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You’re comparing Carnot efficiencies for heat pumps with nominal efficiencies for natural gas heaters. Heat pumps have nominal efficiencies well over 100%. They

You’re comparing Carnot efficiencies for heat pumps with nominal efficiencies for natural gas heaters. Heat pumps have nominal efficiencies well over 100%. They can move more joules of heat from outside than the number of joules of energy they consume.

hunterb123 5y ago
The efficiency depends on the temp. outside. That's why nat. gas is used for heating more in the north and less so in the south. At a certain point it's more efficient to burn the gas directly. https://en.wikipedia.org/wiki/Coefficient_of_performance https://en.wikipedia.org/wiki/Coefficient_of_performance
- johncolanduoni 5y ago
  Unless you’re heating your house in the arctic, a modern heat pump is still going to have a nominal efficiency well over 100%. So if you’re claiming your heat pump numbers above are nominal efficiencies, I’m really curious as to where you’re getting them.
  - hunterb123 5y ago
    It's a simple formula, the CoP, I linked it in my above post. The below PDF has a chart of temps to efficiencies. 47F will be around 100% efficiency or a CoP of 1. New York winter days are generally below that. https://www.energy.gov/sites/prod/files/2017/04/f34/2_32219_Shen_031417-0900.pdf https://www.energy.gov/sites/prod/files/2017/04/f34/2_32219_... That's a potential 40% energy loss. 20% at the plