Of the 106 million housing units in the U.S, 19 million, or 18 percent, are multi-family. In the Gulf Coast Region, there were about 10.3 million housing units in 2005, of which 1.7 million were defined as multi-family units defined as buildings with five or more units as defined by HUD (approximately 16% of total housing in the region). Table 1 below describes all multi-family housing in the Gulf Coast Region.1
Table 1. Total Number of Multi-Family Housing Units in the Gulf Coast Region, 2005
| Louisiana |
1,656,053 |
165,818 |
10% |
| Oklahoma |
1,342,293 |
136,779 |
10% |
| Texas |
7,393,354 |
1,376,363 |
19% |
Source: "Energy Efficiency in Multi-Family Housing: A Profile and Analysis," by
Matthew Brown and Mark Wolfe, June 2007 (Appendix A-1)
Nationally, multi-family buildings are, for the most part, occupied by renters. This trend is echoed in the Gulf Coast Region as well, with 94% of all multi-family housing units occupied by renters as shown in Table 2.1
Table 2. Multi-Family Housing in the Gulf Coast Region - Renters and Owners, 2000
| Louisiana |
155,151 |
1.0% |
10,667 |
0.3% |
| Oklahoma |
131,246 |
0.8% |
5,533 |
0.2% |
| Texas |
1,304,817 |
8.2% |
71,546 |
2.2% |
Source: "Energy Efficiency in Multi-Family Housing: A Profile and Analysis," by
Matthew Brown and Mark Wolfe, June 2007 (Appendices B-2 and B-3)
Energy Use Characteristics
The amount of energy used in multi-family buildings varies, depending on their condition, age, original design, or controls and policies - such as whether tenants in rental buildings pay their utility bills as part of their rent or pay it separately based on their energy use. Overall, residential housing accounts for 22 percent of energy use in the United States. Of that amount, 72 percent is accounted for by single-family housing and 28 percent by multi-family (more than 2 units).1
On whole, multi-family buildings tend to be less energy intensive than single-family homes, as shown in Figure 1. The reasons for this difference are the comparatively smaller wall and roof space and the smaller size of units within multi-family buildings.1
Current Status
In 2005, installed CHP capacity in apartment buildings was estimated to be 70.4 MW at 150 sites across the U.S.3 Overall, natural gas is the most common fuel used in these systems. Reciprocating engines, fuel cells and micro-turbines are the most common prime movers used.
Future CHP Potential in the United States
In 2005, the potential for additional CHP in apartment buildings was estimated at 11,600 MW nationally.3 The table below shows the breakdown of this potential by both CHP system size and number of apartment buildings.
Table 4. CHP Potential in the U.S. Apartments Market Sector, 2005
| CHP System Size |
150 kW |
500 kW |
1,500 kW |
| Apartments/Building |
100-200 |
200-500 |
>500 (avg 875) |
| Private* |
19,804 |
12,084 |
1,030 |
| Public** |
2,322 |
1,100 |
95 |
| Total # of Buildings |
22,126 |
13,184 |
1,125 |
Source: Bruce Hedman, "Multi-Family Housing: An Underserved Market
for Combined Heat and Power," EEA, Inc. Sept 19, 2005
Is My Multi-Family Building a Good Candidate for CHP?
Residential cogeneration systems work best in large buildings with heavy power demands. The buildings with the highest potential for energy savings are multi-family dwellings (approximately 100 apartments or more) that have high electrical and heating usage for 16 hours a day or more, six days a week.2
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General Guidelines for CHP Projects in a Multi-Family Building
- Does the building contain at least 100 units?
The economics for installing CHP currently favor buildings containing at least 100 dwelling units, but there are examples of installations in smaller buildings. Buildings that share a common boiler room can each be smaller in size (less than 150 dwelling units) and still benefit from CHP.
- Is the building's electric load master-metered/sub-metered?
A residential building that is master-metered or sub-metered by an electric utility can be a good candidate for CHP since the electric load of each apartment as well as the building's common areas (as well as the thermal load) is available to the CHP system.
- Does the building consume at least 50,000 kWh of electricity per month?
- Does the building consume at least 30,000 CCF of natural gas per year?
- Does the building contain a central laundry or pool?
- Does the building use a hot water (hydronic) or steam space-heating system?
- Does the building's existing HVAC system need to be upgraded or replaced soon?
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Case Studies