Resources
Definitions:
BTU: energy needed to raise 1 pound of water by 1 degree F (144 BTU to melt 1 pound of ice)
CFM: Cubic Feet per Minute, air flow for heating or cooling
EER: Energy Efficiency Ratio for air conditioner: BTU/hour per input watt
Footcandle (FC): the illumination from a standard candle at a distance of one foot
HVAC: Heating, Ventilating, and Air Conditioning
Lumen (luminous flux): the light from a standard candle at a distance of one foot over 1 square foot area
Lux (illumination): one lumen per square meter
MERV: Minimum Efficiency Reporting Value for filters (related to percentage of particulates captured)
SEER: Seasonal EER: BTU/Watt hour, averaged over cooling season (different conditions than EER)
Therm: unit of energy, equal to 100,000 BTU (heat produced by burning about 100 cubic feet of natural gas)
1 ton AC: 12,000 BTU/hour
Rules of Thumb (for Southern California unless otherwise noted) (can be used to catch simulation errors):
Buck A Watt: a 1 watt device costs $1 to power continuously for a year, given a utility rate of 11.4 cents per kilowatt hour (very cheap, most of California is 15 cents)
Typical AC uses 400 CFM/ton air flow
Fresh outside air: use 5 to 20 CFM per person; 10 to 20% of total HVAC air flow
Minimum AC SEER is 13
Energy expense savings for 1 SEER unit increase: 7%
EER = SEER * 0.9
SEER values for existing systems range from 13 (inefficient) to 26 (high efficiency)
Energy savings for each degree F increase in AC cooling setting: 2%
Energy savings for each degree F decrease in heater setting: 3%
Sources of heat gain: sun radiation through windows can be huge source (in Las Vegas, home orientation alone can change AC size by over a ton, e.g. putting windows on south side versus north side)
Windows account for 40% of heat loss/gain in a typical house
1 kW lighting or equipment = 3413 BTU/hour
1 person = 250 BTU/hour
1 HP motor = 2545 BTU/hour
office equipment = 0.85 to 8.5 BTU/hour per square foot
AC system sizing:
Building type: Square Feet/ton:
Conference rooms, arenas 150-200
Classrooms 200
Industrial 300
Office/retail 350-450
Residential (typical) 600-800
Residential (high efficiency) up to 1600
Insulation:
R-8 Best double pane windows, best duct insulation
R-11 3.5 inch fiberglass insulation
R-13 Poorly insulated wall
R-19 6 inch fiberglass insulation
Lighting Loads
.5-1.0 WATTS/SF LOW – HALLWAYS, VERY EFFICIENT BUILDINGS
1.5-2.0 WATTS/SF MEDIUM – TYPICAL OFFICE BUILDINGS
2.5-3.5 WATTS/SF HIGH – LABS, TESTING, ETC.
A typical house uses 2000 kWh/year on lighting for all incandescent lamps; CFL/LED can reduce that by 60%
Lighting commonly accounts for 20% of residential energy use and 40% of commercial use
Plug-in electrical loads
.3-.5 WATTS/SF LOW – OLDER OFFICE BUILDINGS – VERY FEW Personal Computers
.5-1.0 WATTS/SF MEDIUM – TYPICAL OFFICE SPACE
1.0-1.5 WATTS/SF HIGH – DENSELY OCCUPIED OFFICES – EVERYONE WITH A P.C.
Plug loads can be up to 80% of electrical use in well-insulated homes (65% is typical)
Consumer electronics use 15% to 20% of residential energy (typical household uses 1700 kWh/year for TV, computers, etc.)
Gas/water:
California average residential gas use: 50% water heating, 40% space heating, 10% other (cooking…)
Typical hot water loads: First occupant: 20 gal/day, Next occupant: 15 gal/day, All others: 10 gal/day
Miscellaneous:
Site-to-source multiplier: 3.4 units of energy at power plant are needed for 1 unit in the home
Energy inflation: historically 6-7% (EIA usually underestimates at around 3%)
Typical Household Consumption in kWh/yr/home
Texas 14000
Ontario 10000
California 6500
Netherlands 3000
Solar:
Solar water heater can provide 60-80% of residential use
PV costs: $6-8/DCW residential, commercial/utility scale as low as $4/DCW
Payback years for solar PV and solar hot water systems of all competitive varieties are 12-14 years
Acknowledgements: information on this page came from several sources, including:
Chris Calwell, ecova.com
Gary Gerber, CalSEIA
Southern California Edison Energy Education Center
James Waltz