Heat pump experience, good or bad

[D Boggess]

This is a story about continued learning by trial and error.

We believe our lifestyle is sustainable although we continue to rely on electricity from the grid at night and on days with rain, snow or extreme cold. 

As you may be aware, heat pump technology is evolving into two categories defined by how they operate in cold weather. The legacy design (for warm weather) can be used for heating in southern states where mild winter temperatures are usually above freezing. Legacy heat pumps also can be used effectively in northern states when paired with a traditional furnace for heating when outdoors is below 40°F. 

Our home had a legacy heat pump until recently when it was replaced by a cold weather heat pump using inverter compressor technology that provides heat when outdoors is below 0° F.  We relied on the new heat pump during the extreme cold weather of 2025. Heating performance seemed acceptable until we noticed the change in our electric bills. Life is full of compromises, and this is another one.

Our solar net metering carries energy credits forward on the bill when more energy is produced than is consumed on site. The kWh credit balance increases during summer and is reduced during winter. Although we believed our thousands of kWh credits in November 2024 would be enough to carry through the winter, it was to be for only one heating season.

We realized that using the heat pump in extreme cold events is not sustainable unless we want to pay for using more electricity.  Heat pumps don't create heat by burning fuel. They transfer heat from a cold place to a warm place. More energy is used as the temperature drops and less heat is in the outdoor air for transfer to the house.  Our cold weather heat pump was running at or near its capacity on very cold days.  The kWh credits remaining in November 2025 would not be enough to carry through the next winter season. 

This winter as an experiment we set the thermostat mode to emergency heat, which allows the backup gas furnace to operate while the heat pump is locked out. Our gas bill increased by $70 /month for the first month and the reduction of kWh credits on the electric bill was about half of the corresponding reduction the previous year.  I'm taking a picture of the dials on the gas meter each week to learn how outdoor temperature affects gas usage by the furnace.

If your priority is to use less electricity from the grid that is generated by burning coal, paying the gas company for a few months in winter may be an acceptable alternative. 

The penalty for using more electricity with the Duke Energy regressive rates is that the first 300 kWh monthly has the highest rate, almost $0.20 /kWh including state sales tax. You get discounts for using more electricity.

The heat pump is a reliable source of air conditioning when we have kWh credits.  In summer the refrigerant cycle is reversed to transfer heat from the house to outdoors.

Alternatively, a cold weather heat pump might be an obvious choice if you have an electric furnace or baseboard resistance heat. Heat pumps use half or less of the amount of electricity used by electric resistance heating.

You can start small with other heat pump applications. Our heat pump water tank and heat pump clothes dryer don't use much electricity compared to the amount of energy needed to heat the house. Our second EV, a 2022 Chevrolet Bolt EUV, uses about 2,000 KWH for driving 8,000 miles annually.

Darrell

[Jim Shackelford]

That is a very good report to have, Darrell. I've been told by Vermont friends their place heats entirely from a newer heat pump in winter.  What they didn't say was the amount of the bills.  My impression was it was very low (it's not a big place, and well insulated), but maybe it's not as low as I imagined.

Jim Shackelford

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[Mike Mullett]

Darrell, Jim -

 

    My wife and I have had a similar experience to that reported by Darrell thus far this winter as a result of replacing our downstairs HVAC system with the most energy efficient system currently available due to a failure in late September of our 20-year old legacy system.  

 

    Presumably, at some point in the not too distant future, we will of necessity also be replacing our upstairs legacy HVAC system, presumably with a similar new model (but on a somewhat smaller scale given the respective sizes of our upstairs and downstairs systems).

 

    The other matter I would report of potentially general interest is that the applicable rebates were forthcoming from both Vectren and Duke.  That said, the (smaller) rebate from Vectren came expeditiously by check, as expected.  However, the (larger) rebate from Duke was tendered initially by a DEI contractor in the form of a limited purpose credit card which required the purchase of a limited range of goods and services which we would have otherwise purchased on our existing general purpose credit card. 

 

    In protesting the substitution of a limited purpose credit card for a check, we (as well as the contractor administering the rebate program for Duke) learned that check or card was, indeed, at customer option.  However, it took an e-mail and phone call exchange with Kelley Karn to get the DEI rebate contractor "on the same page," so it was the end of December before we finally received our rebate check from the contractor. 

