CPUC NEM 3.0 discussion

[wwu123]

that guy is hard to listen to for 20 minutes
Not many Heat Pumps have COP of 2.5 at cold temps which is the breakeven point compared to burning NG at home. But, my comparison was cost using my rates for NG and Electricity. It would be cheaper for me to burn NG. That said, I installed a heat pump 2 years ago because I have solar and my old gas furnace was dying, but it is only for half of my house. It is a 16 SEER heat pump. I'll have to look up the COP for heating. Since the gas was plumbed there already, I got a unit with gas as the backup. My experience with the unit is that for outside temps below 40 degrees, it has a hard time. That is not very cold. For example, on colder nights, that portion of my house can get down to 66 degrees. If I only use heat pump mode, it takes a long time to bring the temp up to 72 degrees., on the order of 4 hours. S

In California, where in winter it gets cold each night but often warms up to 60s or even 70's during the day, does it make sense with dual-fuel to run the furnace in the morning to recover temps, and the heat pump during the middle of the day when it's COP/efficiency is better? I know most of the heating needs are in the morning, but we do have some north-facing rooms zoned that the heat can kick in all day.

We have a 10-year-old Carrier 95% furnace in good shape, but no A/C unit. Thinking about adding A/C for cooling just a few weeks each summer, may as well make it a heat pump since we run the heat 7 months a year even in the mild Bay area climate. Still don't understand why heat pumps are almost twice the price installed as an A/C unit, even though they are basically the same hardware just with a few additional parts (reversing valve, etc...)

 

[getakey]

In California, where in winter it gets cold each night but often warms up to 60s or even 70's during the day, does it make sense with dual-fuel to run the furnace in the morning to recover temps, and the heat pump during the middle of the day when it's COP/efficiency is better? I know most of the heating needs are in the morning, but we do have some north-facing rooms zoned that the heat can kick in all day.

We have a 10-year-old Carrier 95% furnace in good shape, but no A/C unit. Thinking about adding A/C for cooling just a few weeks each summer, may as well make it a heat pump since we run the heat 7 months a year even in the mild Bay area climate. Still don't understand why heat pumps are almost twice the price installed as an A/C unit, even though they are basically the same hardware just with a few additional parts (reversing valve, etc...)

Mine has an setting that you can tell it to use gas until the outside temp reaches a certain degrees. I set it to 45 degrees. So it uses gas in the morning on cold days.

 

[wwu123]

Mine has an setting that you can tell it to use gas until the outside temp reaches a certain degrees. I set it to 45 degrees. So it uses gas in the morning on cold days.

At current PG&E gas and electrity rates, I think I'd need a COP of about 3.0 for heat pump to be cheaper than gas furnace, though tiers and baselines for both fuels do complicate the equation. I think I could certainly get that mid-day most winter days around here, not sure about in the morning. What do you think your COP is at 45 deg for your 16 SEER?

I'm looking at a few inverter heat pumps, like the Bosch or Daikin FIT, that can work with an existing air handler/furnance, prob the Bosch as it's compatible with smart thermostats like my Ecobee for easy dual-fuel setup. They are supposed to have amazing COP/efficiency. Though installers that cover these brands are very few and far between, and one said the Bosch is very backordered, that he didn't even bother to quote or call back....

 

[BGbreeder]

@wwu123 if you are looking to add a heat pump to an existing furnace, I would consider the age of the furnace. You would be duplicating a lot of labor costs if you have to switch it out in a few years. Older gas furnaces tend to have relatively inefficient air handling fans. Moving heat in or out is only part of the energy / overall efficiency story. Heat pumps work best by running fans for much longer periods of time, but often at lower air speeds, and unless you have a more modern fan/air handler, you will incur significant additional energy costs as the furnace fan will run at a higher than optimal speed for the heat pump, which tends to generate colder air in circulation (drafts). YMMV...

All the best,

BG

 

[getakey]

At current PG&E gas and electrity rates, I think I'd need a COP of about 3.0 for heat pump to be cheaper than gas furnace, though tiers and baselines for both fuels do complicate the equation. I think I could certainly get that mid-day most winter days around here, not sure about in the morning. What do you think your COP is at 45 deg for your 16 SEER?

I'm looking at a few inverter heat pumps, like the Bosch or Daikin FIT, that can work with an existing air handler/furnance, prob the Bosch as it's compatible with smart thermostats like my Ecobee for easy dual-fuel setup. They are supposed to have amazing COP/efficiency. Though installers that cover these brands are very few and far between, and one said the Bosch is very backordered, that he didn't even bother to quote or call back....

