Kmart offers this Ultra Plus Powder Laundry Detergent 180-Load Box (17.3 lbs.) for $9.99 ($0.06 per load). Choose in-store pickup to dodge the $17.62 shipping charge. That's $14 off list price, $2 under our mention from April, and tied as the best deal we've seen. This detergent is rated for high efficiency use in all washer types.
Of note, Shop Your Way Rewards members may be eligible for additional credits and discounts.