This is the sector that can benefit most from solar energy, both passive and active

Major issue to face to one of timing. Buildings have lifetimes of 50 to 100+ years, so decisions made (or not made) today have impacts for a long time.

This is also one of the sectors over which we as individuals have primary control… so our actions as individuals have direct and lasting impacts.

Energy use in the home

Types of use and amount of energy used, in percent

Space heating	53%
Water heating	18%
Appliances	16%
Air conditioning	5%
Refrigerators	5%
Lighting	3%

About 1/3 of this energy is consumed as electricity, the rest directly as fossil fuels (mostly natural gas and fuel oil.

Energy efficiency in the home

Major energy use is in heating and cooling.

Major gains can be made both in the efficiency of those systems and in preventing the need for these uses of energy, such as:

• better insulation
• more use of passive solar
• more use of active solar, photovoltaics and water heating

Heat losses in a typical home:

Major losses via improperly constructed or maintained walls, windows and doors: 38%

Significant losses also via poor insulation in windows and walls: 33%

Basement walls are the other main loss point: 20%

Energy Savings

Energy consumption in the average home in the United States could be cut in half… if not further.

Where and how to save energy.

Type % savings How

Space heating	300	Improve Insulation
Water heating	50	Insulate tank, low flow shower, cold water laundry
Space cooling	100	Improve Insulation
Lighting	30	Fluorescent lights

Payback period

The costs of fixing energy leaks can be recovered from the annual savings in home energy costs (heating and air conditioning, for example)

The time it takes to break even after the initial investment is called the payback period

Payback period = Initial investment ($)

Savings ($ per year)

The payback period needs to be short enough for people to be willing to make the initial investment. Issues are:

• Average time a home is owned (about 5 years)
• Size of initial cost
• Long term view vs. short term view

Typical Payback periods:

Insulating new walls, and roofs: <1 year

Insulating existing walls, and roofs: 4 to 6 years

Insulating existing basement walls: 10 to 20 years

Replacing windows: 3 to 5 years

These are for older homes (20 + years old).

Problem arises in the mismatch between the payback period and the average time we own homes before moving, etc.

If the payback period is longer than about 5 years, we don’t make the investment.

Electricity use in the home

Appliance	kWh/yr.	Cost/yr. ($)	% of total*
Air conditioner (room)	1070	85.6
Air conditioner (central)	3230	258.4	18.8
coffee maker	100	8	0.6
clothes dryer	1060	84.8	6.2
clothes washer	1080	86.4	6.3
dishwasher	935	74.8	5.5
electric blanket	120	9.6	0.7
furnace fan	600	48	3.5
home computer	130	10.4	0.8
lighting	844	67.52	4.9
microwave oven	220	17.6	1.3
kitchen range	840	67.2	4.9
refrigerator	1300	104	7.6
stereo	75	6	0.4
television	197	15.76	1.1
television off	33	2.64	0.2
toaster oven	50	4	0.3
vacuum cleaner	25	2	0.1
VCR	40	3.2	0.2
waterbed	960	76.8	5.6
water heater	5300	424	30.9
Total (central AC)*		1371.12

The major users are water heating and air conditioning (discussed earlier).

Next comes washer and dryer and dishwasher.

• Upgrade to more efficient appliances when possible. (European washers use about half the electricity, for example.)
• Use appliances less frequently, if possible.

   

• Lighting

In combined residential and commercial sectors, lighting accounts for about 20% of all electrical energy, or about 5% of all energy used in the United States.

Florescent lights are 4 to 5 times more efficient than typical incandescent lights (in terms of light produced per unit energy used).

Fluorescent lights also have much longer lifetimes, typically 10 times longer than incandescent bulbs. The payback period with fluorescent lights is usually a few months.

Solar use in Residential/Commercial sector

Nearly all of home and office energy needs could be met with passive and active solar energy.

Some dependence on other forms of energy is needed to deal with the reliability issue… the sun does not always shine!

Hundreds of companies now sell solar energy products.

Easy applications:

• Passive solar heating
  Via house orientation and window layout

  Via solar collectors… cost is typically a few thousand $ per home.

   

• Hot water heating. Typical systems cost about $1000 for family of 4 sized system

Solar augmented homes need not sacrifice aesthetics…

Remote home in the Florida Keys: energy independent

Home in New Jersey… also energy independent

Street view:

South view:

Note both water heating and photovoltaics

Wind energy systems are also commercially available… advertisement from company

Total cost for a system is typically $500 to $1000 per home

• Energy savings of 50% or more are easily attained, mostly in more efficient heating and cooling.
• Use of passive solar energy is an obvious energy saving step. Could cut residential/commercial energy use to 10 to 20% of today’s use (factor of 4 or 5 cut in energy use).
• Know where energy is used at home and work… focus energy savings on those major energy users.