HVAC replacement - looking for advice from those who have BTDT

[Anonymous]

I have a 13 year old gas furnace that needs replacing. I've got a company coming out for a quote, and will get multiple quotes. But I've never replaced a furnace, so I am looking for advice from those who have on what you learned, what you wish you had known, wish you had done differently etc. Thoughts on gas furnace vs. heat pump, replacing just the furnace vs. the furnace and the AC, etc.? Any other advice? Small 1951 house in nova.

[Anonymous]

If you want to do a heat pump do dual fuel (gas furnace plus heat pump). The heat pump will be more efficient than the furnace but it runs on electricity which is more expensive than natural gas. Also, it is hard to properly size a heat pump for our climate because the heating loads are larger than the cooling loads so if you size the heat pump for heating it will be oversized for cooling and cause humidity issues in the summer and won't be as efficient. It makes more sense to supplement with gas for heating (plus that is less difficult to install than a full heat pump conversion).

If you get a good heat pump you could be eligible for a $2k federal tax credit. Overall I think heat pumps are worth it if you use oil/propane heat because it will save you money on utilities. If you already have gas, it does offer the flexibility of toggling between electricity and gas in the winter, and the heat is less drying. But you probably won't save money especially if a basic furnace /ac works well for your home.

[Anonymous]

I would get a second opinion about replacing the furnace. About 5 years ago, I had one company swear that I needed a new natural gas furnace when my fan motor died, and another company just replaced the fan motor.

I just replaced my whole HVAC system (furnace and AC) because my AC compressor died and the replacement costs were prohibitive because my old AC used the older freon. I went ahead and replaced both AC and furnace (rather than just the AC) because my furnace was 20 years old, there was significant costs saving for replacing both (like 10K for replacing both AC and furnace and 6K for replacing either AC or Furnace) due to labor savings. I will also get 2 $600 tax credits for AC and furnace (1200 total). Keep in mind that if you get a new AC, it will need to have a minimum efficiency (like 16 SEER) to qualify for the tax credit. I got wildly different estimates for installation with the identical furnace/AC units - I think parts are in short supply and every installer buys from the same warehouse.

When replacing the HVAC, I asked about a heat pump and was told the cost would be about $15K because it would require electrical and duct work. I kind of wish I did it anyways because I would like to install solar power and that heat pump could be run without further gas costs. As a prior post mentions, there is a 2K tax credit for heat pumps.

[Anonymous]

We replaced both furnace and ac when the ac conked out after 20 years (leaking freon). The contractor said it is a little cheaper to do both at the same time and offers more options. We got a variable stage communicating system which is a little pricier, but our old system wasn't heating or cooling our townhouse evenly and the variable stage helps with that. If your current system works well and you just want to do a straight replacement, whether you do both at the same time depends on how old your AC is. If you think the AC will last a while longer then don't replace it yet. If I recall correctly the AC is more expensive than the furnace.

[Anonymous]

Anonymous wrote:If you want to do a heat pump do dual fuel (gas furnace plus heat pump). The heat pump will be more efficient than the furnace but it runs on electricity which is more expensive than natural gas. Also, it is hard to properly size a heat pump for our climate because the heating loads are larger than the cooling loads so if you size the heat pump for heating it will be oversized for cooling and cause humidity issues in the summer and won't be as efficient. It makes more sense to supplement with gas for heating (plus that is less difficult to install than a full heat pump conversion).

If you get a good heat pump you could be eligible for a $2k federal tax credit. Overall I think heat pumps are worth it if you use oil/propane heat because it will save you money on utilities. If you already have gas, it does offer the flexibility of toggling between electricity and gas in the winter, and the heat is less drying. But you probably won't save money especially if a basic furnace /ac works well for your home.

No need to do a dual system in this region or really anywhere else - really not sure what the PP is talking about.

We have a pretty mild climate in this area in the winter, especially the last few years when we've barely had any extended stretches where the temps have stayed below freezing.

Heat pumps become less efficient the colder it gets but they still work just fine even in colder temps but they are particularly efficient in colder temps above freezing which is mostly what we have around here.

And the relative load language in the previous post makes no sense at all - I don't think it is even true but if it were the greater relative load in our local climate would be in the summer where it in fact can be miserably hot - it really is very rarely cold in this region.

FWIW we've had a heat pump for four years and it works great - it is hard to tell because there are a lot of variables (gas prices in DC vary year to year) but thus far it appears that our electric has gone up a bit more than our gas has gone done.

Which is worth it because if we are going to solve our global warming challenge we are going to have to stop using gas asap - we have shed 3 of the 5 things in our life that run on gas and are getting rid of the 4th in January and we get about 80% of the electricity that runs those replacements from our solar panels.

