HVAC in New Construction in 2024

Kaos · October 13

https://forum.heatinghelp.com/discussion/comment/1867512#Comment_1867512

The blower on the burner is about 100W. Fuel pump is 10-20W. Zone valves also use power (some less then others). ECM pump when pushing pressure will also use more. Most around me that I have seen have 3-5 non-ecm pumps. Adding it all up, 200W is on the low side. Running a boiler uses real power, ask anyone off-gird.

Nameplate efficiency in the field of any boiler is highly optimistic and assuming 2cop for heat pump is on the bottom end. Even with those assumption the operating cost is close enough not to matter. Get a decent equipment and decent install with a ASHP and you are still ahead even with expensive power.

Once you need AC, the maintaince cost is about the same as a heat pump. A heat pump is actually less usually as it is much easier on parts since it is inverter controlled and there are no hard starts. With dual fuel now you still have the extra maintaince of the boiler plus the cost of buy/install. No matter how you cut it, the maintaince will be higher for any duel fuel setup.

@mattmich I have built that exact setup for my home. Beside the 3x install cost, it feels like it should work well but doesn't in the real world. PM me if you want details.

https://forum.heatinghelp.com/discussion/comment/1867515#Comment_1867515

In any place that needs AC (which is now the cases even in great white north up here), hydronics is dead as you have to install two complete separate systems to get AC. Any older residential hydronics around me is getting pulled out in most large renovations. It does not exist at all in new builds except for snow melt. The only place hydronics will stay is in the commercial world.

Hot_water_fan · October 13

@Kaos this is cost vs. value. If someone wants to pay for hydronics, then it'll be installed. It becomes a luxury product - to be fair that's like most everything else in a house. In the world where hydronics is a luxury good, then the industry especially needs to become customer focused.

Roger · October 13

Removing a boiler or furnace without living though a typical winter with a heat pump and without review of forward looking electric rates is malpractice. And saving $1,000 per year adds up over the life of the boiler…and that's not adjusting for electric rates that are increasing at 15% to 25% per year in New England.

@Kaos , an oil burner is ON/OFF, so if the boiler is fired at 0.85 GPH for 700 gallons, that's 825 hours or about $50 per year in electricity at $0.30/kWh ($12/gallon equivalent per unit of energy, see above). The 2.1 COP (210% efficiency) is a seasonal COP from the Department of Energy Study for cold climate heat pumps selected for their top performance, and the 87% likewise reflects top performing oil boilers (top performing gas boilers may be slightly higher). Since that is an annual/seasonal COP, the COP is actually substantially lower in the cold of winter, making the heat pump option unaffordable compared to oil ($3.50/gal).

The Vermont Department of Public Service has warned the Public Utility Commission that cold climate heat pumps don’t always lower heating bills. Their analysis shows results depend on electric rates, and Vermont has the lowest electric rates in New England (where rates can be 30%+ higher).

Kaos · October 13

I took a quick look at the DOE study. Almost all the units were undersized (HP bellow Man J):

No $%& efficiency is going to suck when you need to run aux heat.

Around me code requires the heat pump to meet design load without Aux heat for new build, seasonal efficiency will be much higher.

Roger · October 13

@Kaos , it’s an interesting theory, but per the study: “Most of the all-electric sites had very few hours with outdoor temperatures below the compressor lockout temperature.” This is the maximum outdoor temperature at which the auxiliary heat source operates, so it will not run unless it’s very cold out. The auxiliary heater ran 4.8% of the time on average at these sites.

“Additionally, all the sites were in dry climate zones where the need to defrost the outdoor coil would be much less than that of heat pumps installed in humid or marine climate zones.” We could expect the efficiency to be worse on the east coast, especially near the Atlantic or where it is more humid in the summer.

mattmich · October 13

» it will not run unless it’s very cold out. The auxiliary heater ran 4.8% of the time on average at these sites.

That's 420 hours or 18 days of super cold where we're using resistive electric heating.
I would not consider that an endorsement, especially in light of the "3 of 8 pizza slices" efficiency from earlier in the thread.

As more homes get built that way, this will stress the grid like a heat wave does in the South.

Roger · October 13

Thank you, @mattmich - I should have been more clear as that is actually 4.8% of the time the systems were monitored during the study, not of the entire year, but still about 200 hours in a heating season. The vast majority of the energy consumption is from the compressor.

To your point about stressing the grid, adding heat pumps will need to triple the size of the residential grid power supply in cold climates, and adding electric vehicles for each home will move it to 4X - that's a lot of pizza. Some states like Maine have electric grids that are already "winter peaking", using more electricity in winter than summer.

