A major purpose of any energy audit is to determine where energy waste occurs. With this information in hand, the energy auditor then allocates resources according to the energy-savings potential of each energy-conservation measure. A solid understanding of how homes use energy should guide the decision-making process.
|
Energy User |
Annual kWh |
Annual Therms |
|---|---|---|
|
Heating |
2000–10,000 |
200–1100 |
|
Cooling |
600–7000 |
n/a |
|
Water Heating |
2000–7000 |
150–450 |
|
Refrigerator |
500–2500 |
n/a |
|
Lighting |
500–2000 |
n/a |
|
Clothes Dryer |
500–1500 |
n/a |
|
Estimates by the authors from a variety of sources. |
||
We divide home energy usage into two categories: baseload and seasonal. Baseload includes water heating, lighting, refrigerator, and other appliances used year round. Seasonal energy use includes heating and cooling. You should understand which of the two is dominant as well as which types of baseloads and seasonal loads are the highest energy consumers.
Many homes are supplied with both electricity and at least one source of combustion fuel. Electricity can provide all seasonal and baseload energy, however most often there is a combination of electricity and natural gas, oil, or propane. The auditor must understand whether loads like the heating system, clothes dryer, water heater, and kitchen range are serviced by electricity or by fossil fuel.
Total energy use relates directly to potential energy savings. The greatest savings are possible in homes with highest initial consumption. Avoid getting too focused on a single energy-waste category. Consider all the individual energy users that offer measurable energy savings.
To separate baseload from seasonal energy consumption for a home with monthly gas and electric billing, do these steps.
1. Get the energy billing for one full year. If the customer can’t produce these bills, they can usually request a summary from their utility company.
2. Add the 3 lowest bills together.
3. Divide that total by 3.
4. Multiply this three-month low-bill average by 12. This is the approximate annual baseload energy cost.
5. Total all 12 monthly billings.
6. Subtract the annual baseload cost from the total billings. This remainder is the space heating and cooling cost.
7. Heating is separated from cooling by looking at the months where the energy is used — summer for cooling, winter for heating.
8. For cold climates, add 5 to 15 percent to the baseload energy before subtracting it from the total to account for more hot water and lighting being used during the winter months.
Energy indexes are useful for comparing homes and characterizing their energy efficiency. They are used to measure the opportunity for application of weatherization or home performance work.
Most indexes are based on the square footage of conditioned floor space. The simplest indexes divide a home’s energy use in either kilowatt-hours or British thermal units (BTUs) by the square footage of floor space.
A more complex index compares heating energy use with the climate’s severity. BTUs of heating energy are divided by both square feet and heating degree days to calculate this index.
Seasonal energy use is the energy used to heat and cool our homes to maintain comfort in the house based on the season. Baseload, on the other hand, doesn't change much over the year. Baseload uses are water heating, the refrigerator, the lights, the clothes dryer, other appliances, and plug loads like TVs and computers. To analyze the client's energy consumption you have to separate their energy use into seasonal energy use and baseload energy use. In this lesson we'll learn to separate gas into heating and baseload, and electricity into cooling and baseload. Then we'll look at how consumption and climate are related. And then finally some cost and savings information. Click here to view the lesson.