Natural Gas Furnace Vs. Heat Pump ?

If you live in a cold climate, the heat pump will be inefficient when the temperature drops below freezing, but at moderate temperatures the heat pump will be very effective. I would opt for both so that my backup generator could run a heat source during a power failure.

 

The best time to consider a heat pump in New York is during the design phase, before construction begins, because you really want a ground source system this far north. The newest air source heat pumps claim to work below freezing, but nothing will be as efficient as a ground loop well below the frost line. I am in a similar situation in New Hampshire. We heat with fuel oil, and I have a gasoline generator for power outages. I would love to retrofit a ground source heat pump system, but I won't live long enough to save any money doing it.

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In theory, the heat pump is more efficient because it just MOVES the heat from one area to another and does not create it.

 

The theory says that that is true unless the heat pump is working against a large temperature differential. (sorry, but that's the engineer in me)

JeffD

 

This is not necessarily the case.
Ground Source Heat Pumps are used very efficiently in some very cold climates.
Costs and efficiency depend largely upon the type of soil you are sitting on top of.

Air Source Heat Pumps do loose efficiency as the outside temperature cools.
However, even ASHPs have improved their efficiency and capabilities over the years.

In Minnesota, our GSHP has supplied all our heat for the last 5 winters with no need of our backup heat.

As for the environmental question, since this was posted in the environmental forum, no question the heat pump is better than a gas heater.

 

Simple answer

Ground Loop heat pump is the only answer if all you have is electricity and it is the only valid form of electric heat.

Natural Gas is almost always cheaper for likely another couple decades
As for being cleaner, a decent 98%+ NG heater is almost always less polluting on a CO2 basis than electricity, my state with its 43% efficiency coal fired electricity in many areas makes air to air heat pumps/resistance electric heat a real polluting looser compared to NG.


NG is also available as a heat pump and combined cycle (Japan) which blows away all but solar offerings and wasting solar energy on inefficient heat results in heavy metal Pollution from producing and inevitably disposing of the worn panel.


Air to Air heat pump is just a space heating toy that should have a real backup.
(Unless you want to experience what Texas did)
Air to air is best as AC with use as an occasional space heater in mild weather
Air to air heat pumps have a piss poor trac record on reliability, releasing refrigerants into the environment and being mostly unrecyclable with a very poor track record on accidental release during disposal. NG on the other hand has no refrigerant to spill.

Electric heat unlike electric transportation is a huge waster of power heavy metals and infrastructure and to be honest air to air only heat pump houses should be banned due to the extreme Pollution from having to overbuild infrastructure and the massive supply side heavy metal pollution from creating/supporting the infrastructure wasted on inevitable resistance heating.


Like everything there is a happy medium, either extreme without proper infrastructure is going to damage the environment more.

As a country we need to stop making platitudes and make common sense changes slowly with plans for the disposal of equipment (which we really don’t do today) along with understanding that cradle to grave some technologies have far worse long term consequences if not implemented/used properly.

Right tool for the job situation.

Now if a day comes that we have unlimited thorium power that is too cheap the measure and infrastructure that lasts hundreds of years by all means, waste electricity on resistance power but I don’t think we will get to that point.


What is very unfortunate is that we waste the 60%+ of heat from power plants on heating rivers, in Europe waste heat is transported via hot water pipes to buildings up to 100 miles away, I live under 7 miles from a power complex and our entire area is under 15 from it, if our area was planned correctly we could get “free” distilled hot water to all our homes and make heating more of a non_issue

 

Numerous modern air-source heat pumps can supply their full rated heat output at ambient air temperatures well below freezing, to significantly colder conditions than products of the previous generation. And they don't just quit just below that temperature, but continue producing at reduced output as temperatures drop.

This is one of those specifications that must be included in the selection process. The more detailed spec sheets, not within the usual promotional materials, should also have charts or tables of the heat output vs outside temperature. I used such detailed specs, combined with some daily electrical records taken during a prior severe cold snap, to help select the size of my system, rather than go by the crude guidelines being used by the salescritter. I selected a step smaller than he initially called for, and haven't been disappointed. Though in the next few years I also made several improvement to the building envelope, reducing heat loss and allowing the heat pump to suffice to colder conditions.

The primary downside of ground source is the high cost of installing the ground loop. Small land parcels may also lack enough space for horizontal loops, forcing vertical drilling. For my dad's house, an uninsulated century-old house on a farm east of the coastal mountains where -20F used to be somewhat common (and even -35F just after I moved away, but before climate change nearly abolished those coldest conditions), ground source was the right choice when he became unable to feed the old wood furnace.

