Water heaters
SANCO2 CO2 Heat Pump Water Heater, 83 gal split system
Prices are the equipment only — the appliance, before install labour. Every product in this catalogue currently has at least one real, seller-observed equipment price (see the SKU verification and price observation notes on each product). Get contractor quotes for the install itself, especially for anything needing new electrical circuits or condensate drainage.
Split-system CO2 refrigerant heat pump water heater rated to operate down to -25°F ambient, with a UEF of 3.75.
Our take
This is the answer to the heat pump water heater's biggest weakness. Conventional units put the compressor on top of the tank indoors, which is why they need a big warm room and why they fail in cold garages. SANCO2 puts the heat pump outside like a mini-split and runs CO2 as refrigerant, so it keeps working at -25°F and produces water hot enough that it doesn't need resistance backup at all. It costs roughly double and needs a specialist installer. In climate zone 6 or colder with no good indoor location, it may be the only real option.
Best for
Cold-climate homes with no suitable conditioned space for a conventional heat pump water heater.
Watch out for
Specialist install, limited contractor familiarity, and a price that only makes sense when the alternative genuinely doesn't work.
What sellers are actually charging
Real listings, read on the date shown — none currently in stock at the observed price. Prices change — click through to check before you act on any of them.
| Seller | What you get | Price | Stock | Seen |
|---|---|---|---|---|
| SkipTheWarehouse.com
online retailer |
equipment system | $7,355 | out of stock | 2026-08-16 |
Equipment price is not installed price. The listings above are what the hardware costs. Installation — labour, electrical, refrigerant lines, permits, removing the old system — is typically a similar amount again, and varies more between contractors than between brands. Where we have an installed figure it is labelled as such and comes from someone who actually installs.
What owners and installers report
Collected from trade forums, owner communities and video reviews. Every report links to the original. We synthesise and quote briefly — we don't republish other people's writing.
Reliability and failures
What breaks, when, and how often — from people several years in.
Thin evidence — too few independent reports to call this a pattern. Shown because it may still be worth asking your contractor about.
Two upper-Midwest project installations reportedly froze after heat-tape failures; one outdoor unit required complete replacement.
“both of them had heat tape failures” — tomb_d trade, Nov 22, 2023 01:55pm
Reported on the SANCO2 line; size not stated — included here because it's the same family and counts toward the totals above.
https://www.greenbuildingadvisor.com/article/sanco2-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2023-11-20 · read it in context
An operator reports zero issues over more than three years across several SANCO2 systems serving multifamily buildings and a home.
“Absoluely zero issues” — user-6533823 trade, Nov 22, 2023 01:56pm
Reported on the SANCO2 line; size not stated — included here because it's the same family and counts toward the totals above.
https://www.greenbuildingadvisor.com/article/sanco2-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2023-11-20 · read it in context
A Tallahassee owner reports quiet operation, high efficiency, and more available hot water than the natural-gas unit the SANCO2 replaced.
“It's quiet, efficient and produces more hot water than we had with a NG water heater it replaced.” — KLWTallahassee trade, Apr 16, 2024 12:07am
Reported on the SANCO2 line; size not stated — included here because it's the same family and counts toward the totals above.
https://www.greenbuildingadvisor.com/article/sanco2-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2023-11-20 · read it in context
A coastal Northern California owner reports strong efficiency, quiet operation, fast recovery, and high satisfaction after slightly more than a year.
“I couldn't be happier with it” — mibici trade, Nov 29, 2023 06:57am
Reported on the SANCO2 line; size not stated — included here because it's the same family and counts toward the totals above.
https://www.greenbuildingadvisor.com/article/sanco2-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2023-11-20 · read it in context
Cold-weather performance
Whether the unit actually keeps the house warm when it gets cold, and how hard backup heat has to work. On a heat pump water heater this is whether it stays in efficient heat-pump mode or falls back to resistance heat in a cold space.
Rated to operate to -25°F, but early units had freezing problems in the outdoor compressor loop; the maker retrofitted heat-tape insulation and freeze-protecting relief valves. The remaining failure mode: a power outage during extreme cold can still freeze the compressor even with the tape installed — an installer recommends backup power for the unit.
“the compressor pump will freeze, even when protected by the relief valves” — forum participant trade, 2023-11-20
https://www.greenbuildingadvisor.com/article/sanco2-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2023-11-20 · read it in context
Installer/owner consensus: the Sanden makes hot water down to -20°F and can lift incoming water nearly 100°F even at 5°F, but efficiency collapses in the cold — COP falls to roughly 2-3 below 10°F versus 5-6 in warm weather.
“COP in the 2-3 range when below 10F” — forum participant, 2021-05-01
https://www.greenbuildingadvisor.com/question/sanden-sanco2-vs-hybrid-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2021-05-01 · read it in context
A commenter argues the SANCO2's remote outdoor compressor pulling from outside air (vs. a standard HPWH pulling from already-cooled basement/utility-room air) gives it a real cold-climate advantage.
“The Sanden would likely be the winner just based on the temperature of the source air.” — severaltypesofnerd, 2021-05-10
Reported on the SANCO2 line; size not stated — included here because it's the same family and counts toward the totals above.
https://www.greenbuildingadvisor.com/question/sanden-sanco2-vs-hybrid-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2021-05-01 · read it in context
A commenter warns the SANCO2's remote tank (unlike an integrated-tank hybrid) is exposed to a freeze risk during a power outage that a standard hybrid HPWH doesn't share to the same degree.
