How much more does heat cost compared to air conditioning?

[GrandMasterK]

I am getting so unbelievably sick and tired of sweating in the spring/summer because my dad won't let me turn the AC on because it "cost to much". In the winter, he runs the heat constantly. Even now in the spring with 65-80 degree weather, he runs the heat every morning for 3 hours. In here (the computer room) it's always like 15 degrees hotter then it is outside and atleast 5 degrees warmer then the rest of the house.

[Phi for All]

Like most things, it's very subjective. Do you heat with natural gas, electricity, coal or oil? Is your AC part of a forced air system that cools the whole house the way the furnace heats the whole house, or is your AC in a window and designed to cool just one room? Are you in a moderate, cold or hot climate? How efficient is your AC system and will it be able to handle the load you want to put on it? How well insulated is your house?

 

Most central AC systems need electricity for the compressor, blower and fan and electricity costs are higher than natural gas, coal and oil. It does cost more to cool with electricity than to heat with natural gas, especially when you're asking your dad to cool the whole house for a problem with one room.

 

You should check out a portable evaporative, or "swamp" cooler for your computer room. I've seen them as low as US$87 online to cool 200 square feet. They add a little humidity to the air but in some climates that's a good thing. And since they move on wheels, you can take it wherever you need it so you're not having to cool the whole house.

[Norman Albers]

Homes often have reversible heat pumps for both heating and cooling. I know heating-wise efficiency goes from something like 2.8 down to 2.0 as outside goes below freezing. Those with generous wells sometimes do a water exchanger. I'd like to know the relative efficiency of the AC cycle when outdoors is 35C. .. .. .. .. .. .. .. .. .. ..A few years ago I got the smallest AC unit to mount in my back wall for those peak hot days. I'm glad I waited this long because they are much more efficient now, at 500W for an extraction of 5,000 BTU/hr. I used about $15 over two months of heat spells. .. .. .. .. .. .. .. .. .. .. A while back I compared heat available from raw electric hotplates vs. propane. It came out roughly equal.

[Norman Albers]

Be careful here. I am a 30-yr experienced piano tuner and rebuilder. Swamp coolers put plenty of humidity into the air, which is fine if you are west of the Rocky Mountains in the USA. In the east parts, summers are humid and the moisture is part of the air conditioning problem. Pianos are large and sensitive humidity gauges and I spend efforts with clients to stabilize their humidity level, so they can see I am a good tuner!

[GrandMasterK]

-I'm pretty sure it doesnt work when the power goes out, so electricity.

 

-We have two things. One is in the attic and one in the basement. If you turn heat/ac on on the first level, it will come out of the vents in the basement and the first floor. The one upstairs just comes out of the vents in the rooms upstairs. I dont think it comes on in the attic but I do know we have a fan in there that is supposed to turn on regularly to keep it cool in there.

 

-I live by Chicago, so inbetween. Fairly hot summers with humidity and pretty cold winters.

 

-I don't know how well insulted the house is. It's an upper middle class home so I'd imagine rather well?

 

 

-Every vent upstairs except my room is open. It's the pathetic attempt to get more air to come out in here.

 

 

-We have a humidifier downstairs that you have to fill with water. I'm...not even sure what the heck it's supposed to do. My parents got lazy and stopped using it awhile back, would that make it easier to get it cold in a room? I'm kinda frightened to run that thing in a small room, it makes the air seem sorta wet. Breathing in from your nose is a little more intense.

 

All I know is, if it passes 90 degrees outside, I can't get it cool in here for the life me no matter how long I run the damn thing. But temperatures like today, 75, there's no problem. Except he's always around to turn it off immediately.

[Phi for All]

I'm relatively sure you have natural gas forced-air heat and AC system (if your AC condensing unit is outside it's a split system, and if the attic unit pulls refrigerant from an outside unit it's a fan and coil system). The AC runs solely on elecricity so it costs more. The furnace uses gas to heat and electricity to run the blower and is therefore cheaper.

 

I like swamp coolers because they force air over a moist pad and the water does the cooling, but you don't need any more humidity with Lake Michigan helping out.

 

Your attic fan keeps the attic cool in the summer so that heat doesn't penetrate to the house through the roof. This helps a lot.

 

Do you have any fans going in your room? If not I would suggest an inexpensive oscillating fan ($12-$50) which doesn't cool as much but can be aimed so it doesn't blow papers off your desk. If you have a light fixture in your ceiling you could easily install a ceiling fan ($40-$150) that would really help in circulating air but it might cause a paperstorm when it's on high. Fans help in cooling and there's the psychological factor of feeling the breeze as well. Don't go cheap on fans - get a good one or you'll hear the hum of the motor.

