u/MaliciousHippie

Before I start, I work in plumbing, in all Alameda and Contra Costa county......

EDIT: BAAQMD FAQ sheet and their website with specifics

The 2027 gas water heater ban is in regards to residential units under 75,000 BTU's (BTU is essentially a measurement of heat output). This means any tank gas water heater under 100 Gallons or IS NOT a high recovery unit will no longer qualify for legal installation. Eventually this will turn into a 175,000 BTU limit for residentials. Installing water heaters from outside state lines is likely going to void any sort of manufacturer/installers warranty too, so keep that in mind,

I am not sure if these things will show up in inspection upon sale or transfer of the property either.... Safe to say though, eventually it will be a requirement, much like a non-broken sewer line (in the yard) is already required and are (supposed) to be inspected before sale of the property.

HOWEVER:

You can still install tankless water heaters in your home, they are often close to 199,000 BTU's, well exceeding the limits imposed by BTU's.

Otherwise heat pump water heaters are going to be your product.

I will lay out the cost/benefit analyses so you can make an informed decision about your property.

BOTH:

• Very high efficiency units, will make your money back within several years.
• As more units are sold, more production will (theoretically) lower actual unit cost as more will be made in bulk since there will be a guaranteed market. These units have been in the market for some time but usually only the most environmentally/spatially minded were early adopters of these products.
• Both will require an electrician to either install a normal GFCI outlet(Gas tankless) or a dedicated 240v hardwired conduit (Electric/Heat pump units).
• Both will have modern monitoring systems/associated apps to manage the units.
• 6 year is the standard warranty for the units aside from the heat exchangers/condenser portions of the tank, which are usually 10yr warranties.
• Due to massive size of heat pump units and different configuration of tankless units, you will likely have to do some re-piping no matter what you choose.

TANKLESS

The Good:

• Comparatively cheaper for the unit itself, but requires additional piping on top of it. Still lower material cost than a straight swap from a traditional GWH to a Heat Pump water heater.
• SMALL form factor, hung onto a wall, can fit in A LOT of spaces. Indoor and outdoor units available, can be installed in most conditions.
• Likely does not require major changes to your electrical system, utilizes power only for monitoring and control of the unit, heat is provided by your gas connection. Just need GFCI outlet.
• GREAT for small homes, if you have 1-2 bathrooms you really don't even need to worry about how your pipes are configured.
• Tankless units are comparatively cheaper than Heat Pump units (most are under 1600 USD and have 10yr warranties on the expensive parts)
• Only heats water WHEN YOU WANT IT (Unless you are using a recirculation line)
• Many models come with internal recirculation, but if you NEED a recirculation system then you should really do it with an external pump.
• Lots of sensors to know if installation was done properly or not so you don't die/fuck something up during installation.

The Bad:

• REQUIRES DEDICATED VENTILATION, CANNOT USE EXISTING VENTILATION DUE TO HIGH HEAT OUTPUT, you don't want your furnace fighting for space in the pipe to push noxious fumes out of your property.
• It is recommended that you install the water heater with access to a 3/4" gas line as close to your meter as possible to ensure the unit is going to get all the gas it wants when it's giving you hot water.
• REQUIRES permitting to do legally, if you need to make major changes to your gas line that will need to be permitted.
• If you are getting a condensing unit (most of them), then you will need to have a good place for potentially acidic condensate to go into, as well as the temperature and pressure relief line. This is IMPORTANT and can fuck up your unit if you ignore it/do it wrong.
• IF YOU HAVE A BIG HOME, then the way your water lines are plumbed will matter a lot. If your plumbing looks kind of line a vine or an assembly line then you'll be in good shape. If you have more than 4 bathrooms you'll need more than the cheapest models, or perhaps even multiple units. If your plumbing looks more like a vascular system where the water heater is the "heart" then you'll probably need to replumb your water lines to ensure hot water is going where it needs to be and isn't being wasted in branch lines and add a return line.

