I'm trying to find the actual efficiency rating of our Suburban RV furnace... but so far have found no published specifications.Anyone have the real world efficiency rating of the typical RV LP furnace... I'm guessing 70 to 75%.I'm trying to compare the cost of electric heat at 13 cents per kilowatt hour vs LP at $2.79/gallon and assuming 75% efficiency.Using the link below... LP @ 2.79/gal vs 13 cents per kW hour... its less expensive to heat with electricity.http://www.maxmcarter.com/fuels/fuelscalc.htmlElectric vs Fuels - Comparison ResultElectric:Electric rate (per kilowatt-hour) = 0.130Cost of heat (per 100,000 BTU) = 3.81Fuel:Propane cost per gallon = 2.79Burner efficiency factor = 75%Cost of heat (per 100,000 BTU) = 4.03

You are high. Try 60-65 percent efficiency.

As Sidecar mentions, they are not built for efficiency, but neither is most RVs.Your in Alaska, I hope you are not planning to live in a RV for the winter..You have at the most R3 in the floor and the walls R6 and roof R11 in the center, single pane windows with nice cold aluminum frames..You have not much more than a oversized wooden fishing hut on wheels.You are going to use twice as much energy whether it is propane or electric than what you think you might.Yeah, you ARE going to be cold and broke..I would be looking at super insulating before trying to calculate the cheapest heat.

Gdetrailer wrote:As Sidecar mentions, they are not built for efficiency, but neither is most RVs.Your in Alaska, I hope you are not planning to live in a RV for the winter..You have at the most R3 in the floor and the walls R6 and roof R11 in the center, single pane windows with nice cold aluminum frames..You have not much more than a oversized wooden fishing hut on wheels.You are going to use twice as much energy whether it is propane or electric than what you think you might.Yeah, you ARE going to be cold and broke..I would be looking at super insulating before trying to calculate the cheapest heat.Nope not in Alaska... we are in Utah right now. ( Our 5th wheel has never been in AK... we store it in the lower 48.)I'm cheap and just trying to save a buck.

60% is more likely for efficiency. I did some searching a few years ago and best info I could find was mfg data indicating effiencies in the 60% range. could even be less than 60%.more like what a home furnace was 40 years ago. even a 80% efficiency home furnace has significant improvements in the heater box, air intake, exhaust to even get to 80% efficiency. anything above 80% requires having a second heat exchanger in the exhaust and capturing the latent heat in the water produced. E.G. a condensing furnace.

SidecarFlip wrote:You are high. Try 60-65 percent efficiency.Actually closer to 80%, our 30,000 btu Surban is 30,000 I put, 27,600 btu output. We do have a Cheap Heat add on unit and on a 50 amp 240 volt it is 5,000 watts about 17,060 btu,’and heats our 32’ three season Copper Canyon very well.

RV LP Furnace Efficiency? | Good Sam Community

seaeagle2
Explorer
Feb 26, 2018
if you guys can wait til Friday, I'll use my combustion analyzer and give you an exact answer for my specific furnace.
S_Davis
Explorer
Feb 25, 2018
ktmrfs wrote:
S Davis wrote:
ktmrfs wrote:
JaxDad wrote:
beemerphile1 wrote:
sidney wrote:
...Anyone have the real world efficiency rating of the typical RV LP furnace. I'm guessing 70 to 75%....

Why guess? Do the math. Look at the label on YOUR furnace. Divide the output BTU by the input BTU.

That only gives you the combustion efficiency, it does not account for the heat exchangers efficiency.

A typical RV furnace is only ~70% efficient.

I disagree. stated BTU output on a furnace is the BTU output through the heat exchanger. E.G. the BTU of the air coming out of the heat exchanger. BTU input is the BTU of propane or NG going into the burner.

combustion efficiency on a gas furnace is very close to 100%, like most any external combustion vapor fueled appliance.

Well not exactly, when figuring combustion efficiency you have to factor in everything that supports combustion in that appliance. Including heat of exhaust gas. If anyone is close to Mount Vernon WA I have a combustion analyzer I can test your furnace with and give you exact numbers.