“When the power fails and the former is destroyed by freezing, the Rheem will be significantly better.” — Jon_R, 2020-05-26
Reported on the SANCO2 line; size not stated — included here because it's the same family and counts toward the totals above.
https://www.greenbuildingadvisor.com/question/sanden-sanco2-vs-hybrid-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2021-05-01 · read it in context
Running cost as experienced
Bills owners report after switching, against what they expected.
Thin evidence — too few independent reports to call this a pattern. Shown because it may still be worth asking your contractor about.
A homeowner who had just installed a Sanden (SANCO2) heat pump water heater (140F output, 80-gallon tank) shared measured summer energy-use figures: roughly $30/month without a recirculation pump running, rising to about $36-57/month depending on how much a recirculator was used, compared to about $60/month they had been paying for gas with their old unit. They also noted no repairs were needed on the sealed outdoor unit so far.
“Energy use, summer outdoor temperatures: Without recirculator 20 kWh/7-days (85kWh/mo or around $30/mo)... with recirculator 60-min/day (4x15min) 38 kWh/7-day (162kWh/mo or ~$57/mo) vs. old gas unit $60/month in gas.” — severaltypesofnerd homeowner, 2021-09-11
Sanden Heat Pumps · GreenBuildingAdvisor Q&A · 2021-09-12 · read it in context
An owner who replaced a leaking Stiebel Eltron with a SANCO2 reports at least a 20% efficiency improvement and lower noise after one year.
“at least 20% more efficient” — scsiguy trade, Nov 21, 2023 12:08pm
Reported on the SANCO2 line; size not stated — included here because it's the same family and counts toward the totals above.
https://www.greenbuildingadvisor.com/article/sanco2-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2023-11-20 · read it in context
Controls and compatibility
Thermostat integration, communicating-system lock-in, firmware, and whether the equipment achieves its rated staging in practice. On tankless water heaters this also covers ignition delay and the 'cold water sandwich' effect.
Thin evidence — too few independent reports to call this a pattern. Shown because it may still be worth asking your contractor about.
A 17-month owner of a Sanden (SANCO2) heat pump water heater reported that after a multi-hour utility power outage, the unit failed to automatically restart and the household didn't notice until the hot water ran cold; the fix was simply opening the top (4 screws) and pressing the reset key a few times, with no parts or service call needed. Aside from this one glitch, the owner described the unit as reliable and said they remain happy customers, though they flagged an ongoing concern about freeze protection during a long power outage in cold climates.
“Once, after a utility power outage of several hours the heat pump failed to kick back in by itself and we didn't catch on until the hot water ran cold. The fix was 4 screws off the top and press the key a few times. Otherwise it has been reliable and we are happy customers.” — palmerenh homeowner, 2021-09-12
Sanden Heat Pumps · GreenBuildingAdvisor Q&A · 2021-09-12 · read it in context
Noise in real installations
What owners report hearing, versus the manufacturer's rated sound level. Rated figures are measured under controlled conditions that rarely match a real installation.
Thin evidence — too few independent reports to call this a pattern. Shown because it may still be worth asking your contractor about.
Because the compressor sits outdoors (split system), owners report no indoor noise or cold-air dumping — the complaint that dogs standard indoor-cabinet heat pump water heaters like the ProTerra.
“extraordinarily happy” — Mibici trade, 2023-11-20
https://www.greenbuildingadvisor.com/article/sanco2-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2023-11-20 · read it in context
Sources are linked so you can verify any of this yourself. We don't mirror content — Amazon in particular permits no republication of review text, so where we use retailer data we show the aggregate rating and link out. How we collect and weight this →
Before you buy — install and sizing lessons
Reported issues about installation, sizing, or the dealer/installer — not the equipment itself. These don't affect the ratings above; they're what to ask your contractor about before you sign a contract.
Installation and commissioning · house fit
Split-system design requires more materials/labor than a unified HPWH, though the article calls it 'basic stuff for plumbers'. Cost ($5,000-$6,000 installed, per the article) is the recurring adoption barrier.
"basic stuff for plumbers" — forum participant trade, 2023-11-20
https://www.greenbuildingadvisor.com/article/sanco2-heat-pump-water-heater · GreenBuildingAdvisor Q&A · 2023-11-20 · read it in context
Compare against
GE Profile GeoSpring Smart Hybrid Heat Pump Water Heater, 50 gal
GE's flagship heat pump water heater, relaunched under the Profile line with FlexCAPACITY mixing and Wi-Fi control. ENERGY STAR-certified at UEF 4.50 -- the highest efficiency figure in this catalogue at any size.
GE Profile GeoSpring Smart Hybrid Heat Pump Water Heater, 80 gal
80-gallon version of the same Profile GeoSpring Smart Hybrid platform as the 50-gallon model -- same UEF 4.50, larger first-hour rating.
Rheem ProTerra Hybrid Heat Pump Water Heater, 50 gal
The default heat pump water heater for most US households: 50 gallons, UEF 3.75, widely stocked and widely serviced.
Rheem ProTerra Hybrid Heat Pump Water Heater, 80 gal
80-gallon version of the ProTerra, UEF 4.0 — the highest efficiency in the mainstream heat pump water heater market.
Before you buy this
Ask for the first-hour rating, not just tank size, and check it against your household's simultaneous demand — showers and laundry at the same time — rather than headcount alone. If it's a heat pump water heater, confirm the room has enough air volume (or a duct kit) that it won't spend winter on resistance backup, and that there's a real route for condensate, not just a nearby floor drain. Confirm the panel has spare 240V capacity. And if you're removing a gas unit that shared a flue with a furnace, ask what happens to that flue once your water heater's draft is gone — an orphaned flue can backdraft.