A. O. Smith Voltex AL Review: Quiet and Compact, Fragile Compressor

On paper the A. O. Smith Voltex AL (HPTS-50) is the heat pump water heater that fits where others won't: it needs only 450 cubic feet of room, sits against walls with zero side and back clearance, and A. O. Smith rates it at 45 dBA. ENERGY STAR gives the 50-gallon 3.80 UEF and the lowest estimated electricity use of the Medium-draw 50-gallon tanks we compare. We'd still only buy one if that small-room fit is the deciding factor and your installer will stand behind a swap.

The reason is reliability. Owners report compressors that stop moving heat, refrigerant leaks and error 084 in the first year or two often enough that we treat it as a known weakness, and some replacement units have failed the same way. A. O. Smith replaces the tank under its 10-year parts warranty, but after the first year the labor to swap a water heater that ships at nearly 200 pounds is yours, and owners report paying $500 to more than $1,000 each time. Where a 700-cubic-foot space is available, we'd buy the Rheem ProTerra or the GE Profile instead.

A. O. Smith doesn't sell this tank on Amazon, so we link its own page and earn nothing on it. The Amazon picks below are the comparable tanks you can buy there.

Where it shines

• Small spaces: 450 cubic feet of enclosed room, 84 with a louvered door, and no minimum at all with inlet and outlet ducting through its integrated duct adapters.
• Efficiency: 3.80 UEF on the 50 and an estimated 831 kWh a year, about 2.3 kWh a day.
• Quiet: A. O. Smith claims 45 dBA, and owners who live with one describe a light hum they don't hear outside the room.
• Plumbing flexibility: water connections on the top and the front, and leak detection with an optional automatic shutoff valve.

Where it doesn't

• Compressor failures: the single biggest complaint, often within two years and sometimes on the replacement unit too.
• Smaller first-hour rating: 65 gallons on the 50, the lowest of the 50-gallon tanks in our comparison.
• Electric mode times out: you can lock out the heat pump for 1-7 days at most, so a dead compressor means resetting it every week.
• The app: owners call it laggy and confusing, and its hot water graph read backwards after one update.

Which Voltex you are looking at

A. O. Smith sells several heat pump lines with overlapping names, and owner reviews mix them up. Compare model numbers, not the Voltex name.

The older HPTU stops using its heat pump below 45°F, eight degrees sooner than the HPTS, so a winter complaint about a pre-2022 Voltex in a cold garage may not apply here. A. O. Smith's own product page lists the HPTS-50 at 3.88 UEF; its spec sheet and ENERGY STAR say 3.80, and 3.88 belongs to the HPTS-80.

The ratings, size by size

ENERGY STAR figures. The jump in kWh on the 66 and 80 comes from the heavier test draw, not lower efficiency. A plain electric tank can't top 1.0 UEF, so at 3.80 the HPTS-50 uses roughly a quarter of the electricity for the same hot water on the DOE test. All three use 4.5 kW elements on a 30 A, 240V circuit, and the heat pump works only with surrounding air between 37°F and 120°F and tank water averaging at least 55°F; outside that window the elements take over.

Getting enough hot water out of it

The 50-gallon's 65-gallon first hour is enough for two people and tight for four. Owners who are happy with theirs tend to set the tank to 140°F and add a thermostatic mixing valve, which the manual recommends, so the taps get a safe temperature and each gallon goes further. Hybrid is the default mode; Heat Pump mode is the cheapest to run and the slowest to recover. If you have a big family or a soaking tub, start at the 66.

One startup tip worth knowing: filling a new tank with very cold water and running heat-pump-only can trip a compressor error on day one. An owner whose HPTS-66 did exactly that cleared it by heating the first tank on Hybrid or Electric, then switching, and had no further errors for months.

