15. Here's a simple tool on the EPA website. Note they use "non-baseload" factors. https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references …
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Replying to @RichardMeyerDC
16. Marginal analysis is most appropriate when evaluating changes in electricity consumption, say due to an efficiency measure.
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Replying to @RichardMeyerDC
17. Marginal analysis is also the most appropriate when evaluating gas appliances versus electric.
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Replying to @RichardMeyerDC
18. This digression was important because marginal analyses suggest efficient gas use will play a role much longer in a decarbonizing grid.
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Replying to @RichardMeyerDC
19. To illustrate: If a new gas appliance displaces some electricity, I’m not actually (generally) removing any renewables from the grid.
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Replying to @RichardMeyerDC
20. My new gas appliance *will* remove some amount of gas- or coal-fired generation - the marginal resources - from the grid.
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21. If we simply the analysis the question becomes: to use natural gas in a furnace or in a power plant (plus end-use heating appliance)?
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Replying to @RichardMeyerDC
22. In most places where homes must have heat for winter, a natural gas furnace results in less CO2 than a heat pump.
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Replying to @RichardMeyerDC
23. That's true if we assume an average grid mix, but it's especially true when we use non-baseload mixes (marginal methodologies).
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Replying to @RichardMeyerDC
At what mix is it not true? What percentage of a grid must be zero carbon for it not to be true? Something less than 100%. Thoughts?
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Assuming emissions from gas burners equal to 220 grams/kWh_heat, and given an Energy Star minimum geothermal heat pump COP of 3.6, then any Energy Star compliant heat pump will produce fewer emissions than gas whenever the grid emission rate is less than 792 grams/kWh.
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