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Anyone regret switching to electric heating?

arnolddeleon

Active Member
Supporting Member
Jul 21, 2012
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SF Bay Area
A house that already has central AC shouldn't need any significant of electrical changes. My rental house in Sunnyvale,CA I just converted to a Mitsubishi central heat pump there two small electrical changes for it. The breaker was reduced (I guess some inspectors are sticklers for making it match the plate rating). Electrically this was not needed since the wire was sized for the previous larger drawing unit. The second thing that we had to was add an 120V electrical outlet within 25' of the outdoor unit. Apparently this is a code requirement. I'm guessing to make it easy for future HVAC people to service the unit.

Put another way, if you have central AC and you are looking to replace it (for whatever reason), you should seriously consider a heat pump. In some cases you can keep your existing gas furnace as the air handler and for backup heat.
 

jboy210

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Supporting Member
Dec 2, 2016
7,280
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Northern California
A mini-split sounds like it would serve your office quite well. Any competent HVAC contractor should be able to quote the job pretty easily.
What is the power draw for a room sized (20' X 18') system? And does this make sense if I only need the cooling part since the whole house heating works fine in the winter.
 
Look into TECH Clean Clean California incentives. They are currently out of funding in most areas but they should get more funding. The incentives can be significant, like $6K. They will want you to replace your AC and furnace with a heat pump.

When my heat pump died I was looking into them but didn't qualify because I already had a heat pump. I also didn't like it because I have a dual fuel propane/HP system and didn't want to give up the furnace (but there is a loophole for dual fuel systems).

I have a lot of power outages in the winter where I live and I can run the furnace off a small generator. Many of the AC contractors wanted to remove my furnace and go all heat pump. My wife said if I get rid of the furnace part of the deal would have to be a new generator that could run the heat pump so it didn't turn out cost effective for me.

I'll go 100% electric when PG&E becomes 100% reliable.
 
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Socal Gas changes their base tier of therms every month. Even after I switched to Heat pump, our gas water heater + clothes dryer + cooking usage was still at or above the base.
The charges for over baseline therms are more expensive than the equivalent heat pump KWh, and are likely to go up.

Switching water heater to heat pump too was the only way to stay reliably in the base tier. No regrets, no stress when they call for "please reduce natural gas usage" next winter.
 
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How much was the mini-spilt? We have one room, my office, that is on the West side above the garage and gets pretty toasty in the summer.

Also, does anyone have a similar situation, room above garage, and have any thoughts of cooling?
$4.5 two room split with install. One unit in our main family room and other other in our bedroom.

Our central AC is too small for the whole house. It would have been $13k to upgrade our central AC. So we closed the registers to these two rooms and put in a mini split instead.
 
What is the power draw for a room sized (20' X 18') system? And does this make sense if I only need the cooling part since the whole house heating works fine in the winter.
1-1.5KW, will sip less than that if you get a nice one that modulates output. Cooling-only units are certainly cheaper than full heat pump,.
DIY Mr Cool units are more expensive, they charge more for their refrigerant-shipped-in-the-pipes patent, and the units themselves aren't the best performance, there are lots of good brands either way.
It makes sense if your central cooling can't keep up for that one room.
 
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BGbreeder

Active Member
Jun 19, 2020
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791
Bay Area
Garage door is insulated. My father-in-law was in garage door manufacturing in Wisconsin and drilled that into me. However, it still gets very hot in the garage, 100+ even after the sun goes down. And the garage faces due North so the sides of the garage get sun from 6 Am to 7 PM. The office floor cavities are filled with insulation. But the office floor and walls up to your hips hang like a rectangular box into the sloping garage roof. So, the floor, and 3 of the 4 walls are partially exposed to the 100+ degree temp of the garage. I try to open the garage door in the evening and morning, but even then, the office can be in the 80s at 10 PM. If you walk to the next bedroom down the hall, it is in the mid to upper 70s.

I am talking to my contractor about putting vent fans in the side of the garage. But they are skeptical that they will have much of any effect since the ambient temps in the Tri-Valley are high-90, low 100s from 10AM into the early evening, most of the summer.
You might look into an exhaust fan controlled by a dual temperature controller (like the ones used for solar water heating). You can set the fan to exhaust warm air from the garage space whenever it is warmer inside than out. You can then leverage any overnight cool down to precool the garage before the next day.