For my suburban coastal location, in a house built in the mid-1980s and just barely squeezing in under an obsolete building code before insulation standards increased, a 2009 air source unit works great. The coldest it has seen was +6F, which did require more supplemental heat from the original electric system, but the heat pump still carried the majority of the load. Some colder-climate models existed then, and a lot more exist now. Larger capacity systems can also be selected to deal with the reduced output of the coldest nights.

I must strong disagree with this severe disparagement of air-source heat pumps. My Fujitsu single-zone mini-split has been great, and completely reliable over its 12 years so far. Though I can't say the same for a neighbor's traditional loud single-speed non-inverter heat pump, much younger but requiring emergency service at least every year. At least the other neighbor with a Daiken two-zone mini-split, has a trouble-free experience matching mine.

Note that while natural gas systems don't have any refrigerant to spill at end of life, their supply system is continuously spilling significant quantities of an equally bad gas, methane. And even without any spills, their regular carbon exhaust is significant, exceeding the refrigerant the might get spilled from heat pumps. I'm looking forward to the day when most heat pumps can use R744 as a refrigerant, much more benign that other current refrigerants, so much so that it can simply be vented at end-of-life. (Yes, chemically it is just as bad as CO2, because it is CO2. But as a refrigerant, is it measured in ounces, not tons, so is insignificant.)

When combining new construction with recent cold-climate air-source heat pumps, capacities and insulation levels can be set to do the job to some quite cold conditions, making them competitive against ground source systems in colder climates than would have been considered a decade or two ago. And either path is more environmentally friendly than natural gas.

 

The trouble is most who have the air to air inserts also have a resistance water heater, resistance stove and poor insulation
A house powered this way can use 100’s of times more power than an EV.
which drives a host of unforeseen costs and polluting upstream.
Which is better, a 43% eff coal plant, a 65% max gas plant running a 100% eff resistance heater
or a 98% efficient NG unit?


Air to Air pumps run mostly as resistance heating in this area

(we have 2 solid months every year below 0F)

The use case where they are actually significantly more efficient than resistance is so seldom as to make them useless as heat and honestly where they are most efficient I don’t even run heat (25F+) I can usually leave my heat off as the house stays above 50F

I would never use an Air to Air without an NG backup and view them more as an AC option.
The fact they are cheap compared to a real system is a case of getting what you pay for.

Only use case outside ac is if you live in a Mobile home and can only get resistance heat or a low efficiency propane system, even then having a backup that is not dependent on the electric grid is important.

my guess is my wintertime $12 electric bill and $25 gas bill is likely a fraction of the energy use of most here and is likely a fraction of the CO2 of those nearby with a $450 a month electric bill running efficient air to air heat pumps?

 

I also changed my resistance water heater to a heat pump water heater, getting very considerable energy savings.

Poor insulation is an issue regardless of heat or cooling source. And can be remedied. And is a non-issue in new construction.

My all-electric house uses the energy that would drive a Tesla 3 for 21,000 miles per year. That isn't "100’s of times more power than an EV". And this isn't even new construction that meets modern energy codes, or even mid-1980s energy codes in the nearby then-incorporated areas.

And my rooftop PV system produces all of it, though I still use the local power grid as a time-shifting battery.

For your grid: 65% gas plant running a 290% efficient heat pump (HSPF=10, and better is now available). That puts out twice as much heat as that 98% efficient NG unit.

For my grid: 90% Hydro + wind + solar driving heat pumps.

Sounds like it is time for them to upgrade to systems that work well below 0F. And since OP would be installing a new unit, not a pre-owned twenty year old unit, he doesn't need to stick with just those old crappy units that shut down at freezing or 0F.

 

You seem to be taking the worse case scenario and applying it to anyone that uses an ASHP.
I don’t think that is valid.

 

Listen to the engineer up there. If you have ng then use it. The best implementation is dual fuel, meaning electricity and ng using a heat pump and a ng furnace along with a decent Honeywell thermostat capable of a dual fuel setup.

A heat pump is the same as a standard split ac with a couple of cheap additions. A reversing valve, one additional txv metering device and a defrost board. Ac works as expected, heat for 40f and above from the heat pump, heat below 40f from the ng furnace. No electric strip heat, the furnace operates during a heat pump defrost.

No concern with extreme cold degrading the heat pump output, easy to have a small generator run the furnace in a power fail (impossible with a heat pump using a small generator) and cost effective upfront and in operation. Standard hvac techs can fix it as a plus. No need for expensive drilling required for ground source heat pumps. I would go dual fuel even if I had to use propane although ng is really cost effective both up front (no tank) and in operation.

