NG or mini spit for efficiency?

[Rod N]

I just moved into a rental house. Around 1,200 sq/ft each floor. 2 floors.
Electric heat, 2 stand alone gas fireplaces and a mini spit.
I keep the electric heat off and the doors closed in the 4 bedrooms I don't use. Keep it on in my bedroom, bathroom and downstairs where I watch TV every night.
On the upper floor what is more efficient? The gas fireplace or the mini spit to heat the rest of the upstairs?

 

[whateg01]

A heat pump is more efficient as I understand it because it doesn't convert matter into heat. It just moves heat from one place to another. But depending on the cost of gas and electricity where you are, it might still cost less to run gas.

 

[Rod N]

I've been using the heat pump because I heard they were more efficient.
No idea of the cost from hydro to NG.

 

[whateg01]

It's an easier decision for me since I choose between resistance heating or heat pump.

 

[fitter30]

Lp gallon is 91500 btu
Ng therm is 100k btu cubic ft. 1030 btu
Electric 3.41 btu per watt.
Heat pump most are rated at 47° f. The colder it gets most lose btu's output. All have a spec for lowest temp can be from 5°f to -22°f. Need to take pic of the outside and inside units call the manufacturer tech line for that info, ask for btu's at different temps and if they have wattsfor different outside/ inside temps.
Stove Name tag may or maynot have the btu's listed. Is it vent or ventless? Type of fuel?

 

[dcg9381]

I keep the electric heat off and the doors closed in the 4 bedrooms I don't use. Keep it on in my bedroom, bathroom and downstairs where I watch TV every night.
On the upper floor what is more efficient? The gas fireplace or the mini spit to heat the rest of the upstairs?

Someone will be along with the mini-split calculator. But I'd wager decent money that as long as the mini-split is in the "efficient" range with outdoor ambient, that's probably your answer.

I have 5 heat pumps. 3 are traditional HVAC with heat strips. The other two are 17 SEER Daikins. Below 25 degrees, I don't even try to heat with them because they are outside their efficiency range. I switch to propane heat using ventless units... It only happens a few days a year, if that...

 

[HoosierBuddy]

Most Efficient doesn't always mean cheapest to operate.

That direct vent natural gas fireplace, I'm going to assume, is 80% efficient. The heat pump is going to have a COP of maybe, what, 4.5? Depending on the outdoor temperature?

Unless you are paying through the nose for power, I'm going to guess the mini-split is going to be less expensive per output BTU into the heated space for any reasonable outdoor temperature.

In your situation, I'd use the minisplit as primary and supplement with the fireplace for specific situations:

1. So cold outside that heatpump can't keep up.
2. Had the temperature setback, now want to warm it up in a hurry.
3. Power outage

 

[jack stand]

I'm kinda under the impression that those gas stoves/fireplace are more for room "ambiance" than an actual heating source. I'm sure they put off some heat, but how much of it goes right out the chimney?
You're already in, so keep some records on fuel costs and outdoor temperatures leaning on the MS and then with the "fireplace ".
The above post would also be my guess and with enough cold, you're probably going to end up doing this anyway.

 

[Rod N]

Specs on the heat pump.
My guess is both the fireplace and heat pump are cheap models.

 

[Notgrownup]

They now come only from a few sources. I would say the mini split is likely more effecient.

 

[American Locomotive]

I'm guessing the question you're asking is not actually "which one is most efficient" but actually "which one is cheapest to run"?

If that case, "efficiency" doesn't really matter here. What really matters is the cost of your electricity and natural gas. Without knowing the cost of either per unit of fuel, we cannot provide any advice on which you should be using.

 

[ericm]

Here's the famous Maine spread sheet: https://www.efficiencymaine.com/at-home/heating-cost-comparison/
You have to fill in the costs for your area, and likely also adjust the efficiency of the mini split since the sheet's a few years old now.

Usually piped in gas ("natural" is a marketing term) usually costs less than anything else, but not always. Running it in a low efficiency burner will negate that to some extent.

The other factor that's not on the sheet is comfort. Sometimes a point source of heat, like those old wall registers, are terrible at distributing heat through the room and house. Mini splits seem to do ok there.

 

[WisJim]

With minisplits, there's a lot of difference between units in the lowest temp at which they maintain efficiency. The data plate given doesn't tell much about the efficiency specs. Units are available that are good to well below zero degrees F.

 

[danski0224]

On the upper floor what is more efficient? The gas fireplace or the mini spit to heat the rest of the upstairs?

Ultimately, one does not know the answer to this question until some work is done, which 99% of the people on this forum do not want to do.

You need a load calculation.

Then you need equipment performance data at 17º and 47ºF.

Then you need utility costs for electricity and the fossil fuel that is being burned.

