Avoided Emissions Calculation Disclaimer

All emissions reductions from renewable energy projects are determined by comparison with the New England generator fleet, because that is where the energy will be displaced.  This produces results that may be significantly different from emissions savings based on a comparison to national averages, as is done in the “Fat Spaniel” remote data monitoring system.  For example, the percentage of electric energy generated by coal in the United States is 46%.  In New England, the percentage is only 15%.  Since coal contributes 77% more carbon dioxide per MWh of energy generated than natural gas, renewable energy systems in New England will show more modest emission reductions than the same system would in Ohio, for instance. 


In addition, the generation characteristics of each technology have an impact on the emissions reduction that can be expected.  Solar-powered systems will produce only during the daylight hours, which normally coincides with the peak demand period for the utilities.  The generating fleet during this time may include peaking plants and reserve plants, which will have lower efficiencies than the “baseload” plants which run 24 hours per day.  Consequently, emissions are higher, and the renewable energy systems look better by comparison.  Wind and hydro plants, on the other hand, are much less predictable on an hourly basis, and may have significant seasonal variations. Consequently, we have assumed, as a first approximation, that the appropriate comparison is to the “Annual Average (all hours) Marginal Emissions Rate”.


The emission reduction calculations for CCEF are based on the results of the 2004 New England Marginal Emission Rate Analysis reflect the following assumptions:

  • PV systems are analyzed using the average of the Marginal Emission Rates (in Lbs/MWh) for “On-Peak Ozone Season” and “On-Peak Non-Ozone Season”.  The underlying assumptions are that PV systems will be operating primarily during the on-peak periods, and that their output in the five months of the “Ozone Season” (May – September) is about the same as in the seven months of the “Non-Ozone Season.” 
  • Wind and micro-hydro are evaluated using the “Annual Average (all hours) Marginal Emission Rates”, on the assumption that the output from these systems is somewhat random, and distributed fairly evenly over all of the categories during the course of a year. 
  • Biomass and fuel cells are also evaluated using the “Annual Average (all hours) Marginal Emission Rates”, because they are expected to produce power continually as “base load” generators.  We don’t have biomass on the table because each biomass installation may have unique emission characteristics, and because we haven’t seen any biomass projects in the On-Site Renewable DG program, yet. 
  • Fuel Cell emissions are based on the assumption that 50% of the thermal output (“waste heat”) is used to displace natural gas used for heating.  This is very conservative, since 50% thermal utilization is the minimum standard for CCEF’s acceptance of a fuel cell project.