Results of Heat Pump on Electricity Usage

[Romer]

I ended 2022 with two older HVAC systems

• System 1 Goodman Furnace- 10 SEER AC- all 18 years old. (Guessing SEER closer to 6 actual due to age??)
• System 2 Goodman Furnace 18 years old, 13 SEER AC - 9 years old

In another thread I went over all the options and my decision to replace System 1 in January with a Daikin 96% Furnace and Daiken 17 SEER Heat Pump. I will replace System 2 in the next few years

July 2022 and July 2023 is a good comparison of performance even though 2022 was much warmer with 3 days over 100 deg

Here are comparisons of July for both years Replacing only System 1 in 2023. Daily Temperatures are across the bottom of both graphics

Original Systems

New System 1 with Heat Pump

Observations:
•2022 was a product/usage deficit of 350 kWh vs 2023 was a surplus of 440kWh. A 790kWh delta
•2022 average temperature was 4 degrees hotter and had 3 100+ days where as 2023 had zero days above 100 deg
•2022 used more than generated 20 days. 2023 used more than generated 1 day (Cloud cover)
•In 2022, when temps> 90 deg usage ranged from 61kWh to 90 kWh, 61kWh to 75 kWh when looking at 91-98 to compare with 2023
•In 2023, when temps > 90 deg usage ranged from 50kWh to 55kWh (91-98 deg)


Clouds, temps etc where different so I pulled out two 98 degree days. You can't tell which is the Cloths Dryer and which are the different HVAC systems so we can only compare totals.

The one thing to note, on a 98 degree day changing only System 1 for a more efficient Heat Pump reduced consumption from 75kWh to 52.77 kWh.

It would have been interesting to see how it performed on a 100 deg say. in 2022 usage jumped up as high as 90 kWh

I am very pleased with how the system performs and the difference should help power an eventual EV

I would not expect replacement of System 2 to provide such a dramatic impact. Potentially another 5-10kWh improvement on high 90 deg days as a guess

 

[nakman]

this is great data Ken. 2 questions..

- did your thermostat setting remain constant both years?
- what's your estimated ROI on the heat pump?

 

[Romer]

the system I didn't change has the same settings. The new system is a smart controller with lots of settings. I would say the temp settong is equivalent to what we had last year

I didnt calculate an ROI as I replaced a system that was at its end of life. With tax incentives, the new system is the same price as a basic Furnace AC

Not sure how to do an ROI since it uses less electricity and I don't pay for Electricity anymore. What it does do is it allows me to take on an EV in the next year or two without having to upgrade my solar system which I was quoted $10K for even a simple change

 

[Romer]

I started with a goal to get Solar and batteries to eliminate cost for electricity and possibly add an EV without having to pay for electricity

• 2021 Dec installed Solar
• Jan 2023 replaced one HVAC with High efficiency furnace and 17 SEER Heat Pump
• Jan 2024 replaced second HVAC with High efficiency furnace and 17 SEER Heat Pump
• March 2024 - Purchased Cadillac Lyriq EV. Note both retired so average 15-20 miles a day

Looks like I have met my goals

Here is an update- all on days with equivalent temps and similar solar production to make sure cloud cover not a factor

• 1st graph 2022- 2 AC units, one 10 SEER, other 13 SEER
• 2nd graph 2023- 1 13 SEER AC, 1 17 SEER Heat Pump. Likely dryer running with big spike 17kWh less elec swapping 1 AC out
• 3rd Graph 2024 - 2 17 SEER Heat Pumps. 31kWh less elec swapping both ACs for Heat pumps,

Note in sept 2023 had roof replaced and they also modified venting from individual to one that runs along roof line. No data to separate any impact that might be having

I figured this would offset enough to take care on an EV. A few more clouds and a bit less production with similar temps to above with EV charging

 

[Romer]

I should also comment that I use more electricity in the winter with the Heat Pump providing Heat above 35 deg F ( Outside) and also running a 1500W elec heater in the other (Insulated detached) garage to maintain above 42 deg F to keep campers above freezing.

I still expect a surplus at the end of the year. So far running a 400kWh surplus from Jan to today. Surplus at end of year takes care of Electricity until production becomes greater than use in March

 

[gungriffin]

I should also comment that I use more electricity in the winter with the Heat Pump providing Heat above 35 deg F ( Outside) and also running a 1500W elec heater in the other (Insulated detached) garage to maintain above 42 deg F to keep campers above freezing.

