Natural Gas vs Heat pumps for heating

[jjrandorin]

This is probably where having a separate gas and electricity provider is better. We here in SoCal Edison territory have SoCal Gas for gas and Edison for electricity.

I personally am really glad I am neither in PGE or SDGE territory, here in CA. My monthly Natural gas bill for 9 months out of the year is <$30 a month. My Clothes dryer is Natural gas (with no hookup for an electric dryer in my laundry room which I found strange for a home built in 2007 but /shrug).

Nov - Jan when I need to run the heating, its 70-80 a month those months.

 

[h2ofun]

How much was the cost to convert over to mini splits? The quotes I got for a total 6 ton were insanity. Almost $45k to go ductless with all the installation being "extra tricky". That was almost 2x normal HVAC.

Lets see, I have 10 heads, 4 compressors, about 10 tons, and yea about 40K. You are not counting if you started from scratch, the cost of putting in all the ducting would make your "normal" HVAC way way more expensive. We LOVE our mini splits. 100% zoned. NO loses from duct work, and wasted space taken in our house. But it is tough to justify if you are only replacing the multipack, and not all the ducting.

 

[wwu123]

I also have a Navien tankless unit. It has a built-in recirculation pump and an internal small buffer hot water tank so there is always a little bit of hot water available even at small flow rates. It monitors the buffer tank temperature and turns on the heater and recirculation pump as necessary to keep it hot. It has an option to learn your habits and will turn on the recirculation system when it predicts you are going to use hot water. There is a slight loss of efficiency this way but it is worth the comfort.

Ah, that's pretty sweet! Prior to going tankless, my old gas tank water heater had a gravity recirculating loop plumbed in. Completely passive (no pump), it worked surprisingly well, but the tank has to be in a basement or crawlspace below the faucets. Anyway that slow recirculation wouldn't work with the Noritz.

I've installed a compromise by putting in a pair of EcoSmart electric on-demand heaters closer to the kitchen and bathroom taps. They turn on as soon as the water flows, so buffer the cold water sitting in the pipes until the hot tankless water flushes them out. Then turn off at that point. They're more powerful than the undersink ones - 30A, 240V, bigger too so have to be in the crawlspace - I could get 3/4 of the way to the kitchen sink, though only halfway to the bathrooms before the pipes disappear into the studs. Still, 15 seconds to hot water versus 30 seconds is still a big difference for morning showers.

Wasteful 100% resistance heat, to be sure, but it's only a few seconds til the pipes are flushed, and just a few times a day. Far less cold water going unused down the drain, and the vast majority of the water heating is still from the gas tankless. I think these particular EcoSmart units were designed to boost the capacity of a conventional tank heater, when you start depleting the tank, it "boosts" the lukewarm temp for a while longer - I'm using them differently, but hence why they're OK with hot water on their input side as well.

 

[RKCRLR]

Ah, that's pretty sweet! Prior to going tankless, my old gas tank water heater had a gravity recirculating loop plumbed in. Completely passive (no pump), it worked surprisingly well, but the tank has to be in a basement or crawlspace below the faucets. Anyway that slow recirculation wouldn't work with the Noritz.

I've installed a compromise by putting in a pair of EcoSmart electric on-demand heaters closer to the kitchen and bathroom taps. They turn on as soon as the water flows, so buffer the cold water sitting in the pipes until the hot tankless water flushes them out. Then turn off at that point. They're more powerful than the undersink ones - 30A, 240V, bigger too so have to be in the crawlspace - I could get 3/4 of the way to the kitchen sink, though only halfway to the bathrooms before the pipes disappear into the studs. Still, 15 seconds to hot water versus 30 seconds is still a big difference for morning showers.

Wasteful 100% resistance heat, to be sure, but it's only a few seconds til the pipes are flushed, and just a few times a day. Far less cold water going unused down the drain, and the vast majority of the water heating is still from the gas tankless. I think these particular EcoSmart units were designed to boost the capacity of a conventional tank heater, when you start depleting the tank, it "boosts" the lukewarm temp for a while longer - I'm using them differently, but hence why they're OK with hot water on their input side as well.

I had a recirculation system with pump put in when I built my house. But the plumber didn't do a good job of insulating the return line and it was operating in gravity mode even when the pump wasn't on (the heater is in a walk in area on the lower level). My heater was using a lot of propane so I insulated the lines better and pretty much stopped the gravity flow. My old electric recirculation pump is still in the return line but I don't use it anymore because of the recirculation pump in the Navien heater.