Then you put the appropriate information into a economic balance point calculator.

ONLY THEN will you know the actual answer. Anything else is just a guess.

 

[pembol]

That is an easy question to answer - the minisplit is definitely more efficient. But I suspect you are asking which is cheaper to operate - that is harder to answer and we would need to know more details on your utility rates, outdoor temperature and the details of both units.

But if you want a wild **** guess - the minisplit is likely cheaper to operate in all but the coldest weather. The most practical way to run this would probably to have the minisplit on and set to the lowest temperature you want in the house - say 63F or something like that, then just use the fireplace on cold evenings, or any time it is particularly cold out (< 20F or so) to heat above that.

 

[kngelv]

Mini-splits are very efficient but do lose efficiency as it gets colder. In northern climates you need a hyper-heat unit. The regular ones efficiency drops off a cliff below 30 degrees. Below is an example of Mitsubishi 2.5-ton units. They produce a little more than rated at 47 degrees but look how much the non hyper-heat drops as it gets cold. At 5 degrees you have lost over 33% of it's efficiency while the hyper heat is down only about 5%.

James

	MXZ-3C30NA4 Standard	MXZ-3C30NAHZ4 Hyper Heat
47 F	36,000 BTU	36,000 BTU
17 F	21,000 BTU	28,600 BTU
5 F	19,800 BTU	28,600 BTU
-13 F	NA	26,400 BTU

 

[Highbeam]

Mini-splits are very efficient but do lose efficiency as it gets colder. In northern climates you need a hyper-heat unit. The regular ones efficiency drops off a cliff below 30 degrees. Below is an example of Mitsubishi 2.5-ton units. They produce a little more than rated at 47 degrees but look how much the non hyper-heat drops as it gets cold. At 5 degrees you have lost over 33% of it's efficiency while the hyper heat is down only about 5%.

James

	MXZ-3C30NA4 Standard	MXZ-3C30NAHZ4 Hyper Heat
47 F	36,000 BTU	36,000 BTU
17 F	21,000 BTU	28,600 BTU
5 F	19,800 BTU	28,600 BTU
-13 F	NA	26,400 BTU

You don't need a "hyper heat" (brand name thing) unit for northern climates. You just need to choose the equipment with the desired output at whatever temperature you want. That usually means oversizing the heat pump for warmer temperatures.

You seem to be confusing efficiency with output rating. You can actually find the efficiency at the various outside temperatures and it does drop with outside temperature somewhat but it's not directly related to output.

 

[Rod N]

Thanks for the help guys.
You are correct. I should have said the cheapest.
To do all the tests and calibrations would be a lot of work and seeing that I'm renting I could move before they are done. So yes I'm in the 99% as stated above. lol
I have noticed with the cold snap this weekend the mini split is running a lot longer so it is having a harder time keeping up.
I'll monitor this and start using the gas fireplaces as it gets colder outside.

 

[American Locomotive]

Thanks for the help guys.
You are correct. I should have said the cheapest.
To do all the tests and calibrations would be a lot of work and seeing that I'm renting I could move before they are done. So yes I'm in the 99% as stated above. lol
I have noticed with the cold snap this weekend the mini split is running a lot longer so it is having a harder time keeping up.
I'll monitor this and start using the gas fireplaces as it gets colder outside.

You just need to look at your gas and electric bill. Look at the rate per kWh for electricity, and how much you pay per unit of gas (and what units it is)

 

[pcmeiners]

If you wan to compare fuel running costs this spreadsheet has most fuels, rather easy, just compare the individual fuel's cost per million BTUs. of each fuel you use. The fuel costs are national average fuel costs applied at the beginning of this year. If your cost are not close to these you can download this spreadsheet and fill in your numbers. Just search Google for Heat-Calc-Van-D_1-09.xls , it will; download automatically.
Natural gas and standard low cost mini-splits were neck and neck in running fuel costs early this year. Very efficient mini-splits can beat the average NG running costs per million BTUs.

 

[kngelv]

You don't need a "hyper heat" (brand name thing) unit for northern climates. You just need to choose the equipment with the desired output at whatever temperature you want. That usually means oversizing the heat pump for warmer temperatures.

You seem to be confusing efficiency with output rating. You can actually find the efficiency at the various outside temperatures and it does drop with outside temperature somewhat but it's not directly related to output.

I'm not confusing anything. In the above chart the regular 2.5 ton is putting out 19,800 BTU's at 5 degrees while the one rated for higher efficiencey is at 28,600 BTU's. You would need a larger unit to match the same BTU output at the 5 degree temp. Higher efficiency means higher BTU at the same temp. This is a big deal in the cold climates. BTW I actually have a Fujitsu and used the Mitsubishi chart because it was easier to find.