Hibrid Domestic Hot Water... 50 gallon Natural Gas Water Heater with Electric Primary

[ultrarunner]

The majority of Natural gas use 9 months of the year here is for Domestic Hot water at about $1.65 per Therm

Thinking of going Solar Electric and wondering if it makes sense to go larger to either replace the gas heater with electric

OR

Leave the gas heater in place on a lower setting and augment the hot water recirculating loop with an inline electric heating coil.

Has anyone tried this to save operating costs over the long run?

 

[dnw64]

I'm not familiar with NG prices and efficiency, but I highly recommend taking a look at Heat Pump electric water heaters. Unless you are getting NG/propane/oil for just about free, the HPWH is probably going to beat them out. And with PV it makes even more sense, since the energy is "free" once you recoup the capital.

The primary potential disadvantages of HPWH are:
A) You must provide an environment that maintains 50°F or greater.
B) They produce cool air
C) They have an air filter that must be cleaned regularly (generally at least every 6 months)
D) They produce condensate (if you can't gravity drain it you will need a condensate pump).
E) Generally cost a lot more than a conventional WH

Advantages:
A) 70% less electricity compared to conventional
B) They produce cool air
C) They dehumidify the space
D) Most are "hybrid" and can add resistive heating in times of high demand, so you aren't giving up capacity.
E) Many state energy efficiency programs will provide a rebate, making them cheaper than a conventional WH.

I've purchased three of them, and both my son and daughter have installed them as well. So far (almost three years) they have lived up to expectations.

 

[RNeumann]

Their, currently, isn’t a water heater that is cost efficient enough to justify replacing an existing WORKING water heater. I’ve installed the solar system you describe for a customer and I wouldn’t do it on my place. You aren’t saving money or the planet when it’s all said and done.

When your current water heater craps out consider a tankless heater. That is the “best” current technology for someone looking at cost/therm.

 

[dnw64]

Their, currently, isn’t a water heater that is cost efficient enough to justify replacing an existing WORKING water heater.

Maybe where you are.

Both my son and daughter bought houses that had rented electric water heaters. With the rebate it was a $300 cost to install a HPWH. Both of them had had separate meters for the WH, so they knew for certain the before and after costs of electricity. I don't have the numbers in front of me, but for one of them it was about a 1 year payback, and for the other 6 MONTHS! A good part of the 6 months one was that my son had a very damp basement, and had been running a dehumidifier 24/7. The HPWH drastically reduced the need for separate dehumidification.

Two of the WHs I replaced were also previously rented in a duplex I bought to rent. I'm not privy to Before costs, but because of rebates it was cheaper to buy a HPWH than a conventional WH. If you've ever compared the cost of renting versus buying I think you will agree that buying is better.

Last (personal) case was my own residence. Harder to come up with hard numbers. I went from a 8 year old Propane WH to the HPWH. I figured that the difference in energy costs plus the $100 I could get for my old WH would pay back in under 2 years.

BTW, I have two (electric) tankless water heaters and am underwhelmed by their performance. One of my employees has a propane one and has had numerous problems with it.

Bottom line - there is no "one size fits all" solution to anything. Between needs/wants/desires and local conditions there can be 100 "best" solutions.

 

[ultrarunner]

Their, currently, isn’t a water heater that is cost efficient enough to justify replacing an existing WORKING water heater. I’ve installed the solar system you describe for a customer and I wouldn’t do it on my place. You aren’t saving money or the planet when it’s all said and done.

When your current water heater craps out consider a tankless heater. That is the “best” current technology for someone looking at cost/therm.

Existing 50 gallon natural gas is 20 years old... about the time when the premium heaters fail...

I believe the original owner replaced the anode at least once... there is a receipt taped to the heater.

Edit... just checked and no rebates currently offered... could be because PGE filed for Bankruptcy?

A new Natural Gas is about $500 to buy with tax... we have to buy the low NOX version.

 

[RNeumann]

If this is your Bay Area location then the system I did was about 3 hours south of you- also with PGE. The location (Atascadero) is generally considered warmer and sunnier than the Bay Area.

I just don’t see solar water, or heat pump electric water heater being a saver (planet or money). Based on your latitude and the cost of electricity maybe solar electric for the whole house would pencil for you.

Again, the other option is a tankless. With your mild climate those get installed outside all the time.

And yes, at 20 years old, you are on borrowed time! If you are going to make a change now is a good time. Haha

 

[ultrarunner]

Yep... 20 years and ticking... at least if it lets go it is on concrete should the drain to daylight be overwhelmed...

PGE seems to restrict size of PV system based on historical usage which almost seems to penalize those that have been super frugal... like clothes lines, cold water washing, short showers and such.

Just for kicks... Mom historically uses 360 kWh per month but recently she has been using more heat... and now is 450.

The neighbors with slightly smaller homes use 650 pretty consistently and the other with small kids over 700

The PGE Calc says Mom should have a 2.4 kW array... I think double that would be just about right at 4.8 kW... plus the incremental costs of adding more panels is less if all done at the same time...

She has no South facing... it is either SW or SE dead on... the SE mornings could easily be overcast with marine layer... but the roof plane is clear and unobstructed...

No one has A/C so this is not a factor...

The radiant heat at my new place is a second gas water heater... if there were to be an abundance of Electricity I would imagine the second heater could be electric...

Just running different scenarios right now.