In San Mateo county, a good starting point is the BayRen site to search for their approved contractors. There are about 38 listed for San Mateo County. When the TECH rebates come out, you'll also need to check that your contractor is registered with them.
BayREN has approved these contractors, but you should still make sure they are experienced and comfortable with doing the job. Peninsula Clean Energy have a list of water heaters they rebated in 2021, and the most common installers were EmeraldECO (Redwood City), Shoreway Plumbing (Redwood City) and Alternative HVAC Solutions (San Carlos). There's quite a bit of price variation, and some suggestion that contractors are charging more because of the big rebates, so it's well worth calling around. If you can send a picture of where your gas heater is installed, and one of your electrical panel, that can help get an early accurate quote.
There are also some new recently-started free 'concierge' services that will help you pick a contractor and take care of most of the decision making for water heating and other electrification. They include Quit Carbon in the Bay Area.
Prices vary from about $1,700 to over $2,800. Key factors are the size of the water tank, the power of the heat pump and other bells and whistles.
Tanks are usually 55 to 80 gallons. Bigger is more expensive, costs a bit more to run, and allows for everyone to have a long shower at once without running out of water. You can simply get the same capacity as your current one, or can look up this calculator to see if that's still the best size. Since the heat pump is less powerful than gas, some people upsize 10 gallons or so from their gas heater size, and larger ones tend to be a bit more energy-efficient.
The power of water heater is shown by its "first hour rating", the number of gallons of fully hot water it can deliver in one hour, starting with a full tank. For instance Rheem's Proterra line has a 50 gallon heater ($1700 at Home Depot) that has a first hour rating of 67 gallons, while their 80 gallon version costs $2690 and has a first hour rating of 87 gallons.
Heat pumps vary in efficiency, measured by UEF. Bigger tanks usually have higher UEF, with a 4.0 being the record. BayREN rebates require a UEF of 3.1, which some of the smaller units (40 gallon tanks) don't reach.
The main brands of heat pump water heater are Rheem, Rudd (owned by Rheem), A. O. Smith, Stiebel Eltron, Bradford White. SANCO2 is a specialist brand with an outside compressor and uses CO2 for refrigerant, which is excellent in cold temperatures but about twice the price of other units. Rheem is often the cheapest and has a 120V model, but some recent units have been reported as extra noisy, so check with your contractor as to the current situation.
You can get free expert help from BayRen where a Home Energy Advisor can talk you through rebates, finding a contractor and getting the job done.
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Back to the San Mateo County Guide to Climate-Friendly Water Heating.