 

    Hopefully, our experience will benefit on a more timely basis other DEI customers replacing the electric components of their HVAC systems with the most efficient (and expensive) versions currently available.  If not, I will be happy to provide Kelley's business e-mail address and phone number to any other DEI customers finding themselves in similar circumstances.

 

    Mike 

Michael A. Mullett

723 Lafayette Avenue

Columbus, IN 47201

Phone: (812) 350-0707

E-Mail: mulle...@aol.com 

 

To view this discussion visit https://groups.google.com/a/sirensolar.org/d/msgid/forum/CAJerjm7Zc7j4ihciZTx1asSi9JZJaJRPERp%3DaDMWqc14dqRWAg%40mail.gmail.com.

[Madeline Hirschland]

Darrell,

Thank you for sharing this. It's really valuable. As I read it: using solely heat pumps to heat and cool your home, your demand for electricity exceeded your free supply of electricity from your solar panels. With your current solar array, the cleanest and most cost-effective way to meet that demand is to rely on lower-priced gas-powered heat from your furnace to rather than expensive coal-fired electric heat.

I wondered how many more solar panels you'd need to cover your complete energy needs with energy from the sun and what the payback period would be for those panels.  By my very rough calculation (pasted below), you’d need two, which would cost ~ $2600 up front and save you ~ $480 per year. If so, the panels would pay for themselves in 5.5 years. After that, meeting all your energy needs would cost just Duke's monthly connection fee - currently $14 a month.

We too power all our household energy needs with electricity from our solar panels and, like you, the shift to heat pumps – in our case, three ductless mini-splits – continues to be so interesting. Like a window air conditioner, a mini-split heats and cools a particular zone in your house – no ducts! - independent of other zones. Once you have mini-splits, heating  or cooling your whole home rather than only the part you’re using feels wasteful – like leaving lights on in the entire house when you’re only using one room. As I’ve mentioned here before, in winter, we use our upstairs mini-split upstairs for just an hour before we sleep and leave the downstairs two off until a few hours before we come home from work. That’s all we need - usually. But when it’s bitter cold, we’ve learned we need to keep all three on during the day in order to keep the house warm. 

If you’re thinking about switching to heat pumps and want to see some in action, we’ll be hosting an open house on Sunday, February 1^st.

Stay warm!

Madi

Rough calculation: # of additional solar panels and payback period to cover Darrell's complete energy needs with solar energy generated at home

Cost of installing solar to heat, cool, light, drive etc. solely with solar energy: ~ $2625

~ $70 a month for gas heating during 4 coldest months = ~$280 = ~ 280 therms

280 therms = 99976.1 BTUs = 818 kWHs

In Bloomington, 1 watt of installed solar generates ~ 1.13 kWh of electricity per year

So generating 818 kWhs more per year would take 725 watts more in installed solar

(or two 375-watt panels for a total of 750 installed watts)

750 installed watts x  $3.50 an installed watt = $2625

Annual savings from installing 750 more watts of solar: $476 (more if Centerpoint’s connection fee or price per therm rise)

Save $18 a month Centerpoint connection fee = 12 months x $18 = $196

Save on gas bills during coldest months  ~ $70 per month x 4 months = $280

Payback period: $2625 / $476 = 5.5 years (after which you’d be 100% powered by the sun)

To view this discussion visit https://groups.google.com/a/sirensolar.org/d/msgid/forum/409307887.281280.1768322561281%40mail.yahoo.com.

[Jim Shackelford]

A great response, Madi.  How does one get invited to your Open House?

Jim Shackelford

[Madeline Hirschland]

Thanks, Jim- you're invited! You can sign up here for the open house presentation / Show & Tell. Because space is limited, we'll actually have two back-to-back - one beginning at 2 PM and the other at 3:30 PM. Each will start with a brief presentation on the various electric "appliances" and income-qualified rebates available. You'll then be able to go see the ones that interest you and people who know about them will be on hand to answer questions. (The "appliances" at this open house are ductless mini-split heat pumps, a heat pump water heater, an induction cooktop, ground mount solar panels and, we hope, an EV.)

If these times aren't good for you or space fills up (there's room for 20 people at each and City of Bloomington Energy Navigator! teams will be canvassing for several weekends before to invite people), there are other presentations that you can attend. The one on Feb. 8th also will be a Show & Tell of sorts. Congregation Beth Shalom and St. Thomas Lutheran, neighbors that share a parking lot, are teaming up on that one. The presentation will be at Beth Shalom and the Show & Tell will mostly be at St. Thomas, which has a cold-climate heat pump and ground-mounted solar panels. You also can see Beth Shalom's ductless mini-split. Again, we should have an EV and induction cooktop on hand.