What the install requires

This is a plumber and electrician job in most places, and many towns require a permit for a water heater replacement. A. O. Smith's manual suggests a qualified installer if you're unsure. What the job has to provide:

• Circuit: a 208/240V supply with a 30 A breaker, per the spec sheet.
• Space and air: 450 cubic feet enclosed, 84 with a fully louvered door or upper and lower louvers of 130 sq in each, or ducting in and out. The 50 stands 63 in tall and 22 in wide and ships at 196 lb.
• Condensate: a drain for the non-acidic condensate, or a condensate pump if there isn't one.
• Warranty conditions: a drain pan where a leak would cause damage, a new T&P relief valve piped to a drain, and an expansion tank on a closed system. The warranty requires all three where they apply.
• Recirculation: A. O. Smith's manual doesn't recommend this heater on a recirculation loop and warns that poorly insulated recirc piping can keep it running continuously.

If there's no floor drain nearby, a small pump such as the Little Giant VCMA-15 handles the condensate.

The reliability problem

Here's the pattern, and it's consistent enough that we won't soften it. The heat pump stops heating, usually in the first or second year: exhaust air that should be noticeably colder than the room comes out at room temperature, recovery slows to a crawl, and sometimes the control shows error 084 for the compressor. Diagnosis tends to find a refrigerant leak or a dead compressor. The sealed system isn't repaired in the field; A. O. Smith authorizes a whole new tank.

Some owners are on their second, third or fourth unit, and replacements have failed the same way. Others report two or three trouble-free years, heat-pump-only operation and electricity use in line with the rating, so this isn't every tank. But the failure turns up too often, among owners who name the HPTS and owners of other recent A. O. Smith hybrids, to treat it as bad luck.

What makes it expensive is labor. The warranty supplies a replacement tank or part for 10 years but pays onsite labor only in the first year, through a factory-authorized servicer. After that, removing and refitting a full water heater runs several hundred to over a thousand dollars by owners' accounts, and an installer who didn't sell you the unit may not want the job. If you buy one, buy it from an installer who'll handle warranty swaps at a fixed price, file any claim inside the first 12 months if the heat pump seems weak, and keep the install invoice.

The warranty

A. O. Smith's residential electric warranty covers the HPTS for 10 years on the tank and 10 on parts for the original owner, with onsite labor in the first year only. Outside a single-family home the warranty drops to one year. It applies only to an install that follows codes and the printed instructions, with a drain pan where needed, a new CSA-certified T&P valve and an expansion tank on closed systems, and it's voided if you skip the maintenance in the manual: flushing, cleaning the air filter and condensate pan, and inspecting the anode after six months and yearly after that. You'll need proof of purchase and the installation date to claim.

How it stacks up

Fifty-gallon heat pump water heaters, ENERGY STAR figures. Compare kWh only between tanks tested at the same draw pattern.

• Rheem ProTerra: slightly more efficient and better documented, with a bigger owner community, but louder and with its own control-board record. It wants 700 cubic feet unducted. Our ProTerra review covers it.
• GE Profile GeoSpring: the most efficient 50-gallon on ENERGY STAR's list and the one owners describe as quieter than the Rheem; the pick for a tank near bedrooms. Not on Amazon.
• Rinnai REHP50: the Amazon-sold option with the biggest first-hour rating here, 73 gallons, and a listing that promises 10 years on tank and parts and 1 year of labor. Less owner history, and one Bay Area owner of the 80-gallon reports it leaning on its elements in a cool garage.

Our call

Buy the HPTS only when its space rules decide it: a closet, a tight utility room or a spot against a wall where a 700-cubic-foot tank won't work, with an installer who'll do a warranty swap at a fair price. Set it to 140°F with a mixing valve, keep the filter clean, and watch the exhaust temperature in the first year.

Everywhere else, the GE Profile is the tank we'd want near living space, and the Rheem ProTerra or the Amazon-sold Rinnai are the alternatives with fewer reported compressor failures. Whatever you buy, budget for the labor of a swap, because no heat pump water heater on this list pays for it after year one.