This script allows to upscale/downscale an Azure Virtual Machine. Credits to Wojciech Lepczyński (https://lepczynski.it/en/azure_en/automatic-azure-vm-resizing/). Changes: update from AzureRM to Az.

UpscaleDownscale-VM.ps1

[CmdletBinding()]
param(
	[Parameter(Mandatory=$True)]
	[String] $VMName = "VMName",

	[Parameter(Mandatory=$True)]
	[String] $ResourceGroupName = "ResourceGroupName",
	
	[Parameter(Mandatory=$True)]
	[String] $Size = "VMSize"
)

# Keep track of time
$StartDate=(GET-DATE)

$connectionName = "AzureRunAsConnection"

try
{
	# Get the connection "AzureRunAsConnection"
	$servicePrincipalConnection=Get-AutomationConnection -Name $connectionName         
	"Logging in to Azure..."
	Add-AzAccount `
	-ServicePrincipal `
	-Tenant $servicePrincipalConnection.TenantId `
	-ApplicationId $servicePrincipalConnection.ApplicationId `
	-CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint 
}
catch {
	if (!$servicePrincipalConnection)
	{
		$ErrorMessage = "Connection $connectionName not found."
		throw $ErrorMessage
	} 
	else
	{
		Write-Error -Message $_.Exception.Message
		throw $_.Exception
	}
}

try{
	$VirtualMachine = Get-AzVM -Name $VMName -ResourceGroupName $ResourceGroupName -Status
	if (!$VirtualMachine)
	{
		Write-Error "$($VMName) not found in $($ResourceGroupName)"
		return
	}

	$VMStats = $VirtualMachine.Statuses
	$VMStats= ($VMStats | Where Code -Like 'PowerState/*')[0].DisplayStatus

	# if VM is running, execute the script
	if ($VMStats -eq "VM running")
	{
		$vm = Get-AzVM -ResourceGroupName $ResourceGroupName -Name $VMname -Status
		$vm = $vm.Statuses.DisplayStatus | Select-String -Pattern "VM running"

		# if the machine you want to resize has "running" state, run the script
		if($vm -match "VM running")
		{
			$vm1 = Get-AzVM -ResourceGroupName $ResourceGroupName -Name $VMname
			$oldVMSize = $vm1.HardwareProfile.VmSize
			$vm1.HardwareProfile.VmSize = $Size
			Update-AzVM -VM $vm1 -ResourceGroupName $ResourceGroupName
			Write-Output "Changed $($VMName) vm size from $($oldVMSize) to $($Size)"
		}
		else{
			Write-Error "Cannot upscale/downscale VM $($VMName) while the status is $($vm)"
		}
	}else{
		Write-Error "Cannot upscale/downscale VM $($VMName) while the status is $($VMStats)"
	}
	# Show when finished
	$Duration = NEW-TIMESPAN –Start $StartDate –End (GET-DATE)
	Write-Output "Done in $([int]$Duration.TotalMinutes) minute(s) and $([int]$Duration.Seconds) second(s)"
}
catch{
	Write-Error -Message $_.Exception.Message
	throw $_.Exception
}