Space heaters vs Propane furnace, which is cheaper to run?

[Emptynester]

We just got a shocker of an electric bill and the electric company is blaming our spike in the needed electricity to run our propane furnace. Which is cheaper, running an electric space heater as our only source of heat or running our propane heater on a thermostat to come on and off as needed? We are living full time in a 29' Keystone Springdale toy hauler.

Thank you to anyone that can help with a comparison!!

[turbopilot51]

Originally Posted by Emptynester

We just got a shocker of an electric bill and the electric company is blaming our spike in the needed electricity to run our propane furnace. Which is cheaper, running an electric space heater as our only source of heat or running our propane heater on a thermostat to come on and off as needed? We are living full time in a 29' Keystone Springdale toy hauler.

Thank you to anyone that can help with a comparison!!

Are you talking about the furnace in the rv? That furnace uses 12volts from your converter plus propane.

[Emptynester]

Yes, I don't understand all the workings of our travel trailer, but even I question the power use of our propane furnace running that much. We are hooked up to 30amp power on our lot, so we aren't running on just batteries.

[crash]

Sounds like they are trying to stick it to you on that one

[JRTJH]

The electricity to convert AC to DC to run the fan on the furnace and to charge the battery shouldn't be much more than 10 or 12 dollars a month. If there were any "spike" in electricity use, I'd expect it to be from plugging in a 120VAC space heater or another "big energy user" like your air conditioner.

The electricity consumption by turning on the 12 VDC fan motor shouldn't cause much more than maybe a 3 or 4 dollar increase over your normal consumption. If the electric company is telling you there's a "dramatic increase" in power consumption using a 1/8 HP DC motor, you need to have them check the meter for accuracy.

Now, that said, what some electric co-ops and even commercial electricity providers do (if they don't have digital meters) is read the meters every 3 months and use the average of the last reading as the monthly charge. Next time they read the meter, they bill for any "under estimated" use and credit for any "over charged" use. You may have gotten caught in the summer A/C season with an "estimated use" average being billed for the spring when you were using much less energy.

I'd definitely look into what happened.

[Emptynester]

I assume when we are plugged into the 30amp service the furnace runs directly off that and not thru the batteries or converter? I ran the propane furnace, watched the power meter on the pole run, then shut it off and ran a space heater and again watched the power meter on the pole, and found not much difference in the speed the meter was running. Perhaps I've answered my own question in just watching the meter while running each source of heat.

[Emptynester]

John,

Thank you for your longer explanation. Our power company, Puget Sound Energy, doesn't use the 3 month reading-average for billing. The read the meters every month and bill every month. We had been using the A/C in our trailer over the summer and into Sept. And our electric bill was $88 for one month. Then we turned on our propane furnace and it jumped to $141. That caught my attention!! So I decided to post-ask which source of heat full-timers found to be cheaper to run with electricity (not counting the cost of propane in the mix).

[JRTJH]

You made the statement that you assume when plugged into 30 amp 120 VAC that the furnace runs directly off the trailer without going through the battery or converter. That is not correct. EVERY 12 volt appliance in your RV goes through the converter if plugged into 120VAC shore power. The only time that isn't true is when you're drawing more DC power than the converter can provide, then the system will draw from the battery as a "backup" source of DC power.

NONE of the 12VDC components in your RV have the capability of running off 120VAC power (on their own) NONE of them can "make" their own 12VDC power and all must rely on either the battery or the converter. When you're plugged into shore power, the converter "under normal situations" supplies all of the DC power needed.

In my opinion, there is no way the fan on the furnace used that much electricity. If your bill was 88 with the A/C running, when you run the furnace, the A/C is not on, so it's "one or the other" not both. You would have "theoretically" used $70-90 in electricity with the furnace on and the A/C off. That's virtually impossible.

Now, to answer your question on which is cheaper, 120VAC space heaters or the propane furnace.... They are just about the same cost to operate. With the space heaters, you use a lot of electricity and no propane. With the furnace, you use a lot of propane and a little electricity. Depending on the cost of propane, it may be slighlty higher or lower than using space heaters, but it is most likely pretty close to the same cost.

