Magento count configurable product quantities

$product_qty = (int) Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getQty();

$prod = $_product->load($_product->getId());
$conf = Mage::getModel('catalog/product_type_configurable')->setProduct($prod);
$col = $conf->getUsedProductCollection()->addAttributeToSelect('*')->addFilterByRequiredOptions();

$total_qty = 0;

foreach ($col as $sprod){
    $sprod = $_product->load($sprod->getId());
    $qty = intval(Mage::getModel('cataloginventory/stock_item')->loadByProduct($sprod)->getQty());
    $total_qty += $qty;
}