Is it cheaper to heat a whole house using gas or to use an electric space heater for one room?
January 3, 2007 3:49 AM   Subscribe

Will it cost less to run a gas furnace to heat the entire house or to use a space heater to heat one room?

I live in a 4 bedroom house and 3 of my roommates have just moved out. In the meantime, I'd like to save on the bills and I'm thinking of lowering the house temperature down to about 55 and using a space heater just to heat my own room. The electric space heater that I have says 1500 w on the sticker on the bottom and it's the kind that has a fan that blows across electric elements, similar to a hair dryer. However, does anyone know if this is worth doing? Or will I end up breaking even?
posted by perpetualstroll to Home & Garden (16 answers total) 3 users marked this as a favorite
It would likely be helpful if you can give info on what you pay for electricity, what you pay for gas to run the furnace, the size of the house, the size of your room, perhaps some info on whether your room is insulated relative to how the rest of the house is insulated.
How will you meet your hot water needs during the period?
posted by biffa at 4:09 AM on January 3, 2007

Response by poster: Oops, sorry-- the house is currently using a gas furnace and the water heater is gas powered as well. As for the bills, it's about $175 a month for electricity during the winter and about the same for gas. Small house, 1800 sq. feet and my room is poorly insulated relative to the rest of the house with older single pane windows.
posted by perpetualstroll at 4:13 AM on January 3, 2007

There are tons of variables here. I personally have been experimenting with the very thing you're talking about - I turned off the gas convection heater and am heating only a single room with an electric heater. In order to pull this off you really have to be pretty conscientious about keeping the door to the heated room closed, otherwise you lose whatever pitiful heating capacity the space heater can put out. Those things are really only designed to keep a small space warm, they won't work well if the room is large or if you don't keep the door closed.

Also, it depends highly on the cost of your utilities. I noticed on my last bill I paid almost nothing in gas charges but due to the increased electricity usage I was way over the "baseline" amount there. PG&E has variable rates based on percentage of this baseline, so for the baseline amont (284.2 kWh in my case) they charge $0.11430/kWh, for 101%-130% they charge $0.12989 and for 131%-200% of baseline they charge $0.22986/kWh, which is almost twice what the baseline rate is. My total usage was 486 kWh and 116.5 of that was in the highest bracket of 23 cents per kWh, which seems pretty outrageous. So any savings I might have made by letting most of the place stay unheated I probably lost on the higher bracket of electricity rate. On the other hand my gas heater is very inefficient and I don't really use the other rooms that much so I think I still came out ahead compared to what I would have paid if I heated the whole place with gas. I don't know if all utilities do this kind of incremental pricing on electricity but you might want to check first.
posted by Rhomboid at 4:23 AM on January 3, 2007

my room is poorly insulated relative to the rest of the house with older single pane windows

If the other three bedrooms are now empty, could you move to one of them?
posted by orange swan at 5:04 AM on January 3, 2007

Where are you?

The outside temp makes a big difference. If you are north and winter is cold you must ensure that you keep your pipes from freezing. Also heating only your room can make bathroom trips and meal prep very unpleasant.

If you have forced air close all the vents in the unused rooms. Styrofoam insulation helps. Make sure you plug all the drafts you can between both your room and the rest of the house and the rest of the house and outside.

older single pane windows

Get some ghetto wrap! (Plastic for covering drafty windows)

Make sure your space heater is well away from anything flammable as well. I'm generally pretty cautious about running them while asleep.
posted by srboisvert at 5:52 AM on January 3, 2007

I did some research on space heaters last month when I wrote about staying warm for cheap. According to Michael Bluejay's energy guide, using a space heater instead of a furnace is the single best way to save money on energy in a home. As others have noted, though, your best bet is to experiment yourself. Good luck!
posted by jdroth at 6:00 AM on January 3, 2007

A guy I know tried this. Since he described the results in a locked entry, I'll just take the liberty of pasting the whole thing here.

Having Scottish blood and a subsequent fondness for pinching as many pennies as possible I decided to test the idea that for one person living in a house, where I am only in one room at a given time, a small portable space heater would provide a smaller amount of more directed heat than my whole-house electric heatpump system could. My theory was that I would be able to make specific rooms of the house (mostly office, living room, bedroom) "hot spots" while I'm in them, and leave the rest of the house to sink to whatever temperature it would (within reason) and not spend the energy required to maintain them at a higher temperature. The general idea is that over a month of this activity, I should save money.

Two weeks ago I bought an electric ceramic space heater with a digital thermostat and two modes: 1500w and 900w (ok, three modes for the pedantic -- it can be switched off). The thermostat would allow me to set a temperature and the unit would run in high, low, or off depending on conditions.

Now, electricity is measured in Kilowatt-hours, and a kilowatthour (kWh) is the amount of energy it takes to run a thousand watt load for one hour, or a one watt load for a thousand hours, or whatever. It's all pretty precise in that a hundred 60 watt bulbs will consume exactly the same amount of energy in one hour as, say, a thousand watt microwave oven operating for six hours straight. There are minor adjustments here and there but I'm certainly not going to get into them in this post.

Now that we have the math settled, let's look at the costs. For the first 600 kWh of my electric bill every month, I pay approximately 14 cents per kWh. This means that having a 60 watt light on for an hour costs me almost a whole penny. Likewise, running a 1.5kW space heater for an hour costs about 21 cents. I have absolutely NO idea how much power the heat pump takes while running. I believe it may have some inverse relationship to the temperature (inside and outside) and it's difficult to measure the duty cycle of the thing anyway. Yes, I could probably have determined the power consumption over an hour it isn't on vs. an hour it is, but first I'd have to ensure it would stay on for a full hour, and then my analysis wouldn't factor in the energy efficiency of the house or any of the other factors that differentiate empirical numbers from real-life results.

