Author Topic: Energy usage and programmable thermostats  (Read 673 times)

Offline bluefoxicy

  • Brewer
  • ****
  • Posts: 304
    • View Profile
Energy usage and programmable thermostats
« on: January 05, 2011, 02:22:46 PM »
In November, my energy bill was $68

In December, $115

My electricity bill was $52 in November and $98 in December.

I keep my heat off, and have a small fan-forced heater in my bedroom.

What I've learned:  When it's friggin' cold, that heater runs a lot. It also costs about $45 more for a 15 degree difference.

Some considerations I've made for this year, then:

  • Put the heater and the window AC unit on a power strip.  Switch the power strip off when I leave during the day; switch the power strip for the heater off at night when cold.  Blankets work great in the winter (I've tried), and both units are digital and thus draw annoying (small) amounts of power to run small computers.  I can live for 5 minutes when I get home without heat or AC; can't sleep in a hot room, so I'll run the AC at night.
  • Consider shutting down the computer at night.  This is annoying, but "Standby" mode uses less than 5 watts.  That and the fan-force heater both contribute a lot of noise at night; the quiet is better.

Seriously, my power bill could hit about $30 or less if I knocked out the 250 watt computer and the 800 watt heater and the 1000 watt AC for about 10-20 hours a day.  As it stands, there's about 1050-1250 watts in use that don't need to be in use.

Since the heater and computer will run for about 5 hours in the winter, that's 1050 * 19 * 30 == 585000 == 585kWh potentially saved, although the heater runs about 30% of the time and thus it's more like 490 * 19 * 30 == 279kWh, which actually makes sense.  For reference, with the computer and heater running 24 hours a day, November's power usage was 348kWh and December's was 691kWh; the only change was the outside temperature, so the extra run time for the heater accounted for 343kWh (of a possible 576kWh for continuous running of the device, meaning it was using under 233kWh in November and thus running under 40% of the time).  Thus, I can reduce my power usage by roughly 80% in the winter (other stuff used 115kWh).

Let's take some stats for this.

Minus computer, AC, and heating, my base power usage is 115kWh.

24 hour heating and computer uptime accounts for roughly 233kWh.  Heating in the cold month alone pushed up 343kWh; 100% heater utilization is 576kWh.

24 hour peak power computer uptime (250 watt PSU) would account for 180kWh; my computer probably actually draws 30 watts normally, around 21kWh.

The summer is more difficult.  The air conditioner (9 amp * 110 V = 990W ~= 1kW) must run for 14 hours a day (5pm-7am) but the computer only 4 hours a day (5pm-10pm).  Thus my summer savings would come to ((1000 * 7) + (250 * 19)) * 30 == 352kWh.  In July I used 626kWh of electricity; not even yet as much as the heater, but close.  Then again, I'm trying to bring down from 90-95 to around 78, about 12-17 degrees; not up from 30 to 78, around 48 degrees, so the AC has less work to do.  The AC is bad at it.

The best I can do here is guess.  If I guess 21kWh for the PC and 115kWh base, that's 136kWh and the AC did 490kWh!  If so, cutting that back by about a third would land me at 323kWh, plus the 136, giving 459kWh total in July.

So lessons learned:

  • Heating is expensive.
  • Air conditioning is more expensive.
  • Leaving your computer on is not expensive.

Now think about those programmable thermostats.  A few degrees warmer around midnight, when you're likely asleep... a few degrees cooler around 5am, because you'll wake up around 6... not much of a difference really, but shifting from 75 to 85 and then back will do wonders.  The same in winter, shutting the heat completely off at night and between 10am and 5pm.  Consider when you have a whole house to heat, too....

Here's to the coming summer!


Offline Kaiser

  • Global Moderator
  • Senior Brewmaster
  • *****
  • Posts: 1797
  • Imperial Brewing Geek
    • View Profile
    • braukaiser.com
Re: Energy usage and programmable thermostats
« Reply #1 on: January 05, 2011, 02:39:59 PM »
Heat loss is proportional to the difference between the inside and outside temp. If the outside is at 10F and you drop the inside temp from 75 to 65 you drop the temp difference from 60 to 50 which means  you have (60-50) /60 = 16% less heat loss which you don’t have to make up for by heating.  If the outside temp is at 30F you save even more (25%).

I have thought about this a lot. With oil prices being as high as they are it just makes sense.

Another thing that helps, is to close unused rooms and turn-off the heat or close the air registers.

Kai

Offline MDixon

  • Senior Brewmaster
  • ******
  • Posts: 1244
    • View Profile
    • Mike's Homebrewing Page
Re: Energy usage and programmable thermostats
« Reply #2 on: January 05, 2011, 05:42:07 PM »
I once lived in a house heated by two gas fired heaters and two window unit AC units. Heat was astronomical in the uninsulated home. I seem to recall 1500-2000 per heating season. Cooling was much less. My take away was insulation is KING!
It's not a popularity contest, it's beer!

Offline beerocd

  • Senior Brewmaster
  • ******
  • Posts: 1429
    • View Profile
Re: Energy usage and programmable thermostats
« Reply #3 on: January 05, 2011, 07:08:45 PM »
Another thing that helps, is to close unused rooms and turn-off the heat or close the air register

Apparently HVAC guys hate when you do this. All vents, all doors should be open. At least that's what I've been told. That's for optimal operation, not necessarily most economical operation. There's got to be an HVAC guy on the board who can explain this better.
The moral majority, is neither.

