Cheaper to burn oil than run electric heat pump -)

[zƬesla]

I'm in a cold part of the country. Our highs this past week has been in the 20Fs. Looking over the state's latest energy fuel prices (Jan 2024), it is showing:

Fuel Oil (#2) Current Average Price is $4.08 / Gallon
Btu 138,500
Conversion Efficiency 0.8
$/MBTU $36.80

Electricity Heat Pump Current Average Price is $0.32 / kwh
Btu 3,412
Conversion Efficiency 2.5
$/MBTU $38.10

So, in $/MBTU terms, it is cheaper for me to run the oil-fired boiler than my heat pump mini-splits!? And we get more even heat from the forced hot water baseboards than the mini-splits.

Of course that doesn't include the savings from solar generation. With the current cold snap, we're using ~120kWh/day (mostly for the mini-splits and without the dryer running). On those rare sunny days, we currently generate about 40kWh.

 

[LoudMusic]

Heat pumps are great so long as the outside temperatures are good. I'm sure there are plenty of discussions on the internet about how low the temps can be for heat pumps to remain economically efficient.

 

[RKCRLR]

I have a dual fuel system (heat pump/propane furnace). Currently I'm a net solar producer and net effective metering so it is cheaper for me to run my heat pump using the solar I "banked" during the summer even when it is cold out than it is to run the furnace. However the rules are changing in California and it is possible that it will become more cost effective to run the furnace in cold temperature conditions.

 

[essaunders]

Are you really paying $.32/kwh? I'm in NH and I think I'm at $.228/kwh right now.. and expect it to got down again next month.

I ran the math with $.228/khw and get ~27 $/MBTU . That's about the same as pellets - so i'm just running both.

 

[Will792]

I also question current electricity price used in calculations. I am in CT (EverSource) and electricity price went down from 30+ to around 26 cents per KWh last summer.

 

[yblaser]

I am getting a heat pump installed next week in coastal Southern California and have been trying to do the fuel cost comparison relative to my old 80% efficiency natural gas furnace. It seems close to break even with gas at $1.50/therm, although last year at this time it was $3-4/therm, and off peak energy at $0.22/kWh. However, I don't know what a good assumption for the COP of the heat pump (HSPF2 of 9-10) is given the mild climate with lows in the winter typically in the low to mid 50s with a handful of days in the low 40s.

That said, it is mostly an academic exercise since this year without the heat pump I'll be a net producer of close to 1 MWh and have enough NEM credits that I could use 2-3 MWh before paying retail price for the electricity. Well, at least for the next 18 years before I lose NEM2.

 

[tomuo]

Last year SoCal gas central heating users probably got whiplash from the therm pricing changes from production/pipeline shortages.

If I had a choice, I'd probably do multiple mini-splits instead of one larger heat pump for the central system, would give me finer control over where and when the house is heated/cooled.

 

[offandonagain]

I am getting a heat pump installed next week in coastal Southern California and have been trying to do the fuel cost comparison relative to my old 80% efficiency natural gas furnace. It seems close to break even with gas at $1.50/therm, although last year at this time it was $3-4/therm, and off peak energy at $0.22/kWh. However, I don't know what a good assumption for the COP of the heat pump (HSPF2 of 9-10) is given the mild climate with lows in the winter typically in the low to mid 50s with a handful of days in the low 40s.

HSPF2 is the new metric with stricter requirements, 35F test temperature. HSPF2:10 / 0.89 => HSPF:11.2 * 0.293 => COP:3.2
So COP ~3.2 at 35F, and it will go up with higher temperatures. Your heat pump manufacturer might publish efficiencies at varying temperatures, but just for reference: one of the Mitsubishi heat pump's COP ranges from 2.85 at 17F to 3.95 at 47F.

Heat pumps are very efficient in mild climate, it's only in cases like the OP's (low temperature, high electricity prices) that they start approaching burning oil.

 

[ATPMSD]

relative to my old 80% efficiency natural gas furnace

I suggest you should not be comparing an old gas furnace (which is likely no where near the 80% it used to be) to a new heat pump. Modern gas furnaces can achieve 90%+ efficiency. Also, you should consider which is likely to go up in the coming years, gas or electric rates.

 

[yblaser]

HSPF2 is the new metric with stricter requirements, 35F test temperature. HSPF2:10 / 0.89 => HSPF:11.2 * 0.293 => COP:3.2
So COP ~3.2 at 35F, and it will go up with higher temperatures. Your heat pump manufacturer might publish efficiencies at varying temperatures, but just for reference: one of the Mitsubishi heat pump's COP ranges from 2.85 at 17F to 3.95 at 47F.

