Find Azure App Service Plans with no App Services associated with them.

Get-AzEmptyAppServicePlans.ps1

<#
.SYNOPSIS
    Find empty Azure App Service Plans
.DESCRIPTION
    Find Azure App Service Plans in the current Azure Context with no App Services associated with them.
    These empty App Service Plans will potentially be incurring unneccessary charges.
.EXAMPLE
    #Return a list of Empty App Service Plans in the current Azure Context
    Get-AzEmptyAppServicePlans
.EXAMPLE
    #Remove any empty App Service Plans in the current Azure Context
    Get-AzEmptyAppServicePlans | Remove-AzAppServicePlan
    #Append with -Force to bypass confirmation
.EXAMPLE
    #List the Name and Resource Group Name of any empty App Service Plans in the current Azure Context
    Get-AzEmptyAppServicePlans | Select-Object Name, ResourceGroup
#>
function Get-AzEmptyAppServicePlans{
    Return( Get-AzAppServicePlan | Where-Object {$_.NumberOfSites -eq 0})
}