I did the calc using COP=3 and NG is cheaper. Not sure on my COP at 45 degrees. I need to get my model number and look it up. From a practicality point of view, NG provides better comfort below 45

 

[h2ofun]

In California, where in winter it gets cold each night but often warms up to 60s or even 70's during the day, does it make sense with dual-fuel to run the furnace in the morning to recover temps, and the heat pump during the middle of the day when it's COP/efficiency is better? I know most of the heating needs are in the morning, but we do have some north-facing rooms zoned that the heat can kick in all day.

We have a 10-year-old Carrier 95% furnace in good shape, but no A/C unit. Thinking about adding A/C for cooling just a few weeks each summer, may as well make it a heat pump since we run the heat 7 months a year even in the mild Bay area climate. Still don't understand why heat pumps are almost twice the price installed as an A/C unit, even though they are basically the same hardware just with a few additional parts (reversing valve, etc...)

why need dual fuel? I live in the foothills, which get colder than you. I am a mini split setup. Has no issues working with in the 20's outside.

 

[Big Dog]

I did the calc using COP=3 and NG is cheaper. Not sure on my COP at 45 degrees. I need to get my model number and look it up. From a practicality point of view, NG provides better comfort below 45

72 degree room temp is 72 degree room temp. Nat gas just gets it there faster. OTOH, a HP can keep it at the desired temp constantly.

 

[getakey]

72 degree room temp is 72 degree room temp. Nat gas just gets it there faster. OTOH, a HP can keep it at the desired temp constantly.

yes, NG gets it there faster (and cheaper). Thats what I meant.

 

[tomuo]

yes, NG gets it there faster (and cheaper). Thats what I meant.

I think there's a red pill moment here. Is heating faster actually a requirement? and cheaper is true currently only if you ignore the externalities of burning NG, and ignore that NG gas prices will go up but your locally sourced solar electric will not.
Mini spilt heat pumps have worked well below freezing for years. Larger systems are finally catching up to that performance.

 

[getakey]

I think there's a red pill moment here. Is heating faster actually a requirement? and cheaper is true currently only if you ignore the externalities of burning NG, and ignore that NG gas prices will go up but your locally sourced solar electric will not.
Mini spilt heat pumps have worked well below freezing for years. Larger systems are finally catching up to that performance.

electricity at night is primarily using NG power plants. So running heat pump overnight is virtually same if not worse if air temp is low

 

[tomuo]

electricity at night is primarily using NG power plants. So running heat pump overnight is virtually same if not worse if air temp is low

Yes, that's still part of the point. Worst case, on the coldest night (10-15 a year in Chicago), performance is the same, and only worse for older heat pumps.
Every other day, or with a modern system, it's a win.
If you live in those climates, just limit your choice to an effective system instead of the cheapest.

 

[getakey]

Yes, that's still part of the point. Worst case, on the coldest night (10-15 a year in Chicago), performance is the same, and only worse for older heat pumps.
Every other day, or with a modern system, it's a win.
If you live in those climates, just limit your choice to an effective system instead of the cheapest.

not all new heat pumps perform that well below freezing. Look at real life units that you can buy

 

[aesculus]

72 degree room temp is 72 degree room temp. Nat gas just gets it there faster. OTOH, a HP can keep it at the desired temp constantly.

That's why I changed my heating strategy this winter when I installed a new variable speed heat pump. For the core of the house I just lowered the temp 1*F overnight and in the sleeping areas, 2*F. All with 0.5*F differential.

The HP can come on in the middle of the night for a 1/2 hour or so a few times to "top off" the temperatures at the lowest of settings. I don't even know that it is running. And then at 6 AM while still on Off Peak, I restore the temperature to their daytime values. It usually took a few hours to come back up, but generally all on HP mode and not secondary (resistive) heating like it would have with my old HP and a bigger nighttime setback.

From glancing at my bills from years prior and this winter, it looks like it was much more economical. And the best part is that it was very quiet too. At the low speed, even though an 4 ton unit is outside my window right next to my bed, I only heard it if I was already awake.

