Which is better heat pump or a hybrid heat pump

John732

Just possing a thought. What do you guys think is better and standard heat pump with heat strip or hybrid system which is a heat pump with a fossil fuel source for back up heat. Now going back in time I would say hands down the hybrid system would be more efficient and effective as it gets colder but with all this newer technology these heat pumps go down in lower temperatures now without loss of capacity so now I’m debating the thought of a hybrid. Most people down south it’s a no brained standard heat pump is fine, but I poss this question more gear to the northern climate where we need a back up source. Also another thought we have more solar in hours to which lowers cost of electric. What are your guys comments I’d like to hear professional in put. 

Hot_water_fan

There’s no right answer, pros and cons to both. 

Hybrid: backup source if the heat pump breaks, you can possibly game electricity rates if your utility offers time of use, could avoid future demand charges or save during demand response, you can use a lower end heat pump, and usually non-cold climate heat pumps are more efficient in warmer temps

heat pump only: this could be a cold climate heat pump without electric resistance strips, or could include them. No extra system, no gas service fees, no oil/propane tank to leak, no chimney to worry about, will usually be more appropriately sized then a furnace

hot_rod

A hybrid system with a lp or NG backup would be easier to run off a generator if power outages are of any concern. If the home already has fuel gas on site, or already has a boiler, then the hybrid would be my choice.

With off peak rates and a generously sized buffer you could leverage off peak rates.

As far as water heating, an 80 gallon tank heated to 140 on off peak rates, mix valve it to 115f may work out well for low DHW costs. Some utilities drop down to $.03 per kWh durning nighttime hours.

Jamie Hall

Too many variables. Which might be better in any given application depends, among a host of other things, on what the client's objective in choosing a heat pump (hybrid or straight) is in the first place, electricty or other fuel costs in the area, climate in the area, client's tolerance to no heat/low heat situations, etc.

Even the first one -- objective -- is murky, as the preferred choice should take into account whether the objective is visible green, actual green (which is very different in most of the country), compliance with a mandate (which is no choice at all actually), or just being comfortable at a reasonable price.

hot_rod

This webinar takes you through the hybrid number crunching, piping and control options, 90 minutes.

Areas of Maine put power on sale on weekends .0637, and off peak.132/kwh. Might be hard to make PV pencil out if you can buy electricity that inexpensively?


https://www.youtube.com/watch?v=boqkZD9f7bc&list=PLuuV0ELkYb5VE0I4evUZ30b5U78CRlRdg&index=2

Hot_water_fan

The generator point is a great one: works a bit better with a boiler than a furnace since pumps can be more efficient than blowers, but depends on the install. Not many utilities are here yet, but there’s a future where perhaps hybrids are the go-to option and utilities control, or heavily incentivize, the backup heat to run at certain times. This is common for AC now: my utility has 1 program that cycles the AC some afternoons for $$ and another program that is voluntary for $. It’s been working for years.

This could lead to extremely cheap electricity, as average electricity demand could increase significantly while peak demand could remain mostly flat, thereby spreading distribution costs widely. In my situation, I’ve increased my annual kwh substantially yet peak winter heating demand for me is only 2.5-3kw. That’s nothing. 

Jamie Hall

As I say -- too many variables. Each situation is unique, and has to be analysed on its own.

Hot_water_fan

@Jamie Hall ha don’t you think most Americans have better things to do? I think it’ll just be whatever the contractor or builder decides. 

Jamie Hall

Hot_water_fan said:

@Jamie Hall ha don’t you think most Americans have better things to do? I think it’ll just be whatever the contractor or builder decides. 

Which is why I think it is the responsibility of the contractor or the builder to do this. I don't think the average homeowner wants to -- or is qualified -- to make the necessary comparisons, and the politicians certainly aren't. Some contractors are well qualified to do this -- many of the folks here on the Wall, for instance. Unhappily, even more are one trick ponies, and will sell you what they have whether it will work well for you -- or even work at all. The homeowners often don't help -- the tendency is to go for the lowest price, or quickest install. In their defence, they often don't know any better.

WMno57

If you have a private well, you may want a backup generator. Either propane or natural gas are nice with a permanently installed generator. At that point, you might as well have a natural gas or propane furnace. If you want a heat pump too, why not.
If you are on city water, then electrical outages are less of an inconvenience. And electrical outages tend to be shorter in cities. You could probably get by with a heat pump and heat strips. You would save the monthly charge of gas service, or unsightly propane tank.
How cold does it get in your location?

WMno57

Hot_water_fan said:

The generator point is a great one: works a bit better with a boiler than a furnace since pumps can be more efficient than blowers, but depends on the install.

