Gas vs electric hot water tank costs?

[KevinMalone]

My Bradford White gas hot water tank is likely due for replacement soon (~13 years old) so I've been exploring my options. I've already replaced the circuit board on the Honeywell gas control valve as well as the pilot assembly, but annoyingly, I cannot service the anode rod easily as it is integrated with the hot water outlet.

I was considering switching to electric or a hybrid heat pump and ditching gas altogether since we have a heat pump now. Plus, the majority of our electricity is from hydro so I can feel warm and fuzzy about that too. However, when I use various calculators, gas is significantly cheaper to operate. I had assumed that there would be more financial incentive to stop using gas, with the whole push to electrify everything. Am I missing something?

Calculator: https://benhollis.net/experiments/water-heaters/

Inputs:
- Natural gas: $1.39/therm ($13.16/GJ) after taxes + $0.42/day basic charge not accounted for in calculator (ie additional $154/yr cost)
- Electricity: $0.1408/kWh + $0.23/day basic charge (sunk cost)
- Cost of the hybrid heat pump reduced by $1000 rebate
- Labour not considered, likely will be a DIY install
- Prices are in CAD

Our average monthly gas consumption for hot water is 2.4 GJ, but I'm not sure how to adjust the calculator to reflect this, or convert and apply this to electric tanks with different UEFs. At $13.16/GJ and $154/yr basic cost, our annual cost for gas would be ~$530. The replacement gas tank has the same UEF as our current tank.

Regardless, I think I would stay with gas so that we can have hot water during the rare power outage (tank is atmospheric vented), but it would be nice to quantify the differences.

 

[marc1]

Am I missing something?

No you are not. Your math / calculator tool looks roughly correct to me at a quick glance if your input prices are as stated. I have done that exact same calculation, admittedly not recently, and gas always comes out ahead in both provinces I have lived in (AB and BC).

 

[PandaBear]

This is how I typically look at the cost of water heater in gas vs electric: resistance heat is going to be 100% efficient from kwh to water heat - loss to insulation, gas is typically 60% unless you have some new exotic draft fan unit, and it would be no more than 80% unless it is condensing. In my area gas is 5x cheaper than electricity in Therm to kwh conversion, so even if the efficiency of gas is only 60% it will come out ahead for me using gas.

Everywhere I look heat pump is about 2x to 3x more efficient than resistance heat. So in the end it boils down to what else can you do with that environment. Do you need a heat pump or AC to cool off your home anyways, or do you have to heat up the house so the heat pump can heat up your water, would be whether it make sense or not.

1 Therm = 29.3 kwh. Your 14.08c/kwh is about 4.1254/Therm. If your heat pump water heater is 2x efficiency of resistance it would cost 2.063 / Therm in water heating, 3x efficiency of resistance it would be 1.375 / Therm in water heating.

Your gas assuming 60% efficient would be 1.39 / 60% = 2.317 / Therm when factoring in the efficiency cost equivalent to resistance heat that's 100% efficient.

So to standardize them when factoring in efficiency:

100% Resistance electric: $4.125 / Therm
200% Heat pump efficient: $2.063 / Therm + additional heating load if you need to heat your house
300% Heat pump efficient: $1.375 / Therm + additional heating load if you need to heat your house
60% efficient Gas: $2.317 / Therm


What is your location and where do you install your water heater? Do you need to heat the house with a heat pump so your environment have enough heat to pump into the water? That will change the equation further with extra heating load you need from your home heating. This is why heat pump water heater is a no brainer in Florida and maybe Arizona too but not Alaska.

 

[JustinH]

I'd throw another regular gas water heater at it and be done. Is there no additional cost to convert from gas to electric?

 

[UncleDave]

My Bradford White gas hot water tank is likely due for replacement soon (~13 years old) so I've been exploring my options. I've already replaced the circuit board on the Honeywell gas control valve as well as the pilot assembly, but annoyingly, I cannot service the anode rod easily as it is integrated with the hot water outlet.

I was considering switching to electric or a hybrid heat pump and ditching gas altogether since we have a heat pump now. Plus, the majority of our electricity is from hydro so I can feel warm and fuzzy about that too. However, when I use various calculators, gas is significantly cheaper to operate. I had assumed that there would be more financial incentive to stop using gas, with the whole push to electrify everything. Am I missing something?

Calculator: https://benhollis.net/experiments/water-heaters/

Inputs:
- Natural gas: $1.39/therm ($13.16/GJ) after taxes + $0.42/day basic charge not accounted for in calculator (ie additional $154/yr cost)
- Electricity: $0.1408/kWh + $0.23/day basic charge (sunk cost)
- Cost of the hybrid heat pump reduced by $1000 rebate
- Labour not considered, likely will be a DIY install
- Prices are in CAD

View attachment 241034

Our average monthly gas consumption for hot water is 2.4 GJ, but I'm not sure how to adjust the calculator to reflect this, or convert and apply this to electric tanks with different UEFs. At $13.16/GJ and $154/yr basic cost, our annual cost for gas would be ~$530. The replacement gas tank has the same UEF as our current tank.