 

[wwu123]

@wwu123 if you are looking to add a heat pump to an existing furnace, I would consider the age of the furnace. You would be duplicating a lot of labor costs if you have to switch it out in a few years. Older gas furnaces tend to have relatively inefficient air handling fans. Moving heat in or out is only part of the energy / overall efficiency story. Heat pumps work best by running fans for much longer periods of time, but often at lower air speeds, and unless you have a more modern fan/air handler, you will incur significant additional energy costs as the furnace fan will run at a higher than optimal speed for the heat pump, which tends to generate colder air in circulation (drafts). YMMV...

All the best,

BG

It's 11 years old, but it's a 95% efficient, top-of-the line Carrier, and 90% of the time the ECM motor is running < 100W in low stage heat, so very efficient And since we don't currently have AC, the fan and motor haven't been in use half the year. So I do think I'll get at least another 10 years life out of it - certainly a newer furnace wouldn't be any more efficient. But I hear you on the typical kw-guzzling 500W+ PSC motors....

 

[wwu123]

why need dual fuel? I live in the foothills, which get colder than you. I am a mini split setup. Has no issues working with in the 20's outside.

Cause I already have the single fuel (gas), with high efficiency, and need to amortize the sunk cost for a few more years. Believe me, I would also gladly install a DIY Mr Cool mini-split myself, the room that needs the most heating all day has a perfect spot for one, with the main breaker panel right on the outside wall. But my wife is from Asia, grew up with mini-splits, and just doesn't like the look of the head unit on the inside wall.

Of course there are ducted mini-splits, or hidden ceiling cassettes, but those need professional install. A friend just installed Mitsubishi mini-splits with multiple head and ceiling cassettes.... well, it's for heat also, but basically it would be 3X the price of just adding A/C or a heat pump to my existing furnace...

 

[getakey]

Watch the latest YouTube from Technology Connections - he explains that Heat Pump heat from electricity made from NG is /still/ more efficient that pumping that NG to your house and burning it locally for heat.

I'll bet money he does not have a Heat Pump or he would have used some real life experience

 

[holeydonut]

Lol @ucmndd

 

[dareed1]

I'll bet money he does not have a Heat Pump or he would have used some real life experience

If you watch his earlier video, you'll see that he does own a heat pump.

Regarding COP, we installed a Mitsubishi system--an outside unit and an interior air handler that is installed where our gas furnace was, so it uses typical house ducting. It is rated at 30,000BTU/h with a COP of 4.2 at 47F and 3.2 at 17F. The system has a thermal cutout if the outside air goes below 15F. They sell systems that can operate at 5F or less, but the COP is not as good. We chose Mitsubishi for quite low external noise and high COP in case we need to run on the Powerwalls for a few hours.

Comparing the gas usage we had before with the electric energy consumption now at PG&E rates, the heat pump is more than 2 times cheaper. The house is more comfortable and the air circulation is inaudible.

But it wasn't cheap....

 

[getakey]

If you watch his earlier video, you'll see that he does own a heat pump.

Regarding COP, we installed a Mitsubishi system--an outside unit and an interior air handler that is installed where our gas furnace was, so it uses typical house ducting. It is rated at 30,000BTU/h with a COP of 4.2 at 47F and 3.2 at 17F. The system has a thermal cutout if the outside air goes below 15F. They sell systems that can operate at 5F or less, but the COP is not as good. We chose Mitsubishi for quite low external noise and high COP in case we need to run on the Powerwalls for a few hours.

Comparing the gas usage we had before with the electric energy consumption now at PG&E rates, the heat pump is more than 2 times cheaper. The house is more comfortable and the air circulation is inaudible.

But it wasn't cheap....

I'll have to look at his earlier one.
I lived in Belmont for >20 years. Perfect climate for heat pump. It never freezes and rarely gets below 40. Where I live now it does not get into the 30s much, but when it does, the heat pump is not good

 

[RKCRLR]

I have a Carrier Infinity dual fuel (propane) heat pump. I have currently my furnace locked out until it gets below 35F. When I built my home in 2009 I wanted the flexibility of being able to select the most economical fuel since electricity rates and propane prices were fluctuating, I wanted the comfort of gas heat, and I wanted to have heat during a power outage. I would set the crossover point of when it switched to gas depending on which was more price effective at the given COP. I subsequently installed enough solar to become a net generator. The gas switchover point is now one of the things I take into consideration to just barely be a net producer since electricity is more economical as long as I'm a net producer. I now mainly use the furnace during a power outage, during the defrost cycle, and to recover from a large setback temperature when it is cold.