Any 6 horsepower (3000 watt) or greater generator could easily handle either a furnace or boiler. Most generators below 2000 watts are junk and not worth the trouble.
Sizing generators is important. Too big, and you spend too much and use too much fuel. Too small, and you destroy sensitive electrical equipment.

errorcode

Heat transfere from a heat pump is the refrigerant, a properly sized system with wall mount indoor heads using a quality cold climate product will work fine in most all cases. When we install heat pump ducted systems the dynamic changes, the heat transfere is no longer coming off the coil directly heating the space, it now has to over come velocity loss and heat loss from the ductwork in an unconditioned attic, basement, or crawlspace. A good percentage of homeowners don't want to see a head on the wall, and may even have existing ductwork. 
In this instance I would always consider a hybrid option.  You may get 10 plus months out of the year the gas valve doest turn on, but the guarantee is there you will make set point no matter what.

If you live a place like northern VT with a -20 design temperature  you should have redundancy, wood stove or pellets with heat pump only.  

dko

Jamie Hall said:

Hot_water_fan said:

@Jamie Hall ha don’t you think most Americans have better things to do? I think it’ll just be whatever the contractor or builder decides. 

Which is why I think it is the responsibility of the contractor or the builder to do this. I don't think the average homeowner wants to -- or is qualified -- to make the necessary comparisons, and the politicians certainly aren't. Some contractors are well qualified to do this -- many of the folks here on the Wall, for instance. Unhappily, even more are one trick ponies, and will sell you what they have whether it will work well for you -- or even work at all. The homeowners often don't help -- the tendency is to go for the lowest price, or quickest install. In their defence, they often don't know any better.

I can say with full confidence, the people on here are the 1% of well qualified contractors. Which makes this place a gem.

BirchwoodBill

I think it really depends on the heating zone and on the home-owner. As a homeowner/retired engineer it is my job to create the initial drawings and engineering specifications - then work with the selected contractor to fine-tune the drawings and specifications to what they are able to perform. (For instance, I installed the controls and set up the curves for my current system). I also make the contractor swear on my copy of Siggy's books that they will not try to violate good hydronic design

The math for Zone 6A/Zone 7 - shows a hybrid system being more economical below 8F for a 24K BTUh. Air to water heat pumps really shine where the heat-load is below 8K BTUh.

Hot_water_fan

I can’t believe I forgot one of the hybrid’s best attributes! They can fit better on an electric service, letting you keep a 100 amp panel more easily. 

SHS111

Not a contractor, but a homeowner here. Having had central HVAC (ductwork with heat pumps) installed a few months back, I definitely prefer having the gas-fired boiler for heat. I'm in Massachusetts, and while the heat pumps work perfectly well down to a certain temperature, I far prefer the hydronic radiant heat from convection radiators (house was built in 1935) than warm air heat from the duct system in the ceiling.

DXCoolguy

With the push of electrification, though I still believe a high efficiency gas furnace depolyed at the point of use is still the best carbon reduction strategy, I believe the dual-fuel option is the most realistic option to account for design condition days and further to reduce grid stress as the proliferation of "all-electric" is materializing. Ultimately with smart thermostats and an "opt-in" utility companies can switch dual-fuel customers to burn gas when electric grid stress occurs and switch to heat pump options when electricity is in surplus such as off-peak hours. All electric in a Northern climate isn't a sensible idea considering the condition of our grid. As old nuclear reactors are removed from the grids the electricity retailers will face more and more challenges when faced with extreme grid days. Remember we hear that Con-Ed and PSEG and First Energy remind us that the grid gets stressed out when trying to keep indoor temperatures 15-20 degrees cooler than outdoor on a 95 degree day, the winter model has a much bigger spread, for example a 5 degree day in NY/ NJ is a 65 degree spread between our typical heat set points, though the fact that the coldest part of the day happens when other demands are not high, still even 20 degrees to 70 degrees is a lot of mechanical work to move that heat from outside to inside further if consumers buy into all electric and give up gas in place of resistive elements, the grid will become further stressed.