Offline bluesman

  • Global Moderator
  • I must live here
  • *****
  • Posts: 8808
  • Delaware
    • View Profile
Re: Energy usage and programmable thermostats
« Reply #4 on: January 05, 2011, 07:45:52 PM »
The key to reducing your heat bill lies in your heater, home insulation and your usage.

A high efficiency gas furnace heating a house insulated to an appropriate R-value will yield a lower heating bill than a house with minimal insulation heated by an oil burner. Alot of heat loss can occur at windows and doors. Walls should be insulated to at least a standard R11 value. Your geographic location plays a very important role as well.  ;)

Here's a website that specs out insulation.

http://www.ornl.gov/sci/roofs+walls/insulation/ins_16.html

http://www.reliableplant.com/Read/15871/maximize-system-energy-efficiency-with-proper-insulation
Ron Price

Offline Kaiser

  • Global Moderator
  • Senior Brewmaster
  • *****
  • Posts: 1797
  • Imperial Brewing Geek
    • View Profile
    • braukaiser.com
Re: Energy usage and programmable thermostats
« Reply #5 on: January 05, 2011, 07:49:26 PM »
Another thing that helps, is to close unused rooms and turn-off the heat or close the air register

Apparently HVAC guys hate when you do this. All vents, all doors should be open. At least that's what I've been told. That's for optimal operation, not necessarily most economical operation. There's got to be an HVAC guy on the board who can explain this better.

I think this may have to do with the return vents. They may may not want to be behind closed doors.

Kai

Offline weazletoe

  • Brewmaster General
  • *******
  • Posts: 2166
  • Mecca, Ohio
    • View Profile
Re: Energy usage and programmable thermostats
« Reply #6 on: January 05, 2011, 09:13:41 PM »
Another thing that helps, is to close unused rooms and turn-off the heat or close the air register

Apparently HVAC guys hate when you do this. All vents, all doors should be open. At least that's what I've been told. That's for optimal operation, not necessarily most economical operation. There's got to be an HVAC guy on the board who can explain this better.

OOHHHHH!! OOHHHHHHH!! I'm an HVAC guy.  The problem with this is such....You'r furnace and a/c is desigend to heat /cool all the rooms of your house. The furnace is sized to the sq. footage of the home, and the duct is sized all the way from the furnace, to the very last register at the end of the line. You'll notice that the duct gets smaller the farther down the trunk it goes. This is to keep the preassure up, as air is lost through the registers. Each room needs to have air dumped into it. The air the furnace is forcing has to go somewhere. If you close off rooms, the air has no where to go, and creates back preassure. Not only does this screw up the air opreassure in the other rooms of the house, but if to much back preassure builds up, it can prematurely wear out the heat exchanger. Or, in a/c season, cause your coil to freeze. PLEASE!!!!Leave your dampers alone guys!!! when a system is installed, the dfampers are carefully set. I know it seems like no big deal, but this is one case when you;re besat off to leave well enough alone.
A man works hard all week, so he doesn't have to wear pants all weekend.

Offline beerocd

  • Senior Brewmaster
  • ******
  • Posts: 1429
    • View Profile
Re: Energy usage and programmable thermostats
« Reply #7 on: January 05, 2011, 09:18:08 PM »
Another thing that helps, is to close unused rooms and turn-off the heat or close the air register

Apparently HVAC guys hate when you do this. All vents, all doors should be open. At least that's what I've been told. That's for optimal operation, not necessarily most economical operation. There's got to be an HVAC guy on the board who can explain this better.

OOHHHHH!! OOHHHHHHH!! I'm an HVAC guy.   PLEASE!!!!Leave your dampers alone guys!!!

See.
The moral majority, is neither.

Offline Kaiser

  • Global Moderator
  • Senior Brewmaster
  • *****
  • Posts: 1797
  • Imperial Brewing Geek
    • View Profile
    • braukaiser.com
Re: Energy usage and programmable thermostats
« Reply #8 on: January 05, 2011, 09:53:54 PM »
Good point. As much as I like forced air systems b/c they can heat and cool, this is an aspect that I don't like as much. 

Kai

Offline euge

  • I must live here
  • **********
  • Posts: 7646
  • Estilo Casero
    • View Profile
Re: Energy usage and programmable thermostats
« Reply #9 on: January 05, 2011, 10:40:36 PM »
I have a totally programmable 7 day thermostat. Got it at Lowes for less than $100 and it has made a hell of a difference. AC comes on when it needs to and heat comes on automatically- sometimes both in the same day. I don't have to do a thing except program it.

Besides leaving all the room doors and vents open (hvac advice) I cleaned the intake under the inside unit and sealed all the crevices in there with spray foam. Now it is about 200% more quiet and works more efficiently.

Funny thing is when the weather is hot during the day and cool at night I'll place one of those dual exhaust fans in the kitchen window and open another at the opposite end of the house. It cools the house right on down and the AC doesn't have to kick on.

In the winter my 50" TV heats the living room.  ;D
The first principle is that you must not fool yourself, and you are the easiest person to fool. -Richard P. Feynman