[Anonymous]

Anonymous wrote:

Anonymous wrote:If you want to do a heat pump do dual fuel (gas furnace plus heat pump). The heat pump will be more efficient than the furnace but it runs on electricity which is more expensive than natural gas. Also, it is hard to properly size a heat pump for our climate because the heating loads are larger than the cooling loads so if you size the heat pump for heating it will be oversized for cooling and cause humidity issues in the summer and won't be as efficient. It makes more sense to supplement with gas for heating (plus that is less difficult to install than a full heat pump conversion).

If you get a good heat pump you could be eligible for a $2k federal tax credit. Overall I think heat pumps are worth it if you use oil/propane heat because it will save you money on utilities. If you already have gas, it does offer the flexibility of toggling between electricity and gas in the winter, and the heat is less drying. But you probably won't save money especially if a basic furnace /ac works well for your home.

No need to do a dual system in this region or really anywhere else - really not sure what the PP is talking about.

We have a pretty mild climate in this area in the winter, especially the last few years when we've barely had any extended stretches where the temps have stayed below freezing.

Heat pumps become less efficient the colder it gets but they still work just fine even in colder temps but they are particularly efficient in colder temps above freezing which is mostly what we have around here.

And the relative load language in the previous post makes no sense at all - I don't think it is even true but if it were the greater relative load in our local climate would be in the summer where it in fact can be miserably hot - it really is very rarely cold in this region.

FWIW we've had a heat pump for four years and it works great - it is hard to tell because there are a lot of variables (gas prices in DC vary year to year) but thus far it appears that our electric has gone up a bit more than our gas has gone done.

Which is worth it because if we are going to solve our global warming challenge we are going to have to stop using gas asap - we have shed 3 of the 5 things in our life that run on gas and are getting rid of the 4th in January and we get about 80% of the electricity that runs those replacements from our solar panels.

Heat pumps work fine in our climate. I didn't say that they don't. But you do have to size them correctly to heat enough in the winter, which means oversizing them for the summer. That is not optimal for comfort or efficiency in the summer.

The reason cooling loads are less than heating loads even though 90+ degree temps are hot, they are only 20-30 degrees hotter than 70 degrees which is what most people find to be comfortable. On the other hand in the winter it is not uncommon to get down to 20 degrees which is 50 degrees colder than 70 degrees.

Many people don't have natural gas hookups and heat pumps are a great option since it will be more cost effective than oil or propane.

But if you already have natural gas, dual fuel is the best option for balancing reducing emissions, comfort and cost.

[Anonymous]

OP here, this is great, thank you!

[Anonymous]

We had a heat pump in our older house with an electric furnace. It could not handle the winter, the furnace had to kick in on days that it got really cold. Our new house as duel fuel gas+heat pump and seems to work better. Ironically we have doubled the size of our home but our gas+electric bill is only about $20 more expensive than our electric bill at our old place. So PP is correct in that gas is definitely cheaper.

[Anonymous]

I second the comment about variable stage (or multi-stage, or modulating). In my experience a modulating gas furnace and two-stage air conditioner made a big difference in comfort. Presumably heat pumps are available with similar. It eliminates the mentioned concerns about the system being oversized for some seasons, because it changes its capacity as needed.

[Anonymous]

Anonymous wrote:I second the comment about variable stage (or multi-stage, or modulating). In my experience a modulating gas furnace and two-stage air conditioner made a big difference in comfort. Presumably heat pumps are available with similar. It eliminates the mentioned concerns about the system being oversized for some seasons, because it changes its capacity as needed.

I am not sure if this is true. My understanding is you lose the efficiency of the variable stage in the summer when it is oversized. Since it is oversized it can't run at the low level.that you actually need so it will shut on and off like a single stage. In addition to costing you more in electricity bills it won't do as good s job removing humidity.

[Anonymous]

Anonymous wrote:

Anonymous wrote:I second the comment about variable stage (or multi-stage, or modulating). In my experience a modulating gas furnace and two-stage air conditioner made a big difference in comfort. Presumably heat pumps are available with similar. It eliminates the mentioned concerns about the system being oversized for some seasons, because it changes its capacity as needed.

I am not sure if this is true. My understanding is you lose the efficiency of the variable stage in the summer when it is oversized. Since it is oversized it can't run at the low level.that you actually need so it will shut on and off like a single stage. In addition to costing you more in electricity bills it won't do as good s job removing humidity.

I didn't mean to imply that proper system sizing doesn't matter. I meant that caveats about heat pump capacity in summer vs. winter aren't relevant, because the system has more ability to adapt itself to conditions.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:I second the comment about variable stage (or multi-stage, or modulating). In my experience a modulating gas furnace and two-stage air conditioner made a big difference in comfort. Presumably heat pumps are available with similar. It eliminates the mentioned concerns about the system being oversized for some seasons, because it changes its capacity as needed.