I still expect a surplus at the end of the year. So far running a 400kWh surplus from Jan to today. Surplus at end of year takes care of Electricity until production becomes greater than use in March

I was pretty shocked at how much electricity my heat pump uses in the winter. My heat pump was able to keep up when the temps hit -19 f this last winter, but it was pulling 6.5 kw while running and it was running a lot. I had one day where the heat pump used almost 100 kwh in a single day. I had to change the defrost to a stronger setting to have it be able to keep up. My insulation and air sealing wasn't finished in the house on those days though. So that was probably about 50% of the usage.

This is really good and interesting info. Thanks for posting it up.

 

[Romer]

I was pretty shocked at how much electricity my heat pump uses in the winter. My heat pump was able to keep up when the temps hit -19 f this last winter, but it was pulling 6.5 kw while running and it was running a lot. I had one day where the heat pump used almost 100 kwh in a single day. I had to change the defrost to a stronger setting to have it be able to keep up. My insulation and air sealing wasn't finished in the house on those days though. So that was probably about 50% of the usage.

This is really good and interesting info. Thanks for posting it up.

Thanks for that data, makes me glad I went with the Dual System where I can set when the Heat pump triggers on for heat. Currently at 35 deg F, may adjust up a few degrees if the year in total doesn't have a surplus. I like the idea of not having to pay for electricity

 

[gungriffin]

Thanks for that data, makes me glad I went with the Dual System where I can set when the Heat pump triggers on for heat. Currently at 35 deg F, may adjust up a few degrees if the year in total doesn't have a surplus. I like the idea of not having to pay for electricity

That is pretty sweet to have locked in your electricity costs for the next 20-30 years!

 

[Romer]

Now that the hot part of the summer is over, good time to compare two older AC units with two Heat pumps

Here is 20222 with a 10 SEER and 13 SEER older AC units. I have two systems

As you can see two older ACs would use 2mWh of elec in July and August. Two Heat Pumps would use no more than 1.25 mWh and that included the EV charging.

It does use a bit more electricity in March and April to heat, but some of that was the EV as well. I had it set to take over at 35 deg. I changed it to 40 deg just to see how that would do this winter. Gas is pretty cheap again and that 5 deg won't cost much. My Garage heater uses a lot of electricity when it is down or below 0. I may adjust it back next year once I see a full season

Here is 2024 so far with 2 17 SEER Heat Pumps AND an EV. Though we are retired so don't drive as much as we use to. I also added a garage electric heater is why Jan and Feb are higher

 

[Romer]

Something of note. The Heat Pumps are the most efficient way to heat the home. That doesn't mean they are the most cost effective. It is a balance. I had my Heat Pumps set to come on at 35 deg for heat. This took a lot of electricity part way through October. On it's own it wouldnt have mattered as the Solar System produced enough to cover it

But now I have an EV. I decided to reset the Heat Pumps to 50 (outside temp) I would rather pay for a little gas then end up paying for electricity. It is a balance So I will see how it goes over this winter and possibly adjust down to 45 deg.

In the morning when the thermostat raised the house temp setting, the gas furnace kicks on to heat the home. If and when it get above 50, the Heat Pump maintains until it drops back down in temp. The last few days the solar system hasnt been producing (some today) due to the snow and also the shorter days impact production.

My message is I am finding the right balance between usage and production usinge the HVAC Dual system capabilities.

There is significant Net Credit from the time without an EV, so I have lots of margin to play with

 

[Romer]

Just amazed how big a difference Heat Pumps make especially over older AC Units

July 9, 2022 100 Deg F AC units- Consumption 89.42kWh

3 years later July 9, 2025 high temp 102 F Two Heat Pumps- Edit: Consumption 46.35 kWh

Thats almost 50% less consumption for the day

 

[mcgaskins]

Just amazed how big a difference Heat Pumps make especially over older AC Units

July 9, 2022 100 Deg F AC units- Consumption 89.42kWh

3 years later July 9, 2025 high temp 102 F Two Heat Pumps- Edit: Consumption 46.35 kWh

Thats almost 50% less consumption for the day

Very cool (pun intended). How much solar did you generate on the same day out of curiosity?

 

[Romer]

60 kWH yesterday

 

[Romer]

Oh and 67.17 kWh on July 9, 2022 assume there were no clouds that day