All the best,

BG
 

jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
7,280
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Northern California
You might look into an exhaust fan controlled by a dual temperature controller (like the ones used for solar water heating). You can set the fan to exhaust warm air from the garage space whenever it is warmer inside than out. You can then leverage any overnight cool down to precool the garage before the next day.

All the best,

BG
A temperature triggered exhaust fan is what I have been talking to my contractor about and they were sort of wishy-washy on how well it would work. However, maybe I try that first since it is cheap and relatively easy. Also, since my Powerwalls are in the garage it would help keep them cool, or at least move some air by them.
 

BGbreeder

Active Member
Jun 19, 2020
1,113
791
Bay Area
A temperature triggered exhaust fan is what I have been talking to my contractor about and they were sort of wishy-washy on how well it would work. However, maybe I try that first since it is cheap and relatively easy. Also, since my Powerwalls are in the garage it would help keep them cool, or at least move some air by them.
My beef with standard temperature triggered fans is that they turn on at a preset temperature. What I want for my garage is for it to only turn on when the air outside is colder than the inside, thereby cooling the garage. I don't need a fan set for 85F on if it is 95 outside and 85F inside the garage. That just makes the problem worse.
Something like this, set for temperature difference mode; (I haven't used this one)
https://www.amazon.com/diymore-Temperature-Controller-Thermostat-Greenhouse/dp/B096LVFTBK
This one does 220;

All the best,

BG
 
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jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
7,280
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Northern California
My beef with standard temperature triggered fans is that they turn on at a preset temperature. What I want for my garage is for it to only turn on when the air outside is colder than the inside, thereby cooling the garage. I don't need a fan set for 85F on if it is 95 outside and 85F inside the garage. That just makes the problem worse.
Something like this, set for temperature difference mode; (I haven't used this one)
Amazon.com
This one does 220;

All the best,

BG
Good point. I will look into this.

Update. Rating not so good on this one. But, the idea is good. Thinking out loud, I could probably build something with a microcontroller, some temp probes, DC controlled AC switch. And maybe put it on my IoT network so I can control it remotely. No use doing something unless you can overdo it!
 
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I am trying to be as green as we can and considering switching to a heat pump. However, I am not sure the numbers make sense.

We are in the SF East Bay. In the winter months, we don't generate much because of low sun, big old trees, and cloudiness/fog. We are lucky to get 8-9 kWh/day at the winter solstice in these conditions. This is about 85% of our home use with gas heating. If we happen to hit a stretch of clear weather, we might jump up to 14 kWh/day. Home is 3100 Sq feet over 2 floors. Insulation, windows, and doors have all been replaced in last 8 years, so it is pretty tight.

We have 2 Teslas, a 3 and X, and drive about 5K/year total and charge 60% of the time at home.

As much as I would like to do my part to decrease emissions, I am not thinking this makes any financial sense. Also, I do not want to be wishing after year I was still on gas heating as I stare at a large electric bill. Gas bill is up to $125/mo. What do others think?
ASHP are pitiful with outside air temps below 9C
A GSHP would perform better with the weather you describe.
 

arnolddeleon

Active Member
Supporting Member
Jul 21, 2012
1,070
1,151
SF Bay Area
ASHP are pitiful with outside air temps below 9C
A GSHP would perform better with the weather you describe.

It's not clear if you are making a case about efficiency or $.

A ground source heat pump will thermodynamically do better because it has a more consistent source/sink for the heat. But it will be more expensive to install and possibly never offset that difference.

A common fallacy assumes that you will be at the worst condition the entire winter.

The SF East bay does not spend that much time at below 9C. Modern air source heat pumps stay above an efficiency of 1 at far lower temperatures. If conditions warrant it then you could always fall back to emergency heat, the worst case being resistance heat which gives you an efficiency of 1. Basically as long as you electricity you have heat.
 
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It's not clear if you are making a case about efficiency or $.

A ground source heat pump will thermodynamically do better because it has a more consistent source/sink for the heat. But it will be more expensive to install and possibly never offset that difference.

A common fallacy assumes that you will be at the worst condition the entire winter.