 

The alternative is to talk your dad into a room AC unit that fits in your window ($180-$700). They'll draw electricity but not as much as your central system that's trying to cool the whole house.

[Norman Albers]

Part of your air conditioning need in summer is to get rid of humidity. When my house goes above 55%RH, I feel 'close' in that skin doesn't evapoate sweat as well as when it is 50% or so. The booklet for the AC says actually that it will 'take out excess moisture', which says that a compressor cold-side will quickly take water out of humidity-laden air. Observe that this necessitates the exchange of the heat of vaporization, and this is compressor work also! I say use a small AC upstairs and of course fans are smart. Windows curtained, as I talk about elsewherere, saves loss hot and cold. In summer you need to stop sun and conduction from hot air, both. If your upstairs system can be shut off in an unused room or two you can hog more of the air. Check the distribution conduits for tape-sealing and insulation, especially if they're in the hot attic. HEY PHI, given the multiplication from thermodynamics, what then is the relative measure? In the more rural West we have not the centralized natural gas you folks do so homes have propane trucked in. . . . . . . . Attics may have a power exhaust you can check, which speeds the super hot air going out the eaves or vent stack. Especially this is so when insulation lays on the ceiling of the upper room, and the roof-attac space is HOT.

[Phi for All]

HEY PHI, given the multiplication from thermodynamics, what then is the relative measure? In the more rural West we have not the centralized natural gas you folks do so homes have propane trucked in. . . . . . . .

As cheap as electricity is for most things, it's always one of the more expensive methods of heating a building. I don't have any figures and they would vary widely due to most energy not coming from regulated utility companies anymore (Chicago uses Dominion Energy, right?). I still think a propane heat system would be cheaper than an all electric system. Burning gas, oil or coal and using electricity to power the blowers is just cheaper.

 

You mentioned heatpumps earlier and they are great in the Southwest since you don't have to heat during freezing temps like you do in my area or in Chicago. Heatpumps can heat and cool and if it rarely snows in your area they are really efficient.

Attics may have a power exhaust you can check, which speeds the super hot air going out the eaves or vent stack. Especially this is so when insulation lays on the ceiling of the upper room, and the roof-attac space is HOT.

I'm a fan of radiant barriers as well. Two sheets of reflective aluminum sandwiching a mylar center to avoid conduction helps radiate heat heat back to it's source, keeping homes cool in summer and warm in winter. A radiant barrier usually lays on top of your attic insulation and can also be used on either side of the batting between studs in your walls, though it's less effective there.

[swansont]

Like most things, it's very subjective.

 

Did you really mean that? It's thermodynamics/mechanical engineering, so it's not very subjective at all.

 

Anyway, all else being equal, heating will be cheaper than cooling because of basic thermodynamics. When you cool, you have to reject some heat, and your efficiency is limited.

[Norman Albers]

Infrared radiant loss is usually roughly one-third of the total load, so yes radiant layers that reflect back across some space, like the vented attic with the super-hot roof. How's this idea of mine and Tom Sawyer??? Remember he whitewashed the fence? Is there a simple whitewash we could spray on our roofs in summer? I have medium-light colored 3-tab shingles but white would be cooler. . . . . . . . . . . . Hey Swansont, in either heating or cooling with a heat pump, you are pushing heat against a similar gradient. I recall, though, that thermodynamic efficiency is a ratio of a difference to an absolute temp, or some such. Typically I cool against a 15C difference, and heat against maybe 18C. We in the Pacific NW have enjoyed relatively low electric rates; I'm not telling.

[Phi for All]

Did you really mean that? It's thermodynamics/mechanical engineering, so it's not very subjective at all.

Of course I meant that. The OP didn't tell me anything about his system or his environmental requirements, other than he was too hot in his computer room in the spring/summer and he has AC capability.

 

I could make a case for electric baseboard heat and a tankless water heater if the user were single, lived in a 500 s.f. home in Atlanta, showered every other day, worked 12 hour days and slept at his girlfriend's house three nights a week. The same system wouldn't be as efficient for a couple with an infant in Fargo ND who work from home.

[Externet]

Heating a home in general is considered more expensive than cooling, if both energy sources are at the same rate.

 

Cooling process is lossy because of the compressor, evaporator and condenser inefficiencies, but the temperature gradient overcomes those losses.

 

Cooling happens when the temperature is about 32 Celsius, and you want to extract heat for a delta temperature of about 10 degrees to get a comfortable 22 Celsius.

 

Heating happens when temperature is around 0 Celsius and you want to add heat to reach about comfortable 20 Celsius.