Forget about minisplits if you have walkin closets, decent baths, utility rooms, lots of bedrooms, etc, eg a normal American house. Minisplits in a decent house cause poor air circulation and uneven temperatures. Minisplits are nearly impossible to use with efficient media filters or uv lights. Minisplits have difficult and messy to clean indoor coils and are largely throwaway if they break especially for the average hvac tech. Minisplits are poor at humidity control. They are relatively cheap and are a logical step up from a window unit. As a result they can be a reasonable bonus room or garage solution. Maybe a fit in a small house with an open floor plan.

American Standard or Trane are good AC or Heat Pumps. Two stage or Full Variable Speed compressors for variable capacity (similar to minisplit's single redeeming feature). A whole house panel mounted surge suppressor is recommended no matter what.

 

attached is the curve of the most common ASHP available, it’s efficiency drops to COP=1 @ right around 0F +\-5F which is identical efficiency to an antique space heater.
The worlds most efficient air to air drops to COP=1.1 at -20F and considering we normally have 2 months around -15F+\-15F that still isn’t good enough in terms of grid loading.
(10-40% over unity is still worse than NG)

in my state over half of a typical homes annual power is used during 2 months of the year and those 2 months average below zero

I think Texas proved my view fully valid, single heat source homes are a bad idea

The cheapest easiest systems typically installed in Texas are even less valid

If you have NG it is best as primary heat for most climates present in the upper half of the country,
ASHP is a neat toy and is great for AC and supplimental but is a poor choice as your only heat source considering the power usually goes out in the worst weather.

 

If there is already a NG line to the rest of the house, use it as back up to the heat pump instead instead of a resistance heater.

You make the heat pump primary, and have the NG take over at an outside temperature you are no longer comfortable with it operating at.

 

First, as this was asked in the environmental forum, I didn't know which took priority, cost or the environment.
Second, air source or ground source was not stated, so prior to the clarification, only considering and talking about ASHP was premature.

Now that both have been clarified, I would second Trollbait's suggestion above. ASHPs to handle the bulk of heating and cooling needs, with nat gas backup (if already running to the house).

One other note, if money is the primary concern, I would suggest this should not be in this sub-forum.

 

I have both a heat pump and a gas furnace. I set my honeywell thermostat to switch over to gas @ 40F. The gas furnace is more efficient. The heat pump heat is much less dry and more comfortable. I like them both. Heat pumps are most efficient when the temps are 45-50F and above outside.

 

Which one?

Down to just +40F? That is seriously old school, 20th Century. Try moving into the 21st Century, where LG rates one of its heat pump product lines by their outputs at 5F.

I'm seeing other information about ducted ASHPs now commonly being sized to carry the full heating load down to +10F, but that threshold is somewhat arbitrarily selected as an economic choice, and they can be sized for lower temperatures.

Mini-splits don't cause that. That is a result of zoned (i.e. no central ducted furnace) systems regardless of fuel source. Many of us have dwellings built that way.

I don't see why anyone should handicap themselves by considering only the "most common" product, not the better cold climate products.

I don't yet have a pointer to world's best, but I'm seeing a big set of LGRED performance tables where the very first datapoint works out to a COP of 1.85 at -13F. Then 2.5 at 0F, 2.85 at 17F. Some other combinations farther down the tables do a bit better.

I'm trying to figure out which part of WI that is. It isn't here, which is colder than the first places I checked in the OP's state of NY:

Heat pumps are rated for average efficiency over the entire heating season. Since no place goes direct from sub-zero or 15F to summer with no shoulder heating seasons in between, judging the environmental value of heat pumps solely by the coldest temperatures of the year, will be misleading.

I do agree here. We kept our original woodstove. Have used it just 3 times since adding the heat pump 12 years ago, but actually needed it only once, during an extended power outage.

Texas seems to want to deny AGW, while simultaneously depending on AGW to banish the severe winter cold snaps that it used to regularly suffer. They want to use it as an excuse for not winterizing anymore.

AGW appears to have reduced both the frequency and typical severity of their severe cold, but not eliminated it. It has had greater effectiveness at erasing their collective memory of how severe the cold can get there.

 

You could benefit from a modern heat pump.

And maybe some insulation and air infiltration improvements. At 50F outdoors, my house doesn't need any heat indoors. Unintentional heat from other sources, plus diurnal solar heat gain, don't flow out fast enough to need intentional heating turned on.