justoffal
Diamond Member
- Jun 29, 2013
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Did some KWH testing to see if turning down the thermostat and covering up with an EB might be helpful this winter for your heating bills.
Remember that the relationship between your temp setting in your house and the total cost of heating the house are definitely related based
on the basic laws of thermodynamics wherein Q is a product of Delta T.... ( Total heat transfer is a result of total temperature difference ) even a well insulated home ( not sure about the new passive homes ) will leak heat to a sink ( being the cold exterior ) based on the TTD....the better the insulation the slower the process but the process remains nevertheless.
View attachment 565248 h equal to the HT coefficient ( assignable according to the material being used to insulate ) A equal to total area in square meters and Delta T being measured in Kelvin scale.
View attachment 565260 Let's assign a material.....wood for instance to the diagram. The average Thermal conductivity is about .15 (SI units) so if you want to run 68 F in your house ( 293k) on a day where the ambient temperature outside was 28 F ( 270k) and wood was your insulator this is what you would be looking at....
Total Heat Transfer in watts ( moment by moment) is .15 (1 square meter* 23) or 3.45 watts per moment ( a second will do) per square meter. The Greater the number in the parentheses the greater the transfer and the larger your energy usage. 28 works out to 4.2 watts ( if you opted for 78 degrees in your house ) ..... you can see where this is going....if you opted for 58 F for night time you would reduce to 2.55 watts or 27% less energy wasted to external transfer. On the new typical energy bill 27% can add up very quickly. The problem of course is that most people are not comfortable at 58F But! What about covering up a little more?
I decided to try it. using several different models of Electric blankets ( which also use energy) to see if they made the difference in comfort. Using my average heating bill per day ( I have a big place...poorly insulated .....my preference.....and a big heating bill to go with it if I decide to run a 68 F for the duration. But what do I save with 58F and will I be comfortable and is it worth the electricity? The answer is a lot...yes and yes again.... If I use the full measure of a 28 day month of hours typical heat use equal to approx $600.00 ( based on the new energy rates ) lets say I run at 58F from 9pm to 9am and therefore cut out 27% of the usage waste for that period. Daily cost about 22 bucks or 11 bucks per 12 hours looks like ...11-8.03 or $2.97 per day....$83.00 per month. Cost of electric blanket on highest setting for 12 hours is about .05kwh/hour *12 or .6 KWH which is most parts of the country is about 30 cents these days ( ridiculous! ) so your total cost savings is at $2.67/day$74.75/month....but I'm not done.
Next I tried using a blanket over the EB to keep all the heat going toward the bed and I put a space blanket ( High R factor ) under the sheets which took the total usage of the EB from .05kwh/hour to .03kwh per hour or a 40 percent increase in savings. This brings us to $107.50 in savings per month on the bill...which is still a monster but that's my own fault.
A good EB is about 80 bucks....so it pays for itself ( for me ) in less than a month....and....it was quite comfortable. Is it worth it??....it probably is.
JO
Remember that the relationship between your temp setting in your house and the total cost of heating the house are definitely related based
on the basic laws of thermodynamics wherein Q is a product of Delta T.... ( Total heat transfer is a result of total temperature difference ) even a well insulated home ( not sure about the new passive homes ) will leak heat to a sink ( being the cold exterior ) based on the TTD....the better the insulation the slower the process but the process remains nevertheless.
View attachment 565248 h equal to the HT coefficient ( assignable according to the material being used to insulate ) A equal to total area in square meters and Delta T being measured in Kelvin scale.
View attachment 565260 Let's assign a material.....wood for instance to the diagram. The average Thermal conductivity is about .15 (SI units) so if you want to run 68 F in your house ( 293k) on a day where the ambient temperature outside was 28 F ( 270k) and wood was your insulator this is what you would be looking at....
Total Heat Transfer in watts ( moment by moment) is .15 (1 square meter* 23) or 3.45 watts per moment ( a second will do) per square meter. The Greater the number in the parentheses the greater the transfer and the larger your energy usage. 28 works out to 4.2 watts ( if you opted for 78 degrees in your house ) ..... you can see where this is going....if you opted for 58 F for night time you would reduce to 2.55 watts or 27% less energy wasted to external transfer. On the new typical energy bill 27% can add up very quickly. The problem of course is that most people are not comfortable at 58F But! What about covering up a little more?
I decided to try it. using several different models of Electric blankets ( which also use energy) to see if they made the difference in comfort. Using my average heating bill per day ( I have a big place...poorly insulated .....my preference.....and a big heating bill to go with it if I decide to run a 68 F for the duration. But what do I save with 58F and will I be comfortable and is it worth the electricity? The answer is a lot...yes and yes again.... If I use the full measure of a 28 day month of hours typical heat use equal to approx $600.00 ( based on the new energy rates ) lets say I run at 58F from 9pm to 9am and therefore cut out 27% of the usage waste for that period. Daily cost about 22 bucks or 11 bucks per 12 hours looks like ...11-8.03 or $2.97 per day....$83.00 per month. Cost of electric blanket on highest setting for 12 hours is about .05kwh/hour *12 or .6 KWH which is most parts of the country is about 30 cents these days ( ridiculous! ) so your total cost savings is at $2.67/day$74.75/month....but I'm not done.
Next I tried using a blanket over the EB to keep all the heat going toward the bed and I put a space blanket ( High R factor ) under the sheets which took the total usage of the EB from .05kwh/hour to .03kwh per hour or a 40 percent increase in savings. This brings us to $107.50 in savings per month on the bill...which is still a monster but that's my own fault.
A good EB is about 80 bucks....so it pays for itself ( for me ) in less than a month....and....it was quite comfortable. Is it worth it??....it probably is.
JO