I am not sure if this is true. My understanding is you lose the efficiency of the variable stage in the summer when it is oversized. Since it is oversized it can't run at the low level.that you actually need so it will shut on and off like a single stage. In addition to costing you more in electricity bills it won't do as good s job removing humidity.

I didn't mean to imply that proper system sizing doesn't matter. I meant that caveats about heat pump capacity in summer vs. winter aren't relevant, because the system has more ability to adapt itself to conditions.

I'm sorry, I'm not following. You are saying it's "not relevant" if a variable stage system is properly sued for heating but oversized for cooling? Why not? You are paying so much for the variable stage but o let getting the benefits in the winter.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:I second the comment about variable stage (or multi-stage, or modulating). In my experience a modulating gas furnace and two-stage air conditioner made a big difference in comfort. Presumably heat pumps are available with similar. It eliminates the mentioned concerns about the system being oversized for some seasons, because it changes its capacity as needed.

I am not sure if this is true. My understanding is you lose the efficiency of the variable stage in the summer when it is oversized. Since it is oversized it can't run at the low level.that you actually need so it will shut on and off like a single stage. In addition to costing you more in electricity bills it won't do as good s job removing humidity.

I didn't mean to imply that proper system sizing doesn't matter. I meant that caveats about heat pump capacity in summer vs. winter aren't relevant, because the system has more ability to adapt itself to conditions.

I'm sorry, I'm not following. You are saying it's "not relevant" if a variable stage system is properly sued for heating but oversized for cooling? Why not? You are paying so much for the variable stage but o let getting the benefits in the winter.

If I understand what you’re saying, I guess the solution is a heat pump with more than 2 stages, or an inverter heat pump which is in effect infinitely variable.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:I second the comment about variable stage (or multi-stage, or modulating). In my experience a modulating gas furnace and two-stage air conditioner made a big difference in comfort. Presumably heat pumps are available with similar. It eliminates the mentioned concerns about the system being oversized for some seasons, because it changes its capacity as needed.

I am not sure if this is true. My understanding is you lose the efficiency of the variable stage in the summer when it is oversized. Since it is oversized it can't run at the low level.that you actually need so it will shut on and off like a single stage. In addition to costing you more in electricity bills it won't do as good s job removing humidity.

I didn't mean to imply that proper system sizing doesn't matter. I meant that caveats about heat pump capacity in summer vs. winter aren't relevant, because the system has more ability to adapt itself to conditions.

I'm sorry, I'm not following. You are saying it's "not relevant" if a variable stage system is properly sued for heating but oversized for cooling? Why not? You are paying so much for the variable stage but o let getting the benefits in the winter.

If I understand what you’re saying, I guess the solution is a heat pump with more than 2 stages, or an inverter heat pump which is in effect infinitely variable.

You are assuming that an inverter heat pump's capacity can go all the way down to zero, and that's not accurate.

https://www.linkedin.com/posts/allisonabailes_can-you-oversize-a-mini-split-heat-pump-activity-7105132985556889600-d5Ss?utm_source=share&utm_medium=member_desktop

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:I second the comment about variable stage (or multi-stage, or modulating). In my experience a modulating gas furnace and two-stage air conditioner made a big difference in comfort. Presumably heat pumps are available with similar. It eliminates the mentioned concerns about the system being oversized for some seasons, because it changes its capacity as needed.

I am not sure if this is true. My understanding is you lose the efficiency of the variable stage in the summer when it is oversized. Since it is oversized it can't run at the low level.that you actually need so it will shut on and off like a single stage. In addition to costing you more in electricity bills it won't do as good s job removing humidity.

I didn't mean to imply that proper system sizing doesn't matter. I meant that caveats about heat pump capacity in summer vs. winter aren't relevant, because the system has more ability to adapt itself to conditions.

I'm sorry, I'm not following. You are saying it's "not relevant" if a variable stage system is properly sued for heating but oversized for cooling? Why not? You are paying so much for the variable stage but o let getting the benefits in the winter.

If I understand what you’re saying, I guess the solution is a heat pump with more than 2 stages, or an inverter heat pump which is in effect infinitely variable.

You are assuming that an inverter heat pump's capacity can go all the way down to zero, and that's not accurate.

https://www.linkedin.com/posts/allisonabailes_can-you-oversize-a-mini-split-heat-pump-activity-7105132985556889600-d5Ss?utm_source=share&utm_medium=member_desktop

On the 2-stage A/C I had in my previous home, 1st stage capacity was 2/3 of 2nd stage. So if a unit was oversized, but could go down to 30% of full capacity, then it could have a 1st stage with a ratio similar to my A/C's. If you're mainly concerned with heat pump overcapacity during heating season, then the BTU output of the stages of a 2-stage gas furnace would be more relevant. I don't know what that is, because I had a modulating gas furnace.