The Voltex hybrid electric heat-pump water heaters include a duct kit accessory that reportedly allows installation in limited-space applications. The kit can be used with all models, including 50-, 66-, and 80-gal. capacities. It also eliminates space requirements by allowing installers to pipe air in and exhaust air out of adjacent rooms. Voltex models have four operating modes that maximize efficiency by matching heating requirements to environmental conditions, including a vacation mode, programmable for as many as 99 days.