Electric Mattress Pad

We have been trying to turn down the heat in the "bedroom wing" of the house to save energy, but find that we (actually me) can't go below about 62F without being cold most of the night, even with a down comforter.  We decided to try these electric mattress pads after staying in some places that had them in New Zealand.  We are now able to sleep toasty warm with the bedroom at 49F.   I think that the energy saving is considerable -- see the calculations below.

 

These electric mattress pads go over or replace your regular mattress pad and live under you rather than over you like an electric blanket.  I think that they use a lot less power than an electric blanket.  The cost is in the $50 to $150 range depending on the size of bed and brand.

 

Mode of Operation:

Ideally we turn the pad on high 15 minutes before bedtime to pre-warm the bed.  After the warm up, I leave mine on about setting 2, and my wife either uses setting 1 or turns it off.

 

Energy Saving:


Energy Used:

I measured the power consumption with a Kill-A-Watt meter, and got the following:

 

setting       Power

1                9   watts

2                17

3                25

4                33

5                43

 

A full night of power consumption for my half was 0.16 KWH -- I am guessing that it would be about 0.25 for the two of us.  So, the cost per night is (0.25 KWH)($0.1/KWH) = 2.5 cents.

Energy used 0.25 KWH per night.

 

Energy Used:

I believe that the pad allows us to run the bedroom areas about 10F to 12F cooler than we would otherwise.  For us this is a 24 hour a day setback.

 

The saving for our bedroom geometry is about:

 

Windows:   (61sqft)(11F setback)(24 hr/day)/R2               = 8000 BTU/day

Walls:         (500 sqft)(11F setback)(24 hr/day)/R20          = 6600 BTU/day

Ceiling:       (430sqft)(11F setback)(24hr/day)/R40           = 2800 BTU/day

Floor:          (430sqft)(11F setback)(24hr/day)/R40           = 2800 BTU/day      (R40 is a guess at the effective R)

                                                                                                    -------------------

Total                                                                                           20,200 BTU/day

 

With our 90% efficient furnace, this is (20200 BTU/day)/(0.9) = 22400 BTU/day or 6.6 KWH/day

 

Net energy saving is = 6.6 KWH saved - 0.25 KWH used = 6.35 KWH net energy saved per day, or 2318 KWH/year

 

 

Cost Saving:

Cost of electricity:

Electricity used is 0.25 KWH per night, or 91 KWH/year.

At 10 cents per KWH, this is worth $9.10.

 

Savings in Propane

Gallons of propane saved per day = (22400 BTU/day)/(92000 BTU/gal) = 0.243 gallons per day, or 89 gallons/year

At $2.20 per/gal, this is worth $195 per year.

 

Net Saving:

Net yearly saving for the electric mattress pad = $195 - $9.10 = $186

 

So, the payback is less than one year!!

 

CO2 Saving:

CO2 emissions due to electric pad = (0.25 KWH/day)(2 lb CO2/KWH) (365 days) = 183 lb emitted due to elec pad

 

CO2 emissions saved due to setback = (7.3 KWH/day)(0.5 lb CO2 /KWH) (365 days) = 1332 lbs CO2 saved

 

Net CO2 saving = 1332 lb - 183 lbs = 1150 lbs net saving in CO2 emissions

 

 

A 12 Volt Model

Here is a model that works on 12 volts for off-grid or RV use.

http://cornstoves.com.bizhosting.com/electrowarmth_bedwarmer_photo_page.html

 

 

Other Warm Bed Suggestions:

 

Down Comforters:

Some people find that they can live easily with lower bedroom temperatures by using a heavy down comforter.

 

Taking Care of the Initial "Cold Bed" Chill:

"We use a cloth sack filled with feed corn given to us by a friend many
years ago (thank you Pete the pirate). We heat it in the micro-wave oven
as if it were pop corn (no it doesn't pop), then use it as a foot
warmer in bed (or anywhere cold feet or pulled muscles are a problem).
Works great."

Questions, Answers and comments on above scheme:

How many uses do you get out of it?
Do you have to add moisture to it from time to time to replace what
the microwave drives out?
Roughly how large a sack?

"We've had ours in use every winter for 5 years now. No signs of wear.
Pete was in the custom canvas business at the time, and made it out
of a scrap piece of "Sunbrella" acrylic yacht canvas (9x11" finished
size- probably because of the size of scrap he had on hand. The corn
always seems to give off a slighty moist heat, and faint corn aroma.
I suspect it reabsorbs moisture from the air. When I get my machine
out of storage , I'm going to try making some out of organic
materials. (My daughter and wife usually want the "Corn Pack" at the
same time)."

 

Another Scheme:

"I've heard that buckwheat seed works well too, but my good buddy Paulette the wonder seamstress, used to sew a couple of (new & usually cute) kitchen hand towels together, into a "pillowcase" shape, and fill it with maybe 4 pounds of regular (not minute) rice, then sew the open end closed.  This size you should be able to microwave 3-4 minutes safely.  If you're putting it directly on a person, you'll want to wait a few minutes after microwaving to avoid TOO much heat, but as a bed warmer, no wait required!  Paulette said for the deluxe, slightly aromatic version, you can use Jasmine rice instead, and if you want to wash the cover, or change the rice inside if it "wears out" -  (?),  just take out the last seam and remove rice... refill and sew again later.   I've been using a commercially available one of these, called a "bed buddy" for years with no signs of anything wearing out, but not sure what it has in it ... could be rice ... it does produce a slightly moist heat like the rice does.   Mmmmm - comfy on those chilly nights!

For the quick and easy "no sew" experimental model - a clean, all cotton tube sock, with 1 to 2 pounds of rice works too.  If the sock it too thick to knot the open end securely, after microwaving, you can fold over in a non-leaky way and safety pin shut.  (This size, try microwaving 1 1/2 to 2 minutes)

Been wanting to experiment with Jasmine rice or maybe adding something aromatic (could be a few cedar branch tips???)  - I'll let you know how it works if I do.

PS - beware of rodents! - If you're storing one of these for awhile they can be tempting for the little visitors if you're not careful!   "

 

 

Here is a product offered by Brookstone that offers both heating and cooling in a mattress topper:

 

Brookstone "Chili Pad" ...

 

From Brookstone description:

Cool mattress pads promote better sleep!
ChiliPad dual control heated mattress pad quietly heats or cools your bed for a comfortable, restful sleep. Bed too cold? Too hot? ChiliPad makes it feel just right! Now you can safely raise and lower bed temperature to suit your perfect sleeping environment. Order your ChiliPad heated mattress pads today and improve your nights by degrees!

Heated mattress pads are better than electric blankets.
The ChiliPad mattress topper uses water to regulate temperature. As a result, this dual control heated mattress pad doesn’t create the electromagnetic field wired blankets can. And unlike blankets, ChiliPads can also work as cool mattress pads on hot summer days.

Not cheap at $400 to $900, but I could see making one?

 

 

 

 

 

 

 

 

 

Gary

12/9/05, Feb 10, 2008