 

[holeydonut]

Lets see, I have 10 heads, 4 compressors, about 10 tons, and yea about 40K. You are not counting if you started from scratch, the cost of putting in all the ducting would make your "normal" HVAC way way more expensive. We LOVE our mini splits. 100% zoned. NO loses from duct work, and wasted space taken in our house. But it is tough to justify if you are only replacing the multipack, and not all the ducting.

Well yeah, I'm not budgeting the cost of the ducts since... they're on the house. So the economics of an HVAC replacement for me (and I suspect most homeowners with detached houses in California) are highly skewed into keeping normal furnace/outdoor-condensers.

Stopping using the ducts makes no sense without some incentive to move to minisplits. Plus, I'm not going to put up with the "what is this, a Best Western or a house? You can take these ugly minis splits and cram them up your _____"

Charging homeowners 40% more for NG isn't really a "behavior incentive" since such policy only serves to obliterates homeowners who cannot afford to drop $40k+ or cannot afford $500 per month heating bills.

 

[jboy210]

That's the nice thing about the hybrid system, you can have the economy of a heat pump but have furnace operation when you feel like it. And it is definitely more comfortable during the defrost cycles.

So does it switch to heating via the heat pump once you get the house up to temp or is heating always gas?

 

[wwhitney]

While performance improvements in heat pumps show up first in mini-splits, they are also available in conventional central systems. And a "mini-split" outdoor unit can be paired with a high static pressure air handler to replace a central system. Possibly also with one or two additional ductless heads if desired to address shortcomings of the existing ducts, or to condition an addition.

Cheers, Wayne

 

[RKCRLR]

So does it switch to heating via the heat pump once you get the house up to temp or is heating always gas?

The default is heat pump but you can select the energy source from the wall control.
It will first try to use the heat pump but if you increase the temperature by a few degrees it will switch to the furnace. And if it can't recover from a set-back temperature on heat pump it will switch to the furnace. I have the furnace locked out until it gets below 40F out and the heat pump locked out once it gets down to 25F, but all of these settings are adjustable.

 

[jboy210]

I am curious to know what impact switching to heat pumps for heating has on the amount of electricity the home uses in the winter. Because of shading, we generate no more than 20 kWh/day on winter days. Right now this is fine because we have gas heat.

 

[miimura]

I also have a Navien tankless unit. It has a built-in recirculation pump and an internal small buffer hot water tank so there is always a little bit of hot water available even at small flow rates. It monitors the buffer tank temperature and turns on the heater and recirculation pump as necessary to keep it hot. It has an option to learn your habits and will turn on the recirculation system when it predicts you are going to use hot water. There is a slight loss of efficiency this way but it is worth the comfort.

@wwu123 the other thing not mentioned yet about the recirc pump built into the Navien unit is that it is variable speed. When you first start to use hot water, it fires up the heater and then runs the pump at a high flow rate to push the newly heater water through the pipes as fast as it can. When it senses that the return water is hot enough, it slows down or stops, allowing the just the user flow of hot water to go through the system.

It is important to insulate your hot water pipes, including the return, as much as possible or this will lead to significant energy loss. If I had more time when my house was under construction, I would have gone along all the pipes and filled in the gaps between the closed cell foam pipe insulation with spray foam.

 

[h2ofun]

Well yeah, I'm not budgeting the cost of the ducts since... they're on the house. So the economics of an HVAC replacement for me (and I suspect most homeowners with detached houses in California) are highly skewed into keeping normal furnace/outdoor-condensers.

Stopping using the ducts makes no sense without some incentive to move to minisplits. Plus, I'm not going to put up with the "what is this, a Best Western or a house? You can take these ugly minis splits and cram them up your _____"

Charging homeowners 40% more for NG isn't really a "behavior incentive" since such policy only serves to obliterates homeowners who cannot afford to drop $40k+ or cannot afford $500 per month heating bills.

Yea, totally agree. I only did mine since my systems were removed, and all the ducting under the house. So I got lucky and could start over. Folks building new homes with the old duct design I do not understand

 

[h2ofun]

I am curious to know what impact switching to heat pumps for heating has on the amount of electricity the home uses in the winter. Because of shading, we generate no more than 20 kWh/day on winter days. Right now this is fine because we have gas heat.

It goes up a LOT. Just depends on things like how big your house, how cold outside, how warm you want it, etc. Bottom line solar is worth basically nothing for my heat pumps during the winter.

 

[lavalamp425]

I am curious to know what impact switching to heat pumps for heating has on the amount of electricity the home uses in the winter. Because of shading, we generate no more than 20 kWh/day on winter days. Right now this is fine because we have gas heat.