Jack

Depends upon the house and location. Every building has a personality. Some Jekyll, some Hyde. What I did in our last house in the Sierra Foothills was Fujitsu mini-splits which coupled with my solar system ran the property comfortably at zero cost. That said, I also ran a Rinnai Energysaver in one area of the house and consider the combination to be ideal…for me. In our long term outages the Generator worked well as long as the propane co could get tot the house. Only took 3 weeks last Feb;(, so two cold weeks.
After a massive downsize, now in a 1400 sq ft with a conventional 3 ton oversized, of course, Lennox and 95% gas furnace, if this thing stutters I’d go a 24/36K Fujitsu condensing unit and the appropriate air handler using the existing ductwork, if the duct would support the effort. I’d prefer to eliminate the duct as I did in the last house and go with three evaps.
Net/net, for me I’d eliminate most of the gas use. I am tearing out an old zero clearance fireplace today and replacing with a Rinnai 80+% modulating fireplace, which I am convinced will heat the house and at max input be less than half the input of the single stage 95%’er.

ncalhvac

A hybrid hydronic system seems better because it can adapt to changing energy sources. On the foggy North coast of California where electricity costs 40 cents, gas is a good option, except when gas prices spike and a heat pump is more cost efficient. It's almost always heating season, but the moderate temperatures make for great air HP COP. PV was an option, but now they barely pay anything for grid tie surplus in CA. I would want to go all electric with solar up north away from the coast and have cordwood backup for really cold clear winter nights.

TAG

Depends on house size and location. Heat pump with strips may be perfect in SC where the two loads are about the same. I did a two speed Heat Pump in my 2ksf home and it runs in first stage most of the time winter or summer. Not the case in the Mid - Atlantic. I have multi properties and my Carrier 5 speeds are running flat out on high much of the time in the winter if I use them ... for me it's a sound issue ... even with proper ductwork. Same with the mini splits -- they are better but on high much of the time. The nice thing about a furnace -- the new ones are silent and they can be sized properly. The heat pumps in mid- Atlantic have to be sized for AC or they are too big ... plus even a 5T may not be big enough and the strips are a killer to operate with our electric rates. Small houses gave more options

weatherman

Jamie Hall said:

Too many variables. Which might be better in any given application depends, among a host of other things, on what the client's objective in choosing a heat pump (hybrid or straight) is in the first place, electricty or other fuel costs in the area, climate in the area, client's tolerance to no heat/low heat situations, etc.

Even the first one -- objective -- is murky, as the preferred choice should take into account whether the objective is visible green, actual green (which is very different in most of the country), compliance with a mandate (which is no choice at all actually), or just being comfortable at a reasonable price.

I agree with Jamie. Cost per unit of heat between all of the available fuels and back up redundancy for equipment failure or loss of power.

farmwi

Enjoying the commentary.
What I'm hoping to see is a 2kW (gas/propane) hybrid engine driven heat pump with thermal friction/exhaust recovery. Preferably water jacketed for recovery and noise reduction. That would provide about 6800btu plus addition of COP moved heat of a heat pump, without the need of high grid supplied power, rather for starting and controls. Conceivably, heat and power could be supplied. CHP.
I've also wondered why solar gain isn't leveraged also on the heat pump side.
I'm just surprised there's not a minisplit conversion kit on amazon by now.

Jamie Hall

The best and cheapest way to leverage solar gain is to build a passive solar house. Been saying that for decades, and doing it for about the same length of time. Nobody listens...

bio_guy

Live in TX or some other place where electricity prices can vary by the minute to sky-high prices? (Maybe they fixed that problem that resulted from deregulation that dates back to their little Enron problem.) If so, better go to gas, but is their gas delivery system also susceptible to cold temp problems?

You can run a lot of heat pump with a relatively small backup genset if you have the right heat pump. Inverter systems (and maybe DC-compressor systems) have virtually no start surge. If you are there to step down a whole house heat pump, or can control it remotely, you might be able to run the whole system at fractional capacity. On the other side of the inverter coin are inverter gensets. As power demand drops off, fuel efficiency does not nearly as much.

bio_guy

Over sizing heat pumps for heat can be a good thing since they work most efficiently at partial capacity (as do boilers and furnaces). The trouble is that it is bad for cooling where good humidity control is important.

Hot_water_fan

Live in TX or some other place where electricity prices can vary by the minute to sky-high prices? (Maybe they fixed that problem that resulted from deregulation that dates back to their little Enron problem.) If so, better go to gas, but is their gas delivery system also susceptible to cold temp problems? 

This only happens if you’re on a real time electricity plan. I’m not sure any of those providers actually survived the winter storm. 

I assume most all Texans are on a fixed rate of some sort.

KME

In northern climates, a heat pump sized for the full heating load might be oversized for cooling. Besides higher first cost, there's the problem of short cycling and reduced dehumidification on cooling.

For a case study with an operating cost analysis of a heat pump conversion, see my linkedin post:

https://www.linkedin.com/posts/kennethelovitz_considerations-when-converting-to-heat-pumps-activity-7158099747063386114-Geu5?utm_source=share&utm_medium=member_desktop

Also, Caleffi's video on Dual Fuel Air/Water Heat Pumps with John Siegenthaler is well done and informative. Here's the link:

https://www.youtube.com/watch?v=boqkZD9f7bc