Kaos · October 14

@Roger Can you post the section with the seasonal COP of 2.1

Most of the stuff I quickly read said efficiency as expected based on manufacturer data. For most this means COP around 2 at 5F, not seasonal COP of 2.

I'm still having a hard time believing hitting rated efficiency of a 3x oversized boiler under real world conditions. Something to back that up.

Depending on residential heat pump penetration, Ontario's power grid peak would have to increase by 5 to 20%, I doubt yours would need to increase by 2x or 3x. Around me the utility offers special TOU pricing which pushes most EV charging off peak hours so they don't really effect the grid.

Re Undersized heat pump, they were definitely undersized:

Heat pumps pick up efficiency at partial load, so an undersized unit gets a double whammy of efficiency hit. You need more aux to meet peak load plus it runs at higher percent of max the rest of the time, thus lower COP.

This is still a moot discussion as nobody will install an boiler in a new build. It will be either furnace with AC/heat pump or heat pump only.

Hot_water_fan · October 14

This is still a moot discussion as nobody will install an boiler in a new build. It will be either furnace with AC/heat pump or heat pump only.

this seems drastic :). A few percent will!

jimmylym · October 14

The numbers on “forced air” don’t really add up if they’re excluding heat pumps, since most still use air distribution. The drop from 71% to 50% seems more like a categorization issue than a real market shift. I’ve noticed the same thing here — rising electric rates are definitely changing the math on heat pump efficiency. In areas without natural gas, like parts of PA, the decision between propane, dual-fuel, or all-electric is getting trickier. And totally agree about radiant — in newer, tight homes with lower heat loads, the benefits don’t justify the cost anymore. A well-designed variable-speed forced air system really can be just as comfortable and far easier to maintain. Also, proper airflow maintenance makes a big difference — even something as simple as routine airduct cleaning (we deal with that a lot in Boise) can improve performance and system longevity.

Roger · October 14

@Kaos , it's interesting that you are focusing on new construction (about 0.5% of homes were added per year in New England since 2017, so it will take 200 years to build up to today's inventory of homes). If a heat pump lasts 12 years, that means 8.3% of heat pumps will be replaced each year on average - this dwarfs the new home applications. Similarly, if a typical boiler lasts 30 years, 3.3% are replaced each year.

A hybrid system with a boiler or furnace for heat will extend the life of the heat pump (as it will mostly be used for air conditioning), saving operational and replacement costs.

Heat pumps are rapidly becoming unaffordable in New England; boilers and furnaces are comfortable and affordable - especially when comparing winter heating. Massachusetts may break the $0.40/kWh barrier this winter as some areas are already at $0.38/kWh. This is about $16/gal of oil and $11/therm of natural gas equivalent on a per unit of energy basis, which is 4.5X to 5.5X the price of today's oil and gas.

The 2.1 COP is the average system heating results in the study - I'm sure you saw the below chart and the supporting data in Table 11. Even a quick glance shows the average is not the 3.0 COP you claim. Sometimes I feel like you are just trying to troll me…

Top performing heat and hot water boilers are low mass with thermal purge, and achieve 97% of rated efficiency. The chimney vented System 2000 Frontier design achieved 85.3% annual efficiency (87.5 AFUE) in this Department of Energy Lab study. Since the study was published, the polypropylene non-condensing Resolute was introduced with 88% annual efficiency (up to 91.1 AFUE), and the Accel CS modulating condensing boiler is a bit higher (up to 96.7 AFUE), but peak efficiency is limited by connected radiation to squeeze a bit more out of condensing during heating.

The Residential Grid would need to provide 3.5X power for full electrification: Per prior posts 11,723 kWh/home is required a typical heat pump application, the US Energy Information Agency shows 601 kWh/home per month average in New England (7212 kWh/year), and there are 2.9 trillion miles driven by light duty vehicles per year and 148 million homes, so about 20,000 miles per home driven; EVs typically get 3 to 3.6 miles/kWh, so that is about 6,000 kWh/home annually. This totals about 25,000 kWh/year which means the residential grid would need to expand by 3.5X. There are approximately 8% average line losses for New England, although line losses are an I²R issue, with losses proportional to the square of the current flow rate, so the incremental loss for increased grid loads during peak periods from electrification (EVs and heat pumps) will typically be in the mid-teen percentage range. Of interest, the increased line losses per home add up to about 1/3 of the total electric consumption of today's homes.

Hot_water_fan · October 14

@Roger don’t forget about new electricity rates for heat pumps. In MA in particular, electricity rates have decreased, not increased. Still pricey! I like my $.15/kwh.