Regardless, I think I would stay with gas so that we can have hot water during the rare power outage (tank is atmospheric vented), but it would be nice to quantify the differences.

Nat gas usually is cheaper than electricity if you have it available.
Depending on location, one might get a sizable check from a service provider to move to electricity or a hybrid offsetting the cost of purchase.

Of course one cannot make nat gas, but one can make electricity.
As with most things the sensibility of making it onsite varies dramatically.
For those that are already there, or those considering it, electrical devices have radically changed ROI when you make the energy on site.

 

[BMWTurboDzl]

My Bradford White gas hot water tank is likely due for replacement soon (~13 years old) so I've been exploring my options. I've already replaced the circuit board on the Honeywell gas control valve as well as the pilot assembly, but annoyingly, I cannot service the anode rod easily as it is integrated with the hot water outlet.

I was considering switching to electric or a hybrid heat pump and ditching gas altogether since we have a heat pump now. Plus, the majority of our electricity is from hydro so I can feel warm and fuzzy about that too. However, when I use various calculators, gas is significantly cheaper to operate. I had assumed that there would be more financial incentive to stop using gas, with the whole push to electrify everything. Am I missing something?

Calculator: https://benhollis.net/experiments/water-heaters/

Inputs:
- Natural gas: $1.39/therm ($13.16/GJ) after taxes + $0.42/day basic charge not accounted for in calculator (ie additional $154/yr cost)
- Electricity: $0.1408/kWh + $0.23/day basic charge (sunk cost)
- Cost of the hybrid heat pump reduced by $1000 rebate
- Labour not considered, likely will be a DIY install
- Prices are in CAD

View attachment 241034

Our average monthly gas consumption for hot water is 2.4 GJ, but I'm not sure how to adjust the calculator to reflect this, or convert and apply this to electric tanks with different UEFs. At $13.16/GJ and $154/yr basic cost, our annual cost for gas would be ~$530. The replacement gas tank has the same UEF as our current tank.

Regardless, I think I would stay with gas so that we can have hot water during the rare power outage (tank is atmospheric vented), but it would be nice to quantify the differences.

This will make your head spin: Try to factor in the difference in heating/cooling costs when you seal off the vent. Now factor in the additional heating costs caused by your HPWH which is using interior heat to warm water.

IMO the best climate for a HPWH is in a cooling dominated climate. You can throw it a hot garage and it'll be running very efficiently for most of the year.

 

[thastinger]

Including all government interferences, natural gas is still the least expensive BTU between the 3 power sources (electric, propane, NG) spread around the homes in our family.

 

[alarmguy]

Wow, I can see you researched this quite a bit.
I am curious how stable is the electric grid in your area?
If your one to lose power during storms for any period of time, a good old gas tank water heater will provide you will hot water during an outage. Assuming you have public water or a back up gen for a private well.

 

[Rand]

HPWH can come close esp if you have no other gas appliances.
but gas has fast recovery.
I like my HPWH but its not perfect or for everyone.
I use heat pump only mode 100% of the time.
I ran out of water one time and that was after 3 loads of clothes a dishwasher load, 3-showers, a couple 5gal bucket for cleaning etc.. totally untypical use.
but if you manage to totally deplete the hot water recovery can take a few hours.
I run mine at 149f it gives a larger reserve of hot water.. similar to running an air compressor at a higher psi.

 

[KevinMalone]

Thanks for the input everyone.

Yes, there will be additional costs to convert to electricity that I did not factor in out of laziness. It would likely involve ~15' of AC90 10/2 wiring, which isn't cheap nowadays.

Regarding the HP HWT, I don't think it would be a good fit but I included it for comparison. I'm in climate zone 4C based on the IECC map below, with ~2800 heating degree days and ~100 cooling degree days and our hot water tank is located in a conditioned interior space. Even if our heat pump is efficient (3.90 COP at 47F, 2.27 at 17F and 2.17 at 5F), the additional noise from the fan would be a deal breaker.

We were able to take advantage of significant government rebates to convert from our 1980's 60% efficient gas furnace to the heat pump. The heat pump, along with air sealing major leaks, has reduced our average monthly heating costs by 50% while adding air conditioning. The heat pump has already paid for itself after 2 years worth of savings.

 

[PandaBear]

I'm in climate zone 4C based on the IECC map below, with ~2800 heating degree days and ~100 cooling degree days and our hot water tank is located in a conditioned interior space. Even if our heat pump is efficient (3.90 COP at 47F, 2.27 at 17F and 2.17 at 5F), the additional noise from the fan would be a deal breaker.

We were able to take advantage of significant government rebates to convert from our 1980's 60% efficient gas furnace to the heat pump. The heat pump, along with air sealing major leaks, has reduced our average monthly haeting costs by 50% while adding air conditioning. The heat pump has already paid for itself after 2 years worth of savings.