Instead I lived it for two weeks. I set my house thermostat down to 47 degrees, so the pipes wouldn't freeze if it got too cold, and didn't touch it for two weeks, instead moving the space heater to wherever I happened to be and wearing a ridiculous number of layers of clothing. Here in Pennsylvania the average daily temperature was approximately 50 degrees, and the unheated house tended to move between 50 and 60 degrees. Only a couple times that I checked did the internal temperature hit 49, and those were early in the morning when it was about 25-30 degrees outside (according to my thermometers).

How did it work? Super, unless you like being warm or saving money. I spent those two weeks using the space heater on average 8 hours a day. Some days I used it more, other days I used it almost not at all, but that's why I did this experiment over a two week period rather than a single day. Most of the time I didn't even use the digital thermostat and ended up running the thing full blast to try to bring some heat into my life. Despite running in high mode all the time, I was hardly creating any saunas -- the digital readout of current temperature on the space heater rarely crested 65.

At the conclusion of those two weeks I went out and read my electric meter. I was armed with the reading from two weeks ago, which indicated a number of 42355. When reading a meter the actual number doesn't matter. What's important is the difference between two given times, in this case over two weeks the number advanced to 43023. By subtracting these numbers I can determine that the difference is 668, which is 668 kWh, which (oddly enough) is exactly one kWh less than my entire month's electric bill from the month before.

My electric company reports some helpful statistics on my electric bill, things like average daily kWh consumption. For instance, average daily consumption last month was 20.2 kWh/day. Let's see, over two weeks...14 days...carry the one...multiply by i^4...and...sweet Tennyson's tomb, that's 47.7 kWh/day, more than three times last month's daily consumption!

So in review, I spent two weeks being rather cold, getting much better acquainted with a quilted plaid shirt that I got for Christmas ten years ago, and on top of all of that...wasted money?

posted by Faint of Butt at 6:28 AM on January 3, 2007

As others have noted, it depends on many variables. However, that being said, a friend of mine does this in his house. He purchased a number of small ceramic heaters that have removable wireless thermostats. He places the thermostat on the other side of the room and sets it to 69 degrees. The heater then only comes on when it needs to (this is key to his savings). His bill went from $200/month to just under $100/month. YMMV
posted by Spoonman at 6:46 AM on January 3, 2007

One thing we did to help save money was install a programable thermostat in the house. That way our house turns way down at night while we are sleeping and away at work or school and goes up for just a few waking hours to keep us comfortable.
posted by Gooney at 6:49 AM on January 3, 2007

Where I live, in a poorly-insulated house in the energy cheap Pacific Northwest, space heaters are definitely cheaper. In some areas of the country, though, electricity costs considerably more than it does here. I suspect that would make a difference.
posted by croutonsupafreak at 7:05 AM on January 3, 2007

Faint of Butt describes a guy who does exactly the wrong thing with his space heater. You need to pick a room, and use the space heater there and only there. If you keep moving the space heater around the house, you'll end up trying to heat the whole house with it, and you'll never come out ahead.
posted by chrisamiller at 7:38 AM on January 3, 2007

Best answer: I've tried similar games to save on gas money, and I've found the most practical compromise is to run the furnace when you're in the house during the day, and in the evening when you're eating and lounging. Then as you go to bed, turn the thermostat way down and close your bedroom door. Use a space heater (I use an oil-filled electric radiator, because it doesn't strike me as being as likely to start a fire as the exposed-coil ones) to keep the bedroom comfortable. By "comfortable" I mean 'warm enough to not be cold when you're under a heavy comforter.' I set it around 65.

The downside is that going to the bathroom at night or in the morning can be unpleasant, but if you can bear that, it's saved me a little bit.

Nighttime is a good guarantee that you'll be in one room for a long time (unless you're really into sleepwalking), so it makes the most sense to me as a time when you can drop the temperature in the house and spot-heat. During the evening or day though, when you're moving from room to room? Unless your electricity is cheaper per BTU than gas, it doesn't make sense.
posted by Kadin2048 at 10:52 AM on January 3, 2007

You can use both your gas and electric meters to test the options a few days at a time.
posted by Good Brain at 10:53 AM on January 3, 2007

Solution: Forget the space heater, buy a nice down comforter. I did this in the fraternity house one year while I was in college- set the temp to 55 and just got lots and lots of blankets (I was too poor to afford the comforter at the time, but if you can swing it, go for it.)
posted by Doohickie at 10:55 AM on January 3, 2007

I've been doing this in my house this winter. I keep the thermostat no higher than 60, rely on sweaters and blankets during waking hours, and use a space heater and electric blanket to warm the bedroom for a few hours before I go to sleep. So far, I've saved about $50-70 per month on my winter bills. I've heard people say that gas is expensive around here, though, so your mileage may vary. It's definitely worth trying!

I think the key is to keep the heaters off as much as you can. Instead, lean on sweaters, blankets, gloves and a hat, a hot bath/shower before bed, and other "free" warming methods. Also, try to cook with the oven rather than the stovetop in winter. You'll be surprised at how much it warms up the house.
posted by vorfeed at 11:57 AM on January 3, 2007

keep your pipes from freezing

This is critical, obviously, so be cautious..

Many old houses have pipes running in uninsulated outside walls. In addition, a single thermostat isn't very good at regulating temperatures in a whole house, so most houses have spots that are considerably cooler than the thermostat setting. To add a very cool indoor temperature to that mix..

So, make sure to think about where the pipes are, and how they will be effected!
posted by Chuckles at 6:13 PM on January 3, 2007

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