Also - increases in kWh per year don’t map 1:1 to “residential grid would need to expand by 3.5X. ” That’s just a fundamentally flawed conclusion here. That’s assuming that the grid is currently fully utilized, which it obviously isn’t anywhere close to being. Not sure what residential grid means in this context either. With your preferred hybrid setup, the kwhs used could very well increase with the peak winter load remaining the exact same. I like that plan by the way.

Roger · October 14

Thank you, @Hot_water_fan - I'm glad you like hybrid systems with a boiler or furnace to offer a smarter, more flexible solution. There's really no other way to go in an environment with high and ever increasing electric rates. I have seen states and utilities have had to cut rates in an effort to make heat pumps more affordable, as you mentioned. This of course shifts costs to other rate payers and cannot go on indefinitely if heat pump installations garner a larger share of power from the grid. I used the term residential grid as there are commercial and industrial loads that are independent, but the electrical energy served to an electrified residence will need to expand by 3.5X vs a typical home today. For a state like Maine with 750,000 homes, the grid would need to be able to handle the equivalent of about 2,600,000 homes worth of electricity if fully electrified under this scenario.

Hot_water_fan · October 14

@Roger it doesn’t necessarily shift costs to other ratepayers though. It’s the same overall $. A non-heat pump user could pay the same as before. Or they could pay less if the additional kWh at a cheaper rate exceed the before state. We don't have to speculate - across 1500+ utilities, the EIA shows that residential rates are lower as annual consumption/account increases (Table 6 here: https://www.eia.gov/electricity/sales_revenue_price/)

Annual kwh per customer	Average Price (cents/kWh)	Utilities
3,000	$ 28.62	5
4,000	$ 21.71	17
5,000	$ 22.62	43
6,000	$ 18.83	80
7,000	$ 17.16	115
8,000	$ 15.71	108
9,000	$ 14.77	111
10,000	$ 13.85	133
11,000	$ 13.51	146
12,000	$ 13.46	175
13,000	$ 13.39	206
14,000	$ 12.82	170
15,000	$ 12.36	83
16,000	$ 12.16	37
17,000	$ 11.65	22
18,000	$ 12.36	13
19,000	$ 10.77	7
20,000	$ 13.00	37

And this just doesn’t add up. Do you mean annual demand will go up 3.5x? That would make more sense. That’s not the same as the grid must grow 3.5x. That’s not a sensible relationship using the common definition of grid.

Roger · October 14

@Hot_water_fan , many electrification focused states are leading the country with the highest prices of residential electricity, and the constrained gas supply for the New England grid is a contributor to continued escalation. Successful electrification at scale will drive ever increasing demand, and I think it's fair to say that adding the equivalent of almost 2 million homes in Maine will require the grid to expand. To your point, it is likely not 1:1 - it could be higher with AI demand, or lower without AI and with hybrid intervention.

Hot_water_fan · October 14

@Roger I think "many electrification focused states are leading the country with the highest prices of residential electricity" ignores the states actually leading, in electricity's market share of heating, and focuses on rhetoric. Plenty of states south of New England are electrifying heating mostly organically (and have long since adopted AC) without the doomsday predictions coming true. Our electricity is cheap here! Do you all not want cheap electricity up there? The wires to our homes cost the same to install and maintain whether we use 5 MWh or 15 MWh annually. That's where our rates are low in the Mid Atlantic and where the NE rates are not.

The NE gas prices is an interesting point. To me, it points to a good economic case to use less gas. That could be hybrid with gas or even hybrid with oil. It's a bit harder to justify the oil though - even if heating costs are similar, gas has other benefits customers seem to care about. I certainly appreciate the oil case for being able to disconnect from the gas grid for several reasons.

Roger · October 14

New England and mid-Atlantic are experiencing unprecedented electric rate escalations. It's not rhetoric when New York's residential electric rates climbed 50% since 2020 and only 4% in the prior 7 years. New England is out pacing New York, and New Jersey seems to be working hard to catch up with 17% to 20% increases year to date. Our electricity is not cheap here! There are many contributing reasons why rates are so high and continue to climb, but I will leave that for others to research.

Kaos · October 16

Grid capacity (transmission and generation) are driven by peak power. Using more energy generally does not add to grid load. For example, my use energy use with heat pumps increased, but my grid connection and peak demand is the same.

If you are looking for real grid demand increase, look at AI and data centers.

One interesting tidbit is with more electricity use my effective rate ($/kwh) actually went down by about 20% since most of the usage is off peak.

