Not all plumbers do heat pumps well. Make sure to ask any contractor how many they have done, and make sure they are happy with HPWH. PCE has a list of contractors in San Mateo. So does TheSwitchIsOn, and you can try Yelp and other online sources. PCE has a list of installers of rebated heat pumps in 2021, the top three 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 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 and Peninsula Clean Energy.
Prices vary from about $1,700 to $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 ($1730 at Home Depot) with a first hour rating of 67 gallons, while their 80 gallon version costs $2497 and has a first hour rating of 87 gallons.
Heat pumps vary in efficiency, measured by UEF. Bigger tanks usually have higher UEF, maxing out at 4.0. Some 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, with newer releases from GE and LG. 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.
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.