If one looks at the BTU of the input gas source and then measures the TOTAL BTU output after combustion, it will be very near 100% for a properly adjust external combustion source. That calculation will include the BTU in the heated exhaust gas and the heat of vaporization of the water as a byproduct of combustion as well as the heat going into the heat exchanger. Basic thermodynamics.

Now, when one looks at the heating efficiency, the input BTU of the fuel and the BTU of the heating output, that's another story, usually well under 100%. 95% for a condensing furnace.

But we are talking about the combustion efficiency of a furnace not a open flame, so you need to account for the loss out the flue and any other losses not going into the conditioned space to figure efficiency.
ktmrfs
Explorer II
Feb 25, 2018
S Davis wrote:
ktmrfs wrote:
JaxDad wrote:
beemerphile1 wrote:
sidney wrote:
...Anyone have the real world efficiency rating of the typical RV LP furnace. I'm guessing 70 to 75%....

Why guess? Do the math. Look at the label on YOUR furnace. Divide the output BTU by the input BTU.

That only gives you the combustion efficiency, it does not account for the heat exchangers efficiency.

A typical RV furnace is only ~70% efficient.

I disagree. stated BTU output on a furnace is the BTU output through the heat exchanger. E.G. the BTU of the air coming out of the heat exchanger. BTU input is the BTU of propane or NG going into the burner.

combustion efficiency on a gas furnace is very close to 100%, like most any external combustion vapor fueled appliance.

Well not exactly, when figuring combustion efficiency you have to factor in everything that supports combustion in that appliance. Including heat of exhaust gas. If anyone is close to Mount Vernon WA I have a combustion analyzer I can test your furnace with and give you exact numbers.

If one looks at the BTU of the input gas source and then measures the TOTAL BTU output after combustion, it will be very near 100% for a properly adjust external combustion source. That calculation will include the BTU in the heated exhaust gas and the heat of vaporization of the water as a byproduct of combustion as well as the heat going into the heat exchanger. Basic thermodynamics.

Now, when one looks at the heating efficiency, the input BTU of the fuel and the BTU of the heating output, that's another story, usually well under 100%. 95% for a condensing furnace.
Gdetrailer
Explorer III
Feb 24, 2018
spoon059 wrote:
Gdetrailer wrote:
I know from personal experience that electric resistive heating is much more expensive than propane or natural gas...

Years ago, my DWs uncle had a mobile home that was heated exclusively with an electric resistive furnace. His AVERAGE electric bill was over $500 per month and that was on a "payment plan" deal..

DWs parents had a mobile home 50ft away and used heating oil, their electric bill was $100 per month and the heating oil cost $125 per month on the yearly payment plan...

Have a Cousin with heat pump system for their home, they average 5-8 yrs on a heat pump then it fails...

A lot of "Absolutes" in your statement...
Heating costs depends upon efficiency and fuel costs. An ultra efficient electric heater can be a lot cheaper than an inefficient gas heater. Gas, depending upon availability, can be more expensive than electricity. Natural gas, piped to your house, is usually cheaper than propane, which is trucked to a dealer and then either delivered or picked up by the end user.

The uncle likely paid a little more per month for 3 months out of the year, whereas the parents paid $125/month for the entire year. Based upon the numbers you quoted, it is impossible to determine that the electric heat was more expensive because the electricity is used to power more than the heater. Even still, we don't know the efficiency of the heaters involved, nor the level of insulation of the mobile homes in the scenario.

For direct comparison, when we bought our house we had an oil boiler for heat. First winter we spent $3000 in oil to keep warm over the 4 months December through March. The following spring we had a heat pump installed in our house that replaced an old and inefficient air conditioner. Same house, same insulation, same everything. Electric bills raised by about $120 a month in those same 4 months the next year. Total heating cost was estimated to be $480. A little over 2 years worth of winters would have been our breakeven point... but since the AC was old and the heat pump was much more efficient at cooling, we figure we broke even long before the 2nd year.

Lastly, the "average" life expectancy of a heat pump is closer to 15 years, not 5-8 years.

Not my words, it is THE GOVERNMENTS WORDS below..