 

The delta temperature is twice for typical heating, the cost is nearly twice for heating.

 

If you want to heat / cool the same amount of degrees, cooling is more expensive.

 

Miguel

[Norman Albers]

Relatively can we say the low 'sink' in the cycles is maybe 20C or so different, and that this approaches 10% of the absolute temp 0f 273K? Is the cooling worse than 10% more difficult?

[swansont]

Of course I meant that. The OP didn't tell me anything about his system or his environmental requirements' date=' other than he was too hot in his computer room in the spring/summer and he has AC capability.

 

I could make a case for electric baseboard heat and a tankless water heater if the user were single, lived in a 500 s.f. home in Atlanta, showered every other day, worked 12 hour days and slept at his girlfriend's house three nights a week. The same system wouldn't be as efficient for a couple with an infant in Fargo ND who work from home.[/quote']

 

Yes, but those are all objective bits of data. Subjective means that you and I can come up with different answers depending on our differing opinions and feelings.

[Phi for All]

Yes, but those are all objective bits of data. Subjective means that you and I can come up with different answers depending on our differing opinions and feelings.

I stand corrected. I was wrong.

 

I was confusing variation with interpretation.

[Prime-Evil]

I think you have to consider exergy analysis. Heating hot water should cost more than heating a room. If you use electric heat both cost the same, but heating a room with electric heat is arguably more wasteful because there are easier alterneative. For example, a heat pump can achieve a higher capacity factor heating a room to 70degF than water to 140degF.

 

In general, air conditioning is more wasteful than heating because the energy you use adds to the problem, whereas with heating the energy you use running a motor and so forth at least helps accomplish your goal.

[Norman Albers]

You must distinguish between the useful thermodynamic work done by the motor/compressor, which might be 3/4 of the power input (?). What is wasted as heat of the motor can be recovered only in the case of heating. This is a slight advantage but not to be confused with basic thermodynamics. If these numbers hold for analyzing my little 500-W A-C unit, a loss of 125-W is (factor of 3) 375 BTU/hr. The unit is rated at 5,000 BTU/hr, so here is a 7-8% difference, yah???

[Prime-Evil]

That's more or less what I was thinking. A 500w Heat Pump unit might produce 1500w of heating. Run in reverse at the same COP it would produce only 1000w of cooling, so I get a difference of 33%. Of course it also depends on whether it is located inside your house or out. Its hard to compare real data because everyone likes to work in funny units like TONS and stuff and its difficult to compare apples with apples when a system is designed and located primarily for one and not the other.

 

The delta-T of course makes a difference also, but we are assuming that is the same. Depends on where you live of course. It is easier to heat in Florida obviously, and easier to cool in Nunavut.

[Norman Albers]

Aha, am I missing this? I shall review the heat cycles, with mechanical and heat energies. Location matters only for the loss component. Swansont was driving at the same point. . . . . . . . . .Time passes. . . . . Yes I see finally. Say with my AC unit, 500W, which is equivalent in heat to 1500 BTU/hr, is the input which drives 4500+BTU/hr. out. So disregarding loss, all 6,000 BTU of the sum are being thrown out. I we were using that, using the heat to heat ourselves, we would be getting 6,000 rather than 4,500 BTU/hr move for the same 500W input.

[Prime-Evil]

Yeah. That's a much simpler way to explain it than my way.

[Prime-Evil]

Now what GrandMasterK needs to do is save up and buy his old man a heat pump, and have the AC side in his room and the heating side in the Old Man's room.

[Norman Albers]

Not simpler, just clearing out parameters. Yo, babe, I did entertain the idea of putting my little Sanyo refrig. into the window, for 160W x 3 = 500BTU/hr. WHOA, BETTY.

[Prime-Evil]

LOL.

It would be nice to see more small efficient heat pumps. I have thought of making one that would use inside stale and humid air as the heat source and using the heat to heat my hot water. It would depressurize my house slightly, but I would have cold air leaking in instead of warm air leaking out without any heat recovery. I have a semi-leaky house.

 

The other think to do would be to keep making ice and tossing it outside, but by spring you would have a huge mountain of ice in your backyard. I suppose you could they bring it inside and use it for refrigeration and iar conditioning, but I think flooding would be a major concern.

 

160w Sanyo

500 BTU/h x 24h/day x 180 days / 150 BTU/lb

= 7.2 Tons = 8 cubic meters of ice !

WHOA Betty is right.

[Norman Albers]

You have a semi-leaky and highly intelligent brain.

[Prime-Evil]

Hehe. Your sort of half right anyways.

Highly-leaky and semi-something.