The SF East bay does not spend that much time at below 9C. Modern air source heat pumps stay above an efficiency of 1 at far lower temperatures. If conditions warrant it then you could always fall back to emergency heat, the worst case being resistance heat which gives you an efficiency of 1. Basically as long as you electricity you have heat.
I don’t disagree ! 👍😂
 
ASHP are pitiful with outside air temps below 9C
A GSHP would perform better with the weather you describe.
Well, "pitiful" seems a bit strong to me. We installed a Mitsubishi ASHP to replace our gas furnace in January 2021. It uses air ducts just like furnaces do, with the air handler placed in the location of the furnace. We don't have back up heating, but it has been 30 years since we last had outside temperature below freezing. Mitsubishi publishes the performance in tabular form, and here is a graph of the EER vs outside temperature. Once can convert the EER to COP by multiplying by 0.293 Wh/BTU. BTW, at 32F, the maximum heat output is still 90% of nominal capacity.
KP30.png
At todays PG&E TOU-C and gas rates, the cost of heating (if we didn't have solar) would be about 25% higher using the heat pump than a 95% efficient gas furnace.
 
Switched to a heat pump for central house heating in 2019 and a heat pump water heater in January 2021.
Cost for house heating decreased 30-40% using the heat pump vs gas.
Bill for water heating decreased 50%.

It was a great decision with no regrets.
Here in coastal SoCal, the weather is excellent for heat pumps, even in the winter. Depending on where you live, your mileage may vary.

EDIT: the only caveat is that heat pump water heaters recharge hot water much more slowly than gas, so I would recommend spending the extra to get a larger 80+ gallon tank if you go that route.
 
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h2ofun

Active Member
Aug 11, 2020
4,006
1,014
auburn, ca
Switched to a heat pump for central house heating in 2019 and a heat pump water heater in January 2021.
Cost for house heating decreased 30-40% using the heat pump vs gas.
Bill for water heating decreased 50%.

It was a great decision with no regrets.
Here in coastal SoCal, the weather is excellent for heat pumps, even in the winter. Depending on where you live, your mileage may vary.

EDIT: the only caveat is that heat pump water heaters recharge hot water much more slowly than gas, so I would recommend spending the extra to get a larger 80+ gallon tank if you go that route.
This is reason I stayed with a propane water heater, even though I also have solar water heating panels.
 
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jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
7,280
4,948
Northern California
Your office is hot because the garage is hot.
The garage is hot due to full on sun, and the insulated garage door prevents ventilation

My thoughts stray to shading the garage
We have vents on the side walls and above the garage door. Where we do not have vents is a peak of the garage. That where I talked to my contractors about installing the extractor fan.

Shading the garage is something we were thinking about doing since the inverters are on the outside of the west facing wall. And I have noticed on really sunny and hot (100+) days, the inverters seem to be derating. We are thinking about getting a shade sail that would cover a significant portion of this wall.
 
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jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
7,280
4,948
Northern California
Switched to a heat pump for central house heating in 2019 and a heat pump water heater in January 2021.
Cost for house heating decreased 30-40% using the heat pump vs gas.
Bill for water heating decreased 50%.

It was a great decision with no regrets.
Here in coastal SoCal, the weather is excellent for heat pumps, even in the winter. Depending on where you live, your mileage may vary.

EDIT: the only caveat is that heat pump water heaters recharge hot water much more slowly than gas, so I would recommend spending the extra to get a larger 80+ gallon tank if you go that route.
Any thoughts on tankless? Right now we have a tankless gas system and recirculation pump to ensure we have hot water in seconds instead of minutes in the master bathroom at the far end of the house.
 

jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
7,280
4,948
Northern California
It's not clear if you are making a case about efficiency or $.

A ground source heat pump will thermodynamically do better because it has a more consistent source/sink for the heat. But it will be more expensive to install and possibly never offset that difference.

A common fallacy assumes that you will be at the worst condition the entire winter.

The SF East bay does not spend that much time at below 9C. Modern air source heat pumps stay above an efficiency of 1 at far lower temperatures. If conditions warrant it then you could always fall back to emergency heat, the worst case being resistance heat which gives you an efficiency of 1. Basically as long as you electricity you have heat.
Requiring higher amounts of electricity is part of the problem I see with going to a heat pump. In the winter the solar sometime only generates 9-10 kWh a day, which does not meet our needs, let alone charge the powerwalls. And with 50% or so PW reserve levels we have 14 kWh in the 2 powerwalls. So in a power outage we don't have much reserve to run a heat pump.
 

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