Heat pumps are very efficient in mild climate, it's only in cases like the OP's (low temperature, high electricity prices) that they start approaching burning oil.

Thanks. I assumed the conversion from HSPF to COP yielded an average COP over the season given some assumed climate and didn't realize it would yield a COP at a specific temperature. That helps.

 

[zƬesla]

Are you really paying $.32/kwh? I'm in NH and I think I'm at $.228/kwh right now.. and expect it to got down again next month.

That was the tongue-in-cheek part of the the title. Like you, my current Eversource rate is $.2282. My most recent bill shows ~2.5MWh used in the last 33 days.

New Hampshire does not have 1:1 NEM, so from what I banked over the summer, I have <$100 credit left. My total electricity cost for the past 12 months is around $500, not including SREC, which halves that total. It was also a low production year by 0.7-2M compared to the prior two years.

We replaced one of our 2 outdoor heat pump units last Spring. The old one was acting up over winter and I had to occasionally shut it off for several days. So far this winter, the new is working although it hasn't kept up as well and the house is slightly chilly when it gets below freezing. We are yet to use oil for heating though, so I'll be curious what the oil savings at season end looks like.

 

[ATPMSD]

the new is working although it hasn't kept up as well and the house is slightly chilly when it gets below freezing

Hmm. Curious.

Heat pumps often have a radiant heating element downstream of the heat pump’s air exchange unit, which comes on when the heat pump is not up to the job (thermostats are 2-stage devices). I had a heat pump where at 23-degrees the radiant heater was actually more efficient than running the heat pump. If the heat pump was not maintaining the set temperature the thermostat would call for 2nd stage heat and the radiant heater would supplement. At and below 23-degrees the heat pump would turn off since it was just wasting energy.

Is this similar to what you have?

 

[Xenoilphobe]

I installed five LG mini-splits with SEER2 27 and HSPF2 of 15.5 and EER2 of 15.8 (they had better specs last year with the old SEER 1 standards) at our Beachhouse here in Virginia, and we saw a massive drop over our old Central AC unit (circa 1994) 10 SEER (I think, it might have been 9 SEER) and an oil burner that was using $800 a season in heating oil. Also went with a HPWH which only uses about $100 in power a year verses $500 a year with the old electric resistance water heater we had before.

Still have a pellet stove just in case the power goes out, I can plug it into our car and run the auger and blower and heat the whole house.

We noticed the following:

1. Less dust in house, the air ducts were sucking in crap from the crawl space and the oil was leaving a light coating of dust, we sealed them off.
2. January electric bill dropped from $197 per month + $150M in oil to only $99 in electric for heat with mini-splits and to heat water with the HPWC.
3. House in a lot quieter and I can control and monitor the systems remotely/individually (including the water heater)
4. I have 5 completely independent systems if one or two fail, it's not an issue. I also left the electric baseboard heaters in for backup (circuit is shut off)
5. I did all the work myself, saving the labor costs. Hardest part was running line sets and triple vacuuming the lines.
6. I bought all the tools needed to install and can now maintain my own systems.
7. In summer the savings are even more extreme, as we usually have a house full of guests using hot water and the hot tub and more dryer cycles (beach towels and generally more laundry and a window shaker unit I added increasing the electric load in the garage (15 SEER also LG), our peak usage is August, originally it was $385 (before I rebuilt the hot tub heater and added another AC unit in garage) in electric in August and now it's about $237 with better humidity control. The house is 2200 SF was built in 1920 and has no insulation in the crawl space or floor. It does have cheap double pane windows and some insulation in the attic and walls. I plan to spray foam it this summer.... this should have a huge impact and I may have to move a couple of the mini splits to our high bay garage so they don't "short cycle" the mini splits. I highly recommend these LG systems if you live in a milder climate like coastal Virginia. If you are North of the Mason Dixon Line (39°43'19.521" north latitude) make sure you have supplemental heating (pellet, resistant heaters, firewood) for those ten or so days that drop below 5F.

 

[Xenoilphobe]

Hmm. Curious.

Heat pumps often have a radiant heating element downstream of the heat pump’s air exchange unit, which comes on when the heat pump is not up to the job (thermostats are 2-stage devices). I had a heat pump where at 23-degrees the radiant heater was actually more efficient than running the heat pump. If the heat pump was not maintaining the set temperature the thermostat would call for 2nd stage heat and the radiant heater would supplement. At and below 23-degrees the heat pump would turn off since it was just wasting energy.