Other upcoming presentations on home electrification will be on Jan. 28th from 6 PM to 6:40 at Green Drinks (Upland Brewery Wood Shop at 350 W. 11th St.) and on Jan. 31 from 4:45 to 6 at the Banneker Center (930 W. 7th St.)

(For now, all these are in Bloomington, organized by Electrify Indiana supported by the City's Bloomington Energy Works program. Once we can catch our breath, Electrify Indiana is very interested in helping other cities do a similar electrification education blitz.  If you're not in Bloomington but are interested in seeing this happen near you, please let me know.)

Hope to see you soon,

Madi

[Jim Shackelford]

We'll see you Feb. 1, Madi.

[Ray Wilson]

I am interested in this situation and possible solutions.  One issue is that the extra heat may be needed in just a few days each month not spread out over a whole month.  Another issue is can you add panels to your present array without losing your net metering situation.  Since solar panels are so cheap, what about installing several radiant heaters like ones used in RVs and run them on DC current straight from the panels thus not worrying about the net metering issue .   

On Thu, Jan 15, 2026 at 2:04 PM Jim Shackelford <jimshac...@gmail.com> wrote:

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[Mike Mullett]

Ray, Jim -

 

    My only input on this topic is that:

 

    1. DIY workarounds are always owner and site-specific;

    2. If a particular grandfathered net-metering customer can add panels without increasing inverter capacity, it should not invalidate that customer's Net Metering status (but who knows what individual Indiana utilities would do anyway unless challenged); however, if adding panels will require an increase in inverter capacity, it would invalidate grandfathered net metering; and

    3.  At this point, DIY is not currently "market-moving" -- certainly not in Indiana with Trump still in the White House; however, should new "off-the-shelf" technologies and business models emerge (e.g., "plug-in" panels, KOPA-type business models) as they might, that could change -- especially with the rapidly rising cost of electricity combined with the dramatically escalating maldistribution of wealth and income and the systematic dismantling of the social safety net in the United States (e.g., the most recent ALICE studies show that 40% of Indiana households do NOT earn sufficient annual income to support more than a bare subsistence budget.)

 

    Mike

Michael A. Mullett

723 Lafayette Avenue

Columbus, IN 47201

Phone: (812) 350-0707

E-Mail: mulle...@aol.com 

 

To view this discussion visit https://groups.google.com/a/sirensolar.org/d/msgid/forum/CABVzCbxVXk1DtSNKE6ELa7pdrRepn2vjgn6Etnt5MEWWf_hSOA%40mail.gmail.com.

[Brad Morton]

All,

I wanted to share this product with you: https://signaturesolar.com/eg4-r32-solar-powered-12k-btu-mini-split-kit/

 

This allows you to connect solar panels directly to the heat pump without have to file any interconnection paperwork with the utility company.

 

Although we haven’t installed any of these yet, we do install the EG4 batteries and inverter products.

 

Almost all of our new residential installations have a battery these days.

 

The value and benefits are enormous, especially if you don’t have net-metering.

 

The challenge with heating your home with solar energy is “when you need it the most, you have it the least.”

 

Brad Morton

President

Morton Electric, LLC

O (812)402-0900 x101

C (812)453-1924

bmo...@mortonsolar.com

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[Mike Mullett]

Thanks, Brad -

 

    I will take a close look at this product.

 

    Mike

Michael A. Mullett

723 Lafayette Avenue

Columbus, IN 47201

Phone: (812) 350-0707

E-Mail: mulle...@aol.com 

 

To view this discussion visit https://groups.google.com/a/sirensolar.org/d/msgid/forum/MWHSPRMB0005B244C0AD7256C949691FB48DA%40MWHSPRMB0005.namprd10.prod.outlook.com.