@Roger I took a quick look at that DOE study I'm guessing in the boiler is #3. Here is the part load numbers for the unit:

Which is pretty good, most likely you will see about low/mid 80s efficiency in the real world assuming 2x to 3x oversize.

The heat pump graph you pulled shows exactly what I was talking about. The data clearly shows the energy use from aux drops the seasonal COP down. These units won't lock out till like -30F in most cases but will need to use aux heat (that is heat pump plus aux at the same time) if the heat pump is undersized.

The efficiency of most systems (some outliers for sure) is about 3 COP if you take out aux heat (blue bars). Some sites didn't have aux heat (ie #3) and is close to 3. The text even say that most units hit their HSPF2 efficiency in the field (HSPF2 of 10 is about seasonal COP of 3).

If you re-run your fuel cost with 82% boiler and 3 COP HP, the cost difference will be noise. If power cost go up, with a heat pump you can always add PV to offset cost but you can't make oil (or at least not easily) at home.

Add in one yearly service call to your oil boiler, and you are in the negative.

Now if you are in a place with expensive power, you definitely want to make sure the system is sized right and installed properly to get near that nameplate HSPF2 number.

The title of this post is "HVAC in New Construction in 2024" thus my reference to new build. Retrofit has its challenges as you are dealing with unknown loads and existing house infrastructure. There, a hybrid setup does make sense but I would size heat pumps to handle the full load of the place in case the fuel burner ever fails.

@Hot_water_fan "this seems drastic :). A few percent will!"

You can't do snow melt with a heat pump (or at least a reasonable sized one), these will always have a boiler. If installing the boiler for snow melt, might as well tack some floor heat on there. Any new build that is installing snow melt, BOM and operating cost is irrelevant anyway.

Hot_water_fan · October 16

@Kaos agreed. Hydronics in a new build is a luxury product. People put luxury products into their houses all of the time. Operating costs and install costs are largely irrelevant!

@Roger NJ prices are around 18-20 cents per kWh? That beats oil pretty handily yes? I’m not sure what gas prices are up there.

Roger · October 16

@Kaos , tripling or quadrupling demand will have an outsized impact - "when heat pump loads push up grid loads and costs, power plants win big while all ratepayers end up paying more, which is reflected in the 'energy supply' component of a consumer’s electricity bill." Article and graph. A 10% increase in electrified homes drives a respective 30% increase in demand. Full electrification will drive a 3X to 4X increase in residential demand, which is more than a bit intimidating to contemplate.

The heat pump chart you are referencing shows the impact of auxiliary heat, defrost cycle losses and more in the red bars which results in an average 2.1 COP annually; the blue bars are not inclusive of the full analysis and should not be used to present an artificially high performance level. Although the blue bars should not be used, the average is 2.5 COP, and at a glance you can tell it is not the 3 COP you posted (still trying to troll me?). In addition to comfort, the expense of winter heating is a primary reason why there is a 60% to 80% heat pump drop out rate.

The low mass, thermal purge 87.5 AFUE boiler referenced has an 85.3% annual heat and hot water efficiency with an oversizing factor of 3, not the 82% you posted (see table 3).

I agree with you that all HVAC systems should be sized properly, although this should not be limited to areas with "expensive power".

@Hot_water_fan , NJ prices jumped in July, so now the residential state average is close to $0.24/kWh, which compares to $9.60/gallon of oil ($4.60 at a COP of 2.1) vs about $3.50/gallon for oil. A further 20% increase in electricity rates is expected for next year.

Hot_water_fan · October 16

@Roger I appreciate the load vs. wholesale chart. But why are we assuming no generation will be added? That's what the chart implies. If other states can support high kwh/capita with low rates, what's so special about other states that they cannot?

Roger · October 16

Thank you, @Hot_water_fan - the link has many of the details you request, many of which speak to electrification price increases in the Northeast (the article is pre-AI). I would hope that every effort is being made to keep energy affordable.

Hot_water_fan · October 16

@Roger the article was pretty sparse on details in my opinion. It was missing:

Distribution cost impacts. Is NE special when increased kwh/capita decreases these costs everywhere else in the country?
We agree hybrid is a good solution. Why wasn't that discussed in the article? That'd eliminate the peak load increases entirely yeah?
Still unanswered is why NE cannot add new generation.

Roger · October 16

@Hot_water_fan , I'll let others research and speak to your questions. For your reading pleasure, here is an article Investor-owned utilities could spend $1.1T between 2025 and 2029: EEI . It's important to realize the rapid electric rate escalations in New England, New York, New Jersey all happened before AI data centers became a focus.

HVAC in New Construction in 2024

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