Appendix B: Energy Supply and Use in Cambridge
The discussion of energy efficiency potential must be informed by a clear picture of not only how much energy is currently demanded, but when and how it is used. This section provides this basic information, and is summarized in the following table and list:
Table 14. Overview Energy Statistics
| Cambridge Energy Statistics | |
|---|---|
| Annual electricity consumption (2006) | 1.8 million MWh |
| Peak demand (2006) | 370 MW |
| ESTIMATED gasoline consumption for personal vehicles (gallons/year) | 22 million gallons |
- Cambridge has few local generation resources; electricity comes from the New England regional grid;
- Natural gas and nuclear plants provide >55% of the region’s annual energy;
- The average carbon intensity of its energy is 0.1 metric tons carbon-equivalent per megawatthour (MTCE/MWh), or 0.4 short tons CO2-equivalent per MWh (tCO2e/MWh);
- Approximately 1,600 megawatts (MW) of the region’s load are available for demand response (~5.7% of historical peak demand); and
- Existing supply projected to fall short of demand in Boston area by 2014.
The Regional System’s Fuel Mix
Over 90% of the electricity consumed in Cambridge comes from the New England regional grid. In 2004, over half of the energy generated within this region came from nuclear and natural gas-fired power plants (see Figure 2). The region’s reliance on gas is a source of concern, according to Independent System Operator (ISO) New England’s 2005 Regional System Plan. Gas price volatility is high, and during winter months when heating increases the demand for gas, the lack of fuel diversity could be a risk to reliable electric supply.
New England Installed Capacity and Sources of Energy (Click image to view full size)
The region’s average carbon intensity in 2002 was 0.1 MTCE/MWh (0.4 tCO2e/MWh) of electricity generated. For comparison, the carbon intensity of direct natural gas use is 0.014 MTCE (0.058 tCO2e) per million Btu.
Supply Infrastructure
The ISO projects peak demand in New England to grow by 1.5% annually, and electricity consumption to grow by ~1.1% annually in the greater Boston area. Existing peaking capacity is projected to be insufficient to meet demand in the greater Boston area by 2014, and the ISO describes transmission infrastructure to import more as “limited.” Therefore, costly upgrades to infrastructure will be needed, or efficiency must be improved to reduce this growth.
Energy Efficiency
Energy efficiency programs run by utilities in the New England region have achieved savings of approximately 8,000 GWh per year, along with 1,600 MW of controllable load (see Table 15). NSTAR, the delivery utility for Cambridge, currently offers efficiency programs for both gas and electricity, and for both residences and businesses. In addition, NSTAR offers a load response program to its business customers. A list of these programs is included in Appendix C.
Table 15: Demand Response and Efficiency Savings Achieved in New England
| Year | Summer Peak Demand Response (MW) | Energy (GWh/yr) |
|---|---|---|
| 2004 | 1,507 | 7,590 |
| 2005 | 1,552 | 7,909 |
| 2006 | 1,603 | 8,078 |
| Avg forecast 2007-2014 | 1,597 | 8,205 |
Renewable Energy
Massachusetts currently has approximately 837 MW of installed renewable energy (see Table 16) capacity that has been approved as counting towards the state’s renewable portfolio standard (RPS). See “Regulatory and Policy Context for Cambridge” for more on Massachusetts’ RPS.
Table 16: Units Qualifying for Massachusetts RPS
| Technology | Nameplate Capacity (MW) |
|---|---|
| Anerobic Digester | 20 |
| Biomass | 204 |
| Landfill Gas | 133 |
| Photovoltaic | 2 |
| Wind | 478 |
| Total | 837 MW |
Energy Use
Summary
- NEEP’s 2005 study identified significant potential for increasing the efficiency of energy use;
- Fuel oil used for heating is a significant contributor to Cambridge’s CO2 emissions; and
- Targeted 50 MW peak demand reduction is 13.5% of Cambridge’s 2006 peak (370 MW).
Electricity use in the Boston system sub-area is projected to grow by an average of 1.17% through 2014 (for comparison, the expected growth rate for the full New England region is 1.44%).
The division of energy use by major sector across Massachusetts is shown in Figure 3.23 Figure 3 shows RMI’s approximation of total energy consumed within Cambridge, by type of energy. Further information on electric rates is available in Appendix D.