HEAT PUMP WATER HEATERS

The Good:

• Slightly more rebate options, but still not great since those environmental programs got the axe from the federal government.
• CRAZY EFFICIENT, they work like refrigerators in reverse. Their heat pump systems are completely closed too, and don't get serviced. That portion is often warrantied out for 10 years, while the rest will often be a standard 6 year warranty or more.
• Had a guy in Alameda who said between the solar on the roof and the heat pump water heater, they were paying PGE less than $100 a month. This was two adults and a 3 year old. He ended up getting a warranty for a new circuit board. The board wasn't hard to access and took around an hour for a learned professional to replace after shipment. FWIW the board itself was less than $150 for the part should it have been out of warranty.
• NO NOXIOUS VENTILATION REQUIREMENTS
• If the low power heat exchanger/compressor cannot keep up with output demand, then it will activate one of its two electrical heating elements to keep up.
• Usually have options for side inputs if your vertical restrictions are too tight.

The Bad:

• Rather expensive for the unit itself, eventually costs will lower to a more reasonable amount but the lack of early adopters put it into a "specialty item" sort of status.
• BIG AS HELL, like the water inputs stand a good foot taller than the closest comparable old school units. Many homes in the bay area stuff their water heaters in the tightest areas where you cannot even replace the anode rods.
• Makes noise comparable to a refrigerator while the heat pump/condenser unit is active. So don't put it in your living room lol
• Will require a modern electrical system + a dedicated 240V conduit for hardwiring. The electrical heating elements that serve as backups when demand is really high have a 4500W draw per element. There are two. These are NOT constantly active, but are necessary.
  • Plumbers are generally not allowed/not going to rewire your house and breaker box, requiring an electrician too.
  • "But I have old electricals", upgrade that shit ASAP good lord. Don't need to relive '91 out here.
• Pulls residual heat from the surrounding area, requires a certain amount of volume in the area to function properly, so installing it in a somewhat closed off area without good airflow is going to stress the hell out of your unit and you'll see lower efficiency. They usually get put in garages.
  • If you live somewhere really hot, like a garage in Discovery Bay, your unit is gonna be REALLY efficient. If you are in Tahoe or whatever, then maybe don't put it in your uninsulated garage.
• Again, these units are HUGE, depending on where you're getting it installed, you may even have to elevate it on an 18" platform. This applies if the unit is installed in a garage/any area where people are not normally around or can be struck by large objects (like a car in a garage).

OH BUT WATER HEATERS WILL FAIL WHY EVEN BOTHER:
Tank water heaters are supposed to be flushed out once per year, tankless units are supposed to have a descaling solution pumped through them once a year too. Most people ignore these steps and wonder why their units break in 8 years on San Ramon's mineral rich hardwater. If you're on year 4+ and haven't descaled your unit I wouldn't even bother, it might start leaking, seriously.

Recommendations:

Tankless: I've had good experience with Navien and Rinnai units, very good customer service, they overnight parts for warranty calls, and have intuitive apps to control and monitor them. Most models I find are condensing units. If you get a noncondensing unit with serious output expect to need a dedicated 3" to 4" exhaust pipe. Most are 2" PVC exhausts.

Heat Pump: I don't have too much experience with servicing these units, but I know A.O. Smith has a distribution center in the Bay Area where we can often get parts from if its not Saturday/Sunday. They also seem to be the ones who've had heat pumps on the market for the longest too.

DO NOT BUY YOUR WATER HEATER AT HOME DEPOT OR LOWES, SPEND A LITTLE EXTRA AT THE PLUMBING SUPPLY STORE FOR A BETTER UNIT. Rheem is sold at Home Depot and A.O. Smith is sold at Lowes, but they ARE NOT the same units as what you'll find at a professional supply store. Check model numbers if you want to confirm.

EDIT: Removed any sort of recommendations about getting a tankless vs heat pump. I'm laying out the bare good and bad for FUNCTIONAL models, but apparently a lot of people are experiencing issues with their heat pump units. I'll wait for more input before I make any sort of recommendation, budget or not.

EDIT: IF YOU ARE TRYING TO BALL ON A BUDGET, AND YOUR WATER HEATER IS OVER 6-8YEARS OLD I HIGHLY RECOMMEND REPLACING IT BEFORE IT GOES BAD/DEADLINE HITS. Traditional GWH's are pretty cheap right now considering the insane inflation we've been experiencing and are still legal to install.

With this new knowledge, hopefully you'll be able to get a better grasp about what you need/what is possible for you. I wish you all the best of luck.