Is this similar to what you have?

No,l think it just increases the variable speed inverter to generate more heat, I have the LGRED system on my mini splits that will work down to -13 degrees Fahrenheit but realistically work optimally to 5 degrees Fahrenheit, then performance degrades losing BTU output below 5 degrees. Also the price on these just dropped to $1500 for a 9K BTU unit, I paid $1700 per unit for the 12K BTU units one in a North facing, family room 27' x 15' x 15' ceiling and one in a open floor plan Kitchen/dining room/formal living room and $1500 for the 3 9K BTU units I bought for the bedrooms.

Here is the water heater, expensive but worth it. This is all in prep for a solar project next.

WHAT IS LGRED° HEAT TECHNOLOGY?
Products featuring LGRED° heat (Reliable to Extreme Degrees) boast superior performance under challenging conditions. Be toasty warm even in the coldest winter months, when traditional units are unable to keep up with with demand. Expect 100% heating capacity down to 5° F and continuous heating operation, even 70% efficient when it’s -13° F outside.

 

[Skavatar]

I dabble in crude oil and natgas stocks, crude oil and natgas inventories have been up. We have had record oil and gas production this past year. For the past few months the US has been the #1 producer of crude oil world wide. Natgas inventories are 11% above the 5 yr average.

Things are relatively calm for oil&gas right now. It could change considerably in a few weeks or a few months. Its good to have more than one source of heating/cooling.

 

[Xenoilphobe]

I agree, I used to work for Dynergy, (left after ENRON screwed the whole trading market)I essentially have 3 sources at the beach house to heat with: pellets, electric baseboard and Electric heat pump. if all else fails I can fire up the gas genset and power the whole place using 87 octane.

PACE Plan:
Primary: Electric Heat Pump (5 X redundancy)
Alternate: Pellets
Contingency: Electric Baseboard
Emergency: GenSet to drive any of the above with Solar soon to follow

My house in NOVA, I have a similar plan; variable speed heat pumps (Bryant Evolution Extreme 24 SEER2 22 / HSPF2 X 10.5) X 2 (2 ton upstairs/3 ton downstairs)with natural gas furnace for supplemental heat below 21 degrees and gas hot water and cooking, Wood-stove with blower, Plus another gen set (Multi-fuel 87 Octane and Nat Gas) and 16 KwH of solar grid tied with micro inverters. 80% of load. 20% from grid.

Farmhouse has a wood stove (with access to 170 acres of hardwoods) baseboard, heat pump with propane furnace supplemental. But its completely net zero, with its own well/septic/ and electric (another gen set there), solar 12 KwH with backup power that is grid tied... I love that place, wife hates it...

I also priced out a MIrco-CHP vs Solar... still too pricey.... but the waste heat would have been great for my pool/hot tub/ hot water for house

https://understandingchp.com/files/2017/01/CT-Luxury-Home-Case-Study.pdf

6-8-rules-of-thumb-for-chp-engineering-and-installation-costs

 

[zƬesla]

Hmm. Curious.

Heat pumps often have a radiant heating element downstream of the heat pump’s air exchange unit, which comes on when the heat pump is not up to the job (thermostats are 2-stage devices). I had a heat pump where at 23-degrees the radiant heater was actually more efficient than running the heat pump. If the heat pump was not maintaining the set temperature the thermostat would call for 2nd stage heat and the radiant heater would supplement. At and below 23-degrees the heat pump would turn off since it was just wasting energy.

Is this similar to what you have?

The new outdoor unit is a Mitsubishi HyperHeat (MXZ-3C30NA?) rated down to -15F, and it has kept running thus far. The old Mitsubishi was rated to around 5F and wouldn't do much at around 15-20F.

Here's the spec on the new unit:

Waiting on tech to come and take a look to see if there's a leak somewhere.

 

[zƬesla]

6. I bought all the tools needed to install and can now maintain my own systems.

What are you doing for maintenance? What's the cleaning routine?

 

[CrazyRabbit]

I dabble in crude oil and natgas stocks, crude oil and natgas inventories have been up. We have had record oil and gas production this past year. For the past few months the US has been the #1 producer of crude oil world wide. Natgas inventories are 11% above the 5 yr average.

Things are relatively calm for oil&gas right now. It could change considerably in a few weeks or a few months. Its good to have more than one source of heating/cooling.

Have you been thru Midland and Odesa lately? I-20 is congested.

 

[Skavatar]

Have you been thru Midland and Odesa lately? I-20 is congested.

no, furthest West I've driven is San Antonio. went took a vacation in June to DFW.