Equipment · July 26, 2022
Heat-pump water heaters, without the brochure
They cut water-heating energy sharply when the closet, the condensate, and the noise are designed. They disappoint when they are treated like a drop-in tank.
8 minute read · Anchors Aweigh Energy
A heat-pump water heater (HPWH) does not make heat with a resistance element as its first move. It moves heat from the room into the tank. That is why the efficiency numbers look almost rude compared with a gas tank or a plain electric one — and why the room it lives in is part of the appliance.
What they are good at
- Cutting water-heating energy use by half or better in a typical Southern California climate.
- Pairing cleanly with rooftop solar, because they run on electricity and can be scheduled.
- Meeting current Title 24 and many reach-code or incentive pathways that are pushing the state off gas water heating.
What they are picky about
They need volume to pull heat from, or a louvered door and a path to another space. They make a compressor sound — quieter than a window AC, louder than a gas tank that sits there. They make condensate that has to go somewhere that will not stain a garage slab. They do not love a sealed 12-square-foot closet with a solid door and no drain.
If your contractor says “it fits the old footprint,” ask about air volume, condensate, and whether the unit will be in heat-pump mode or kicking over to resistance because it is starving for air. Resistance mode is how a wallet-pump is born.
Code and HERS
On many new homes and alterations the water heater is part of the Title 24 performance run, and some jurisdictions or programs want a HERS verification of the installation. We will tell you if your particular job triggers that, and we will test it if it does.
An HPWH is one of the few retrofits that often pays on the bill and on the carbon ledger at the same time. Install it like equipment, not like a box that happens to fit the closet, and it will behave.