Measure power usage on Windows on Arm with PowerShell

Sample the battery status

Querying battery status provides a way to measure power usage without an external power meter. Battery monitoring is also convenient because data collection and logging can be automated.

A PowerShell script launches the video decoding task, samples battery status, and outputs the collected data to a CSV formatted file.

Open your code editor, copy the content below, and save it as sample_power.ps1:

    

        
        
param (
    [string]$exePath = "ffmpeg-n7.1.1-56-gc2184b65d2-win64-gpl-7.1\ffmpeg-n7.1.1-56-gc2184b65d2-win64-gpl-7.1\bin\ffplay.exe",
    [string[]]$argList = @("-loop", "15", "-autoexit", "RaceNight_1080p.mp4"),
    [int]$interval = 10,
    [string]$outputFile = "watts.csv"
)

# Clear or create log file
"" | Out-File -FilePath $outputFile

try {
    $cmdLine = "`"$exePath`" $argList"
    Write-Host "Executing: $cmdLine"
    $process = Start-Process -FilePath $exePath -ArgumentList $argList -PassThru
} catch {
    Write-Host "Failed to start process. Error: $_"
    exit 1
}

$appPid = $process.Id
Write-Host "Started application with PID: $appPid"
 
$outHead = @()
$outHead += "Timestamp,RemainingCapacity(mWh),DischargeRate(mW)"
$outHead -join "," | Out-File -Encoding utf8 $outputFile
 
Write-Host "Sampling start..."

while (-not $process.HasExited) {
    $outLine = @()

    $timestamp = Get-Date -Format o
    $outLine += $timestamp
    $proc = Get-Process -Id $appPid -ErrorAction SilentlyContinue
    if ($proc) {
        # Battery status sampling
        $powerConsumption = Get-WmiObject -Namespace "root\wmi" -Class "BatteryStatus"
        $remainingCapacity = $powerConsumption.RemainingCapacity
        $dischargeRate = $powerConsumption.DischargeRate
        $outLine += $remainingCapacity
        $outLine += $dischargeRate

        $outLine -join "," | Out-File -Append -Encoding utf8 $outputFile
    }

    Start-Sleep -Seconds $interval
    $process.Refresh()
}

    

Before you run the script, modify the path to ffplay.exe on line 2 to match your installation location.

The battery data is system-based and process-agnostic. Fully charge the battery, close any unnecessary applications, unplug the power cord, and run the script:

    

        
        
.\sample_power.ps1

    

A video starts playing and completes in 30 minutes. When finished, you can find the results file watts.csv in the current directory. The test runs for a longer duration so you can observe a distinct drop in battery remaining capacity.

The script collects remaining battery capacity and discharge rate periodically. You can track the battery remaining capacity to understand the power consumption patterns.

View the results

The output below shows the results from running the x86_64 version of ffplay.exe:

    

        
        Timestamp,RemainingCapacity(mWh),DischargeRate(mW)
2025-08-15T14:42:50.5231628+08:00,48438,4347
......
2025-08-15T15:12:38.2028188+08:00,43823,8862

        
    

The output below shows the results from running the Arm64 version of ffplay.exe:

    

        
        Timestamp,RemainingCapacity(mWh),DischargeRate(mW)
2025-08-15T15:53:05.8430758+08:00,48438,3255
......
2025-08-15T16:22:55.3163530+08:00,44472,7319

        
    

The sample results file is in CSV format. You can open it with spreadsheet applications like Microsoft Excel for better visualization and to plot data analysis charts.

Battery monitoring provides an effective way to measure power consumption differences between x86_64 and native Arm64 applications. By comparing discharge rates, you can quantify the power efficiency advantages that Arm processors typically demonstrate for video decoding workloads.

Wrapping up and next steps

You’ve measured power usage on your Windows on Arm device and can now compare results across builds to see how native Arm64 performance affects battery life. Sharing your findings with the Arm developer community helps others optimize applications for Windows on Arm.