Figure 3: Massachusetts Energy Use by Sector (2001)
Figure 4: Estimate of Cambridge Energy Use
Energy Use for Transportation
Table 17 shows the estimated number of cars per family in Cambridge, approximately 41,000. Using the Energy Information Administration (EIA)’s value of 535 gallons of fuel per year, per car, annual gasoline consumption in Cambridge is approximately 22 million gallons, or 2.75 million MMBtu per year. This is approx. 1/2 the total electrical energy consumed in Cambridge in 2006.
Personal vehicles are not the only way in which energy is used in the transportation sector. While Cambridge-specific data was unavailable, Figure 5 shows the breakdown of transportation-related energy end uses for all of New England.
Table 17: Vehicles available per residence in Cambridge
| Vehicles per household | # of households |
|---|---|
| No vehicles available | 12,608 |
| 1 vehicle available | 21,367 |
| 2 vehicles available | 5,677 |
| 3 or more vehicles available | 1,324 |
| Total vehicles = 41,000 | |
Figure 5: Transportation Energy End Uses (New England)
Energy Use for Buildings
Cambridge’s 2006 monthly peak demand and electricity consumption values are shown in Figure 6. Peak demand occurs during the summer, when air conditioning systems face high temperatures and humidity. Figure 6 also shows the Cambridge Energy Alliance’s targeted 50 MW reduction, which in 2006 would have yielded a peak of 320 MW.
Figure 6: Cambridge Electricity and Demand, 2006 (Click image to view full size)
Fuels for Heating
New England is unusual within the United States for the relatively high percentage of buildings heated with fuel oil (25% of commercial sector buildings, 14% of residences). The burning of fuel oil emits considerably more greenhouse gases (CO2) and local pollutants (NOx and SOx) than does the burning of natural gas (see Table 18).
Table 18: Heating Fuel Use and Emissions Comparison
| Heating fuel use in Cambridge’s commercial sector | |
|---|---|
| Electric | 5% |
| Natural Gas | 69.7% |
| Fuel Oil | 25.3% |
| Heating fuel use in Cambridge’s residential sector | |
|---|---|
| Utility gas | 67% |
| Bottled, tank, or LP gas | 3% |
| Electricity | 14% |
| Fuel oil, kerosene, etc. | 14% |
| Coal or coke | 0% |
| Wood | 0% |
| Solar energy | 0% |
| Other fuel | 1% |
| No fuel used | 1% |
| Fossil Fuel Emission Levels (pounds per MMBtu output) | ||
|---|---|---|
| Pollutant | Natural Gas | Oil |
| CO2 | 117 | 164 |
| CO | 40 | 33 |
| NOx | 92 | 448 |
| SOx | 1 | 1,122 |
Residential Sector
The residential building stock in Cambridge is notable for its large numbers of multi-family buildings and for the high percentage of pre-1940 construction. Table 19 and Table 20 describe the residential building stock by size and number of buildings, and construction year.
Table 19: Cambridge residential buildings
| Dwelling Type | Number of Buildings | Total sq. footage |
|---|---|---|
| Residential Single unit | 3,960 | 8,712,454 |
| Residential 2-4 units | 5,096 | 16,294,463 |
| Residential >8 units | 11,990 | 29,630,774 |
| Total | 21,046 | 54,637,691 |
Table 20: Age of Cambridge Residential Buildings
| Cambridge residential buildings Year structure built | |
|---|---|
| Built 2005 or later | 1% |
| Built 2000 to 2004 | 5% |
| Built 1990 to 1999 | 5% |
| Built 1980 to 1989 | 7% |
| Built 1970 to 1979 | 5% |
| Built 1960 to 1969 | 7% |
| Built 1950 to 1959 | 3% |
| Built 1940 to 1949 | 4% |
| Built 1939 or earlier | 63% |
| Total | 45,006 |
While space heating consumes over half of total residential sector energy in New England, Figure 7 shows that electricity use is distributed nearly evenly amongst a several end uses, with refrigeration and other kitchen appliances comprising a total of 32% of residential energy in New England. While air conditioning consumes only 7% of annual electrical energy, it is the primary driver of summer demand peak in the region.
Figure 7: Residential Electricity End Use Breakdown
Commercial Sector
A detailed breakdown of Cambridge’s commercial building types was not available, but Figure 8 gives the overall breakdown of energy use within all building types across New England. The charts below provide total energy end use breakdowns for major commercial building types for Cambridge’s climate zone. A more detailed breakdown of commercial end-use demand is in Appendix F.
Figure 8: Commercial Energy End Use Breakdown (New England)
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