[Shawn Holsapple]

A few comments:

• EG4 makes a mini split with direct PV & AC inputs.  One could add this unit with 3-4 panels to help offset the additional power draw from the current heat pump without messing with the grandfathered system.
• I have a modern whole house heat pump with propane backup.  Since I don't sell back to the grid, I rely on sunshine and lots of batteries to keep my REMC bill low.  My unit is rated down to 23° and I've seen it run to 20° before stopping and switching to propane.  At that point, we've already got the built-in wood stove cranked up.  I then just turn on the furnace air handler to circulate the wood heat throughout the home.
• On cold sunny days, I'll crank up the temp during the day to heat up the house beyond our normal temperature.  This allows the thermal mass of the home to release the heat during the night without having to run the HVAC much, if any.  The PV system can run the whole house along with the extra heat pump usage and usually still have the batteries topped off @ 100% by dusk.
• By doing this, we average about 6-7 ricks of wood [free from our acerage] & 90-100 gallons of propane a year, all while keeping the REMC bill close to $90 a month or less with 3300 ft.².  Of course having R55 8" walls and R73 rafters with a Net Zero designed home helps.

Please let me know if you have any questions I may assist you with.

Best Regards,

Shawn Holsapple

To view this discussion visit https://groups.google.com/a/sirensolar.org/d/msgid/forum/1726471853.1052274.1768596718496%40mail.yahoo.com.

[Alex Jorck]

Hi all,

Just wanted to share on the grandfathering of net metering front.

At the end of net metering eligibility during 2022, when my solar system went in, Duke made guarantees that they would honor grandfathering status no matter the type or extent of change to a person's solar system. I was very clear and used numerous examples. I was told that even if someone installed a minimal, 3.8 kW AC system and came back and added 11.4 kW AC of additional capacity, that this would not change the net metering status. I was very surprised, I would guess that most IOUs are not thinking this way, but on Duke there is a decent chance that any expansion might be approved without losing net metering. Just obviously check with them before you have large financial commitments to a project.

Best,

Alex Jorck (he/him)

ajo...@gmail.com | 812.371.6197

Commissioner, Bloomington Commission on Sustainability

To view this discussion visit https://groups.google.com/a/sirensolar.org/d/msgid/forum/CAFv2heqk_jFRyMhGMVjGJwO56fSSnPwcuh6mNKscTWqasmFb4g%40mail.gmail.com.

[Erin Moreno]

Can we please remove me from this email list. 

Sent from my iPhone

On Jan 17, 2026, at 8:57 PM, Alex Jorck <ajo...@gmail.com> wrote:



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[Mike Mullett]

Alex -

 

    I do hope you have that commitment in writing from Duke and approved by the IURC because all of the documentation which I have is directly to the contrary.  

 

    In particular, I would direct your attention to the Commission's General Administrative Order 2017-2 (which is still in effect according to the IURC's website), copy attached.

 

    More specifically, I would direct your attention to Sections II.D.3 & 5 of this Order:

 

(3) "Replaces" means "to put something new in the place of' according to the online version of Meriam-Webster Dictionary. In terms of a net metering facility, the key equipment that allows net metering to happen is the inverter(s) and the key number is the alternating current ("AC") output of the inverter(s) (i.e., the nameplate capacity). Repairs, updates, and upgrades to portions of the net metering facility that do not increase the nameplate capacity of the net metering facility will not be considered to be replacing the net metering facility. 2 The amount of nameplate capacity that will be considered to be participating in the net metering tariff is the amount of nameplate capacity that is in place prior to the deadlines in Indiana Code §§ 8-1-40-13 [June 30, 2022] and 8-1-40-14 [December 31, 2017]. 

 

(5) "Nameplate capacity" means the full-load continuous rating of a generator under specified conditions as designated by the manufacturer. For an inverter-based net metering facility, name plate capacity means the aggregate output rating of all inverters in the facility, measured in kW AC. 

 

    That said, I would agree that, due to the large "surge" of interconnection applications that were filed on or shortly before June 30, 2022 and DEI delays in processing those applications after June 30, 2022, DEI DID agree (and the Commission did allow) the affected customers with timely-filed interconnection applications to be covered by the DEI Net Metering Tariff effective on June 30, 2022 rather than its EDG Tariff which became effective July 1, 2022.  BUT, to my knowledge, DEI never agreed to and the IURC never approved exceptions to the amount of capacity of a Net Metering installation to be increased beyond the inverter capacity listed in the timely-filed (but later approved) interconnection application.  See attached Level 1 Interconnection Application, effective July 30, 2020, esp. this line:

 

 

    Please do advise if you have follow up questions, comments or additional documentation for your contention to share.

 

    Thanks!

 

    Mike

 

[Note 1:  The DEI Level 1 Interconnection Application which became effective on February 27, 2025 now includes an Appendix requiring additional information regarding replacements or additions to existing solar installations, which expressly differentiates between additional inverter capacity and additional panel capacity.  See attachment.]