HERE

"Electric resistance heating is 100% energy efficient in the sense that all the incoming electric energy is converted to heat. However, most electricity is produced from coal, gas, or oil generators that convert only about 30% of the fuel's energy into electricity. Because of electricity generation and transmission losses, electric heat is often more expensive than heat produced in homes or businesses that use combustion appliances, such as natural gas, propane, and oil furnaces.

If electricity is the only choice, heat pumps are preferable in most climates, as they easily cut electricity use by 50% when compared with electric resistance heating. The exception is in dry climates with either hot or mixed (hot and cold) temperatures (these climates are found in the non-coastal, non-mountainous part of California; the southern tip of Nevada; the southwest corner of Utah; southern and western Arizona; southern and eastern New Mexico; the southeast corner of Colorado; and western Texas). For these dry climates, there are so few heating days that the high cost of heating is not economically significant."

My Cousins live in a climate that deals with LONG PERIODS of high temps (100F-110F) and high humidity for WEEKS to even a month or two during summer and winter down to the upper 30F..

That really means their heatpump must work 24/7/365 unlike milder more temperate areas.

They are now on their 4th Heatpump since they built their house back in the 1970s..

Contrast that to my parents home where they are only on their second gas furnace since they built theirs in the 1950s..

I will take NG any day..
Harvey51
Explorer
Feb 24, 2018
Gas heaters are inefficient because much of the heat is lost through the exhaust. This includes radiant heat gas heaters - if it burns gas it has to have an exhaust or it soon makes the air poisonous. Construction site heaters can keep the air reasonably safe by bringing a lot of fresh cold air in, heating it, and then exhausting it.
S_Davis
Explorer
Feb 18, 2018
ktmrfs wrote:
JaxDad wrote:
beemerphile1 wrote:
sidney wrote:
...Anyone have the real world efficiency rating of the typical RV LP furnace. I'm guessing 70 to 75%....

Why guess? Do the math. Look at the label on YOUR furnace. Divide the output BTU by the input BTU.

That only gives you the combustion efficiency, it does not account for the heat exchangers efficiency.

A typical RV furnace is only ~70% efficient.

I disagree. stated BTU output on a furnace is the BTU output through the heat exchanger. E.G. the BTU of the air coming out of the heat exchanger. BTU input is the BTU of propane or NG going into the burner.

combustion efficiency on a gas furnace is very close to 100%, like most any external combustion vapor fueled appliance.

Well not exactly, when figuring combustion efficiency you have to factor in everything that supports combustion in that appliance. Including heat of exhaust gas. If anyone is close to Mount Vernon WA I have a combustion analyzer I can test your furnace with and give you exact numbers.
ktmrfs
Explorer II
Feb 18, 2018
JaxDad wrote:
beemerphile1 wrote:
sidney wrote:
...Anyone have the real world efficiency rating of the typical RV LP furnace. I'm guessing 70 to 75%....

Why guess? Do the math. Look at the label on YOUR furnace. Divide the output BTU by the input BTU.

That only gives you the combustion efficiency, it does not account for the heat exchangers efficiency.

A typical RV furnace is only ~70% efficient.

I disagree. stated BTU output on a furnace is the BTU output through the heat exchanger. E.G. the BTU of the air coming out of the heat exchanger. BTU input is the BTU of propane or NG going into the burner.

combustion efficiency on a gas furnace is very close to 100%, like most any external combustion vapor fueled appliance.
SidecarFlip
Explorer III
Feb 18, 2018
If someone could post a link for a condensing furnace for RV use, I'd like to see it
seaeagle2
Explorer
Feb 18, 2018
One more problem with high efficiency condensing furnaces is the condensate has to drain or the furnace rusts out from the inside, you'd need to have the factory level the furnace, then you'd have to correctly level rv so it would drain....
JaxDad
Explorer III
Feb 18, 2018
beemerphile1 wrote:
sidney wrote:
...Anyone have the real world efficiency rating of the typical RV LP furnace. I'm guessing 70 to 75%....

Why guess? Do the math. Look at the label on YOUR furnace. Divide the output BTU by the input BTU.

That only gives you the combustion efficiency, it does not account for the heat exchangers efficiency.

A typical RV furnace is only ~70% efficient.