be accessed directly on this screen. This also allows manual entry of your indoor conditions (temperature and %RH) if you do not have a HomeKit thermostat to supply these data.


The “Thermostat” screen

AirCompare lets you adjust your thermostat in response to changing electricity prices. If your electrical rate is fixed, this feature is not relevant.

If your rate is variable and your heating is not electrical, reducing the temperature in the winter will only reduce the use of your furnace fan for a modest savings.

Larger savings come in the summer when your air conditioner is using electricity. Electrical rates can climb very high on peak usage days and you can save money by accepting a warmer temperature until rates fall again. Occasionally rates at night or early morning may even become negative, and that’s a great time to chill your home down as much as you can tolerate. Your electricity supplier will pay you to run your A/C! AirCompare in Night Mode can keep a constant vigil for such an opportunity.

Here’s an example of my electricity rates from July 2 of last year. Notice how the price (red line) dropped slightly below 0 for the 5AM hour and rose to nearly 10¢ at 5PM.

Here’s a demonstration of AirCompare controlling my Ecobee thermostat during the night of July 20th last year. You can see that it dropped the setting (blue line) for an hour starting about 1AM. This was in response to a low electricity rate of ~1¢/kWh during that hour.


About Notifications, Location Services and Homekit access

When you first open AirCompare, it will ask for your authorization for these three items. Here is an explanation of your options. Note that you can change your choices at any time in your iPhones Settings:

Settings>Notifications>AirCompare (suggested setting: all switches “On”)
Settings>Privacy>Location Services>AirCompare (suggested setting: Always)
Settings>Privacy>HomeKit (suggested setting: “On”)

Why does AirCompare need access to these services?
The primary function of AirCompare is to give you advice on how to operate your HVAC system most efficiently as environmental conditions change, and to make the appropriate changes automatically in homes with HomeKit-enabled HVAC components.

AirCompare is designed to perform its chores in the background, requiring only occasional attention from the user once your preferences have been set.

However, from the background, there is no way for AirCompare to keep you informed of current conditions or to make changes to HomeKit devices without the requested authorizations.
The more often you use AirCompare, the more often iOS will allow it to check for fresh internet data.

You can use AirCompare without notifications. It will continue to monitor current conditions while in the background and will calculate the best settings for your HVAC system. You just won’t know what those settings are without manually bringing the app to the foreground. The purpose of the notifications is to alert you when AirCompare, in the background, has detected a change that warrants adjusting your HVAC.

Note also that Apple does not allow any app to control HomeKit devices from the background. So in response to a notification, AirCompare must be brought to the foreground by the user to either read the advice on ideal HVAC settings or to allow AirCompare to make those changes automatically via HomeKit.

AirCompare silences notifications at night, for the time interval you choose.
You can also use the options in Settings as above to silence all notifications regardless of time-of-day.

Location Services
You can use AirCompare without Location Services. Most people want to use less energy when they’re not home, for instance by setting the thermostat to a higher target temperature in the summer, or lower in the winter, if no one is home. AirCompare allows you to choose a change in temperature to apply when it detects that you have left your home geofence. It obviously cannot make this change if it's unaware of the user’s location. This opportunity for significant energy savings will be unavailable and AirCompare will assume you are always ‘home’.