Here is some math
Hi Mark,
Why Winter time is NA (Not Applicable?)
There is nothing to do with season, it does not matter.
Ok, here is some math.
BTU is amount of heat energy required to raise one pound
of water one degree Fahrenheit.
Gallon of water is 8.33 pounds;
10min shower required about 20 gallons of water
(assuming shower head rate is 2Gallons per Minute)
or 20x8.33= 166.6pounds.
Assuming inlet water temperature is about 40F and
temperature, comfortable for taking shower is about 100F.
So, one 10minutes comfortable shower required
166.6(100-40)=166.3x60=9996BTU (~10,000BTU)
regardless of energy source (Gas/Oil/Electric/Solar/etc.)
and regardless of season (Winter, Spring, Summer, Fall).
Assuming heat conversion efficiency is 80%, energy source
must supply 10000/0.8=12,500BTU
One gallon of heating oil could produce about 140,000BTU
The above shower will need about 12,500/140,00=0.089
gallons of heating oil. And finally if price per gallon is $3.00
then cost of one 10 minutes shower is 3x0.089=$0.269
So, just a shower for 4 people per day is a bit more then $1.00
or about $400 a year.
Electricity versus oil:
1BTU=1055Joule;
1KWH=3,600,000Joule;
Or 1KWH= 3600000/1055=3412BTU
or Energy from burning of 1 Gallon of Heating Oil is equal
to 140,000/3412=41Kilowatt*Hour of Electric Energy.
If price for 1KWH is about $0.15 then the same energy
from electricity is about twice expensive then from burning
oil 41x0.15=$6.15
Well, I am not surprised: Most of the Electricity is coming from
burning oil/coal plus overhead.
- Vitaliy