Heating with electricity in a "mild winter" shouldn't cost any more than cooling with the A/C in a "mild summer"

[Emptynester]

Thank you for helping understand how my trailer actually works. And the more I know, the less I understand how my bill go so high!! I called PSE again, and they are certain the problem is on our end. Guess this is just a case of paying the bill.

[BulletOwner1]

JRTJH, I think you answered it. We're currently camped near Reno and using both the RV furnace and a small portable electric heater and I have wondered which would be cheaper. It does probably depend on the kwh charge and the price of propane. Here we are paying 3.30 for propane, I don't yet know what the elec. charge is. I know I like the little elec heater because its quite but it does eat the KW's.

[JRTJH]

Yes, space heaters do love to gobble electricity, but the furnace also uses a trememdous amount of propane (very inefficiently at that) and produces very little BTU's of heat for the BTU input of propane. At $3.30 a gallon for propane, it wouldn't take long to justify a 200 gallon "pig" to be serviced at "home rates" rather than at convenience store rates. That is, if you're going to be in one place long enough to justify renting the big tank.

To give you an example of how inefficient a propane RV furnace is, just walk outside when it's running and put your hand near the vent stack. You'll see that nearly as much heat is ejected through the vent as is retained within the RV.

If you're anywhere near Carson City, check the price of propane at Tractor Supply. Usually they sell bulk tank refills for $2.49 a gallon. That's where we try to refill our tanks when we travel. It's been a pretty consistent price at TSC for the past 18 months or so.

[BulletOwner1]

Thanks John. We're at Fernley, workcamping for Amazon. Found gas for 3.00 at Fallon but that's the cheapest around here. Amerigas has pretty tight grip in the local area.

[hankaye]

Howdy All;

I agree with JRTJH, about the methods and madness of which works what.
Last Winter I noticed a 'spike' in my electric bill and found that the batteries
had lost all of their juice ...boiled out. Prior to that I had noticed that the
cooling fan for my converter ran as soon as I turned on just one 12 vdc light.
My inattention cost me roughly $250.00 for 2 new 6 volt batteries.
Battery maintenance is something that needs greater than normal attention
during periods of high cycling of the 12 volt system, winter with the heater running.
Don't forget, distilled water only.

hankaye

[OCB]

I don't know the details on your type RV or the cost of the electricity or Propane, so I will give some off hand numbers.
Using 100,000 BTU per gal of Propane (and 8 gal tank, 30#) and a 75% efficency furnance ( that may 10-20% high) you would result in 600,000 of usable heat.
Similiar comparsion would the be the electric resistance heater, 100% efficent, producing 3400 BTU per KWH of electricity or 176.5 KWH to produe the same 600,000 BTU.
Stated earlier in the post, Propane was $3.30 per gal or $26.40 for for the 600,000 BTU of heat from a 30# tank. Compareably that is the same as using $0.15 per KWH so that is a break even.
I buy my propane for less but I suspect my furance to be nearer 60% efficent, so again break even.
Now back to the RV, what are you heating, what was the outside Temperatures and do have have some type of artic protction. Your Propane furance may be heating your underbelly and waste tanks where as the electric space heater only living space thus the floor is colder so the Electric heater(s)may work more or less do to comfort zone. What has been the colder temperatures do you have electric heaters/heat tape connected to the tanks? Lots of factors

Final question How many days did your Electric bill represent, were they both 30 or 31 days. Figure the cost (or KWH) used per day rather than cost month. Last but not least if you can read your meter daily, do that at approx the same time and also write down the temperature and see the effect of temperature on useage per day.
Rather lenghty put I have the same interest in computing cost for my winter stay where freezing temp.

[ocbms]

Another item which could increase the electric usage would be a bad electric element in the water Heater. With a bad element you could still have some hot water.
Option is to switch the electric off on the water heater and use gas. does the problem go away by watching daily usage?
Could also apply to refrigerator but unlikely.