 

[Note 2:   As grandfathered DEI Net Metering customers, my wife and I have certainly retained our copy of our approved 2016 Interconnection Agreement (in which we did substantially increase our inverter capacity when we installed solar panels on the roof of our home to supplement those installed in 2010 on the roof of our garage) to document beyond doubt that increase took place before and not after December 31, 2017 so that all of our capacity is grandfathered through 2047.] 

    

Michael A. Mullett

723 Lafayette Avenue

Columbus, IN 47201

Phone: (812) 350-0707

E-Mail: mulle...@aol.com 

 

In a message dated 1/17/2026 9:57:38 PM US Eastern Standard Time, ajo...@gmail.com writes:

 

Hi all,

 

Just wanted to share on the grandfathering of net metering front.

 

At the end of net metering eligibility during 2022, when my solar system went in, Duke made guarantees that they would honor grandfathering status no matter the type or extent of change to a person's solar system. I was very clear and used numerous examples. I was told that even if someone installed a minimal, 3.8 kW AC system and came back and added 11.4 kW AC of additional capacity, that this would not change the net metering status. I was very surprised, I would guess that most IOUs are not thinking this way, but on Duke there is a decent chance that any expansion might be approved without losing net metering. Just obviously check with them before you have large financial commitments to a project.

 

Best,

 

Alex Jorck (he/him)

ajo...@gmail.com | 812.371.6197

Commissioner, Bloomington Commission on Sustainability

 

From: 'Mike Mullett' via SIREN Public Discussion Forum <fo...@sirensolar.org>

[Myers, Vicky J]

Erin: Directions for unsubscribing from the Siren list are at the bottom of each message.  I have removed the text of the multiple messages and left the footer so that you can find it more easily.  I also highlighted the directions for unsubscribing in bright yellow below.  Please see the footer to get the information that you need in order to remove yourself.

Best, Vicky

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To: Alex Jorck <ajo...@gmail.com>
Cc: Shawn Holsapple <sh...@hoosier-solutions.com>; Mike Mullett <mulle...@aol.com>; bmo...@mortonsolar.com <bmo...@mortonsolar.com>; rwwils...@gmail.com <rwwils...@gmail.com>; jimshackelford3 <jimshac...@gmail.com>; mhirs...@gmail.com <mhirs...@gmail.com>; dar...@sirensolar.org <dar...@sirensolar.org>; fo...@sirensolar.org <fo...@sirensolar.org>
Subject: [External] Re: [SIREN Discussion Forum] Heat pump experience, good or bad

 

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Can we please remove me from this email list. 

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[Mike Mullett]

Alex, All -

 

    While it was strongly (and justifiably) recommended to me for another reason (VPPs), the latest episode of the Volts Webinar with David Roberts has an interesting side discussion regarding his personal experience with electric heat pumps with the guest presenter, Seth Fraser-Thompson, CEO of Energy Hub.  

 

    See https://www.volts.wtf/p/lets-dig-a-little-deeper-into-virtual (at 1:06 through 1:07).

 

    BUT, whatever your thoughts about electric heat pumps, please do listen to the rest of the webinar because VPPs should be and are very likely to be of particular interest to folks on the SIREN list-serve -- especially now. . . .

 

    Mike

Michael A. Mullett

723 Lafayette Avenue

Columbus, IN 47201

Phone: (812) 350-0707

E-Mail: mulle...@aol.com 

 

In a message dated 1/17/2026 9:57:38 PM US Eastern Standard Time, ajo...@gmail.com writes:

 

Hi all,

 

Just wanted to share on the grandfathering of net metering front.

 

At the end of net metering eligibility during 2022, when my solar system went in, Duke made guarantees that they would honor grandfathering status no matter the type or extent of change to a person's solar system. I was very clear and used numerous examples. I was told that even if someone installed a minimal, 3.8 kW AC system and came back and added 11.4 kW AC of additional capacity, that this would not change the net metering status. I was very surprised, I would guess that most IOUs are not thinking this way, but on Duke there is a decent chance that any expansion might be approved without losing net metering. Just obviously check with them before you have large financial commitments to a project.

 

Best,

 

Alex Jorck (he/him)

ajo...@gmail.com | 812.371.6197

Commissioner, Bloomington Commission on Sustainability

 

From: 'Mike Mullett' via SIREN Public Discussion Forum <fo...@sirensolar.org>