Gas heater running = high electric bill?

yoda888January 14, 2012


Does using a gas furnace (Trane XE 80) to heat the house increase the electricity usage substantially? Is the fan using a lot of power?

Our electric bill has essentially doubled in the past two months (vs. the previous months). We have not added any crazy appliances/toys/electronics in the past two months that would consume large amounts of power.

One thing we have been using is the heater (the gas portion of the bill has doubled as well.)

I'm in CA using PG&E as our utility. They offer the ability to monitor your electricity usage. However, it is not real time (usually delayed by 24-hours so I can't plug/unplug/turn-on/turn-off stuff)

One thing I did notice is that the power usage seems to go up in the AM (when we get up), and up again when we get home in the evening from work. Peaks at around 11pm-12am (going to bed) and then goes back down.

I do turn down the thermostat before bed. So I'm thinking it might be the heater.

Is this normal? This seems crazy to me!


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Is the thermostat in set in the auto or the fan mode. In the auto mode the fan operates only when the furnace calls for heat. In the other mode, the fan run continuously. The fan running all the time will consume much more power.

Have you had usually cold weather? This may explain the additional gas usage. When was the last time the furnace was serviced? You may have other problems.

    Bookmark   January 14, 2012 at 10:00AM
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The thermostat is set on "fan" mode. In this case, it is not constantly running, but rather I am manually overriding the temp for a specific temperature. (Auto mode would require me to read the manual and program the different times/temp, etc.)

However, in this mode, I it works the same as auto. The fan/furnace only kicks in when the furnace turns on. The fan does not stay on constantly even if the furnace is not firing up.

We are having a typical CA winter (sans the rain). The gas usage I'm fine with since I'm using the heater.

What has me perplexed is the additional electricity usage which i'm suspecting is due to the heater. Which is counter-intuitive.

Any other comments/suggestions would be greatly appreciated.


    Bookmark   January 14, 2012 at 11:56AM
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What do you mean by "heater". This is a room electric resistant heater used for spot heating?

You have made an effort to eliminate the possibility of some other malfunctioning electrical appliance in your home?

Fan blower should be set to "auto".

What are your electric and nat gas rates?


    Bookmark   January 15, 2012 at 8:10AM
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Sorry, when I say heater I mean furnace.

Yes, the fan blower is set to "auto"

As far as rates, I need to investigate that.

I guess my main question really is this, "does using the furnace use a lot of electricity?"

My furnace runs on natural gas, but obviously the blower/fan uses electricity. I'm wonder if that is sucking up a lot of power.


    Bookmark   January 15, 2012 at 11:59PM
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While you have a low end 80% eff Trane furnace, to answer the question about the blower, the answer is no.

The blower motor unless malfunctioning could not be the cause of your electric bill doubling.

I have to ask this question and rarely do I receive an answer. How old is your furnace and when was your system last serviced and checked by an HVAC pro?


    Bookmark   January 16, 2012 at 6:20AM
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This would be right around the time of year that PG&E electric bills might double from a few months earlier - combination of higher actual usage plus creeping into higher rate tiers. Ironically most pronounced if household is already fairly efficient in electricity usage, because the additional usage jumps from Tier 1-2 ($0.13/kwh) into Tier 3 ($0.30/kwh), as opposed to heavy users who were already substantially into Tier 3-4.

So for example:
-50% more usage in Dec than October - furnace blower running 3X more, more lighting in AM and PM on shortest days of year, Xmas lights, people staying up for parties and New Years, humidifiers and other devices.
-2.3X more per kwh - PG&E reduced baselines by 10% last year, additional usage pushes into Tier 3.

50% x 230% = 115% of previous bill, in this example.

    Bookmark   January 16, 2012 at 5:54PM
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Hmmm, what wwu123 said makes sense. Just seems kind of crazy that the furnace blower would suck up so much electricity.

In regards to how old the furnace is, I have no clue. It was installed by the previous owner. Based on what I can find, I would guess it's at least 15 years old. I have not had the unit service or checked by an HVAC pro. (What do they do when they service it? Is it like a car where belts/wearable parts are replaced?)

As part of an experiment, I did not turn on the heat at all yesterday. (was 52 degrees inside the house when I woke up this morning! I can do this since my wife is traveling for work and she won't complain to me about the lack of heat in the house.) I'm waiting for our "smart meter" to update PGE so I can check the energy usage for yesterday. If the usage stays flat, then it means the furnace/blower uses an obscene amount of power! If there is a spike, then someone is stealing power from me since there would be nothing turned on that wasn't already on during the day already)

FYI: my peak usage of power was on Saturday 8-10pm at 2.23kWh. (can someone tell me what 1kWh is equivalent to?)


    Bookmark   January 17, 2012 at 7:22PM
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1 kWh is 1000 watts of power consumed over a 1-hour period of time. 1000 watts would be ten 100-watt light bulbs. Or five 200-watt bulbs. Or one 100-watt bulb running for 10 hours is also equivalent consumption.

2.23 kWh 8 PM to 10 PM is 2,230 watts used over a 2-hr period.

Instantaneous power draw (demand) is referenced as KW (without the 'hour' component). An electric water heater (4,500 watts) + a portable space heater (1,500 watts) + a clothes dryer (5,200 watts) all running at the same time would be an instantaneous draw of 11,200 watts, or 11.2 KW. If that load ran for an hour, then 11.2 kWh of power would be consumed.

Power usage is measured in kWh for billing, but there may also be a demand charge involved for whatever is the peak KW draw during the billing period.

    Bookmark   January 17, 2012 at 10:51PM
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