If I run the heat pump as much as I can, it roughly doubles my winter electricity usage compared to not using the heat pump at all. In reality I tend to balance heat pump and furnace usage for comfort reasons, so my electric bill is higher than before but not double.

 

[BGbreeder]

I'm in the northeast, a short drive from the Canada border (yup, it can get cold for long periods). We have an oil boiler with a SuperStor hot water storage tank for potable and baseboard forced hot water for heating. About a decade ago, installed mini-splits for summer A/C. Last year installed solar & PWs. Now we use the mini-splits as primary heating with fallback to oil heat when it gets to ~< 10°F. We don't bank quite enough over the summer to pay through the winter mini-split heating bill, however our overall energy cost is lower than it used to be (not counting the PV/PW install price. If grid goes out in winter, the mini-splits go off and we're oil heated which should last a while in case of an extended outage.

Now, the boiler is over 30 years old, and will probably need to be replaced soon. Been trying to figure out what makes sense and not coming up with good solutions. Replacement (more) efficient oil boiler would be ~$12k. Gas boiler is a non-starter due to venting as it would require re-piping. Heat-pump (Rheem) water tank looks promising, but it's nice to have a (mostly) non-electric fallback when grid is out. Hot water solar panels are another possibility, although they would also need something else to further heat the water. So it's looking like replacing the oil boiler with a new one may be the best solution. Any other suggestions?

Have you considered cogen? You use heating oil to run a diesel for power, and the waste heat is used for hot water/heating. They aren't very common outside of the northeast, but with all the oil heat in the northeast, they seem to have found a niche. I have no idea if modern ones are variable speed inverter/grid-tie.

All the best,

BG

 

[skepticcyclist]

I personally am really glad I am neither in PGE or SDGE territory, here in CA. My monthly Natural gas bill for 9 months out of the year is <$30 a month. My Clothes dryer is Natural gas (with no hookup for an electric dryer in my laundry room which I found strange for a home built in 2007 but /shrug).

Nov - Jan when I need to run the heating, its 70-80 a month those months.

Same here. My summer gas bill is often less than $20 with most of that taxes and fees. Winter may get up over $50, but most often under $50

 

[holeydonut]

Same here. My summer gas bill is often less than $20 with most of that taxes and fees. Winter may get up over $50, but most often under $50

Do ya'll like not have women in the house hold who wash their hair and like blow through your 50 gal gas water heater? We're using about 25 therms per month for hot water.

Maybe I need to wrap my hot water heater with that weird heat reflective insulation/padding crap?

 

[jboy210]

Same here. My summer gas bill is often less than $20 with most of that taxes and fees. Winter may get up over $50, but most often under $50

How many therms do you use in the middle of winter? We use about 110 in December, our highest month. Cost about $200.

We use about 14 therms/mo during the summer. Bills about $14/mo in summer.

We are hoping to use less gas this year since we reinsulated the attic and are replacing a drafty second fireplace from the 80s.

 

[charlesj]

Do ya'll like not have women in the house hold who wash their hair and like blow through your 50 gal gas water heater? We're using about 25 therms per month for hot water.

Maybe I need to wrap my hot water heater with that weird heat reflective insulation/padding crap?

Be careful with that wrap. You need an air gap between the heat source, water heater and the foil. Not sure how well it would work on a water heater. Use regular blankets for it.

 

[charlesj]

Used 20 therms this past bill and it costs me $33.34.
Winter time this Jan used 57 therms with radiant floors, super insulated 4000 sq ft house, almost $100.
We have heater off for 7 month.

 

[wwu123]

@wwu123 the other thing not mentioned yet about the recirc pump built into the Navien unit is that it is variable speed. When you first start to use hot water, it fires up the heater and then runs the pump at a high flow rate to push the newly heater water through the pipes as fast as it can. When it senses that the return water is hot enough, it slows down or stops, allowing the just the user flow of hot water to go through the system.

It is important to insulate your hot water pipes, including the return, as much as possible or this will lead to significant energy loss. If I had more time when my house was under construction, I would have gone along all the pipes and filled in the gaps between the closed cell foam pipe insulation with spray foam.

The Navien sounds nice, will have to look into it next time. Can the Navien use the cheat of using the cold water side as a return through? There's no way we can plumb a return all the way from the bathrooms without ripping out all the walls and floors again.

Fortunately or unfortunately, our Noritz is 12-years old and shows no signs of dying anytime soon, even with no maintenance - it's pampered with whole-house filtered and softened water so we don't even do annual cleaning or flush on it. We do have access to wrap all the pipes in the crawlspace, and once they go into the wall cavities, any waste heat would still heat the house the 6. months of the year we're using gas heating anyways.