Why is this (displaying a seconds arc) killing my battery?

I added a seconds arc around my round watch faces and it appears to be killing my battery (I'd guess an extra 20% compared to when the seconds display is turned off).  Is it really just that much more?

Thoughts?

Thanks

    function secondsDisplay(dc) {

        var screenWidth = dc.getWidth();
        var screenHeight = dc.getHeight();
        var centerX = screenWidth / 2;
        var centerY = screenHeight / 2;
        var mRadius = centerX < centerY ? centerX - 4: centerY - 4;
        var clockTime = System.getClockTime();
        var mSeconds = clockTime.sec;

        var mPen = 4;

        var mArc = 360 - (mSeconds * 6);

        dc.setPenWidth(mPen);
        dc.setColor(clockColorSet, Graphics.COLOR_TRANSPARENT);
        dc.drawArc(centerX, centerY, mRadius, Graphics.ARC_CLOCKWISE, 90, mArc);

    }

Called by:

    function onUpdate(dc as Dc) as Void {

        notesAlarms();
                
        battDisp();

        dateDisp();

        mainZone(dc);   

        // Call the parent onUpdate function to redraw the layout
        View.onUpdate(dc);

        if (dispSecs && 
                System.getDeviceSettings().screenShape == System.SCREEN_SHAPE_ROUND) {
            secondsDisplay(dc);
        }
    }