You probably need to add that heating cost of 3.9 to 2.17 COP to your water heater as well then. I think your major savings in the gas furnace to heat pump conversion came from the major air leak sealing, and your gas / electric cost back then were different.

I would say in your case the cost won't add up and the extra noise definitely doesn't.

 

[BMWTurboDzl]

Thanks for the input everyone.

Yes, there will be additional costs to convert to electricity that I did not factor in out of laziness. It would likely involve ~15' of AC90 10/2 wiring, which isn't cheap nowadays.

Regarding the HP HWT, I don't think it would be a good fit but I included it for comparison. I'm in climate zone 4C based on the IECC map below, with ~2800 heating degree days and ~100 cooling degree days and our hot water tank is located in a conditioned interior space. Even if our heat pump is efficient (3.90 COP at 47F, 2.27 at 17F and 2.17 at 5F), the additional noise from the fan would be a deal breaker.

View attachment 241056

We were able to take advantage of significant government rebates to convert from our 1980's 60% efficient gas furnace to the heat pump. The heat pump, along with air sealing major leaks, has reduced our average monthly heating costs by 50% while adding air conditioning. The heat pump has already paid for itself after 2 years worth of savings.

Here's the current map which reflects the as expected warming trend (Ex, Notice the expansion of zone 3 in Tenn, GA, NC, VA). In a few decades you'll be in Zone 3. LOL.

 

[Snagglefoot]

If you ever consider a hot water heat pump you need to consider a few additional things.

1. A hot water heat pump will extract heat and cool down the area it is in. This works really well if the water heater is in a hot garage in South Carolina, but sucks if you are spending money to heat your house and then it takes that energy to heat water.

2. The thing hums. Unlike a air to air heat pump to heat and cool your house, the compressor is indoors. Hmmmmmmmmmmmmmm.

 

[SARG52]

I'll mention the electric units are much easier to do maintenance if you do any upkeep at all.
I do our electric unit every six months which includes replacing the elements and using a wet vac through the bottom element hole to remove the accumulated sediment ...... which in our case is substantial.

 

[KevinMalone]

I'll mention the electric units are much easier to do maintenance if you do any upkeep at all.

This was one of the reasons I considered electric, but it seems clear that staying with gas is the best choice for various reasons.

So, any gas tank recommendations? I chose the John Wood Pro-Line AV50TN in my comparison as it was readily available at my plumbing supply shop, and is most similar to my current 50 gal tank (the smaller 22" diameter is nice for space) with a replaceable anode rod. Unfortunately it also seems to have the same troublesome Honeywell gas control valve, but I'm not sure if the alternatives are any better.

Also, it seems that tanks only come with aluminum anode rods now (cheaper?) while my BW tank came with a longer lasting magnesium anode rod. I noticed that Rheem extends their warranty from 6 to 10 years if you purchase the "Protection Plus" kit, which replaces the hot water outlet with one that has an integrated 22" magnesium anode rod, so that there are two anode rods:



I guess I can achieve the same by replacing the anode rod regularly.

 

[oil pan 4]

And if the heatpump ever needs repair....
Since it's probably going to be a tie at 12 years assuming nothing breaks, tie goes to simplicity.
Gas for the win.

 

[burbguy82]

our electricity is from hydro so I can feel warm and fuzzy about that too.

really?

Is there no additional cost to convert from gas to electric?

Sure, running a dedicated 40-60 amp circuit to the electric heater is not free.

I would just replace the unit you have with a new one. Call it a day, in the long run it will be the cheapest.

 

[Rand]

And if the heatpump ever needs repair....
Since it's probably going to be a tie at 12 years assuming nothing breaks, tie goes to simplicity.
Gas for the win.

not really a tie. hpwh vs electric for me full payback in less than 3 years conservatively. (on a regular priced HPWH)
And dehumidifies my basement which is needed 8 months of the year. = basically net 0 energy for hot water 8 months of the year vs running a dehumidifier.
I also have extremely cheap natural gas so heating the house is still very inexpensive.
Last year's january gas bill was around $70 with a 44$ connection fee= usage of $26
The HPWH I had previously died due to bad installation and rusted out at the cold water inlet. 8 years IIRC.. the heat pump part was fine.

A direct vent natural gas water heater was 2900 installed... I bought and installed the HPWH for $350

In many cases they are a good option.

 

[JeffKeryk]

@Kantaro have you considered a tankless? I installed one years ago. My guess is prices have continued to drop.

 

[KevinMalone]

@Kantaro have you considered a tankless? I installed one years ago. My guess is prices have continued to drop.

I wrote them off assuming they would cost significantly more, but it's not as bad as I thought. ~$2500 for a Rinnai 199K BTU gas tankless but still more costly than a gas tank. The installation would also be a lot more involved as my current gas tank is atmospherically vented. Seems like a decent choice if space is an issue though. They are surprisingly close to the hybrid HP tank!