[Greenbuilding] cost of electric versus natural gas and gasoline

[Reuben Deumling]

On Sun, Mar 9, 2008 at 5:10 AM, Ted Inoue <tedinoue at gmail.com> wrote:

> Ben,
> For a comparison like this, one must also consider the efficiencies of the
> energy conversions involved as that makes a substantial difference in the
> outcome of the comparisons.
>
This is a very important point, and doing so will reveal that the 100%
efficient electric energy (measured at the level of your house) must--as
others have pointed out on this list in the past--be multiplied by the
efficiency with which coal or natural gas or oil was burned at the power
plant where the electricity that is delivered to your house was produced.
Commonly this is assumed to be somewhere around 35% or .35.  Transmission
and distribution losses are commonly also tallied in the case of
electricity.

>
> For example, if you use electric baseboard heaters to heat a house, that
> delivers "electric heat" at essentially 100% efficiency. Every kilowatt
> hour
> of electricity pumped into the baseboards delivers the full 3413 BTUs of
> heat.
> On the other hand, a natural gas furnace will have a combustion efficiency
> that diminishes the actual BTUs delivered to heat the home. If you buy one
> therm and that is combusted at 85% efficiency then you've lost 15% of the
> energy right off the bat, and have to figure that in.

Including the losses at the source then would suggest a rather different
comparison between electricity and natural gas as a heating fuel:
electricity: 35% (not counting T&D losses) vs. natural gas or propane:
65-85%


> Next, you typically wouldn't run straight electric resistance heat, but
> instead would use a heat pump. A good heat pump delivers 8-9 BTUs of heat
> for every one watt put in (see the HSPF rating). This effectively improves
> the comparison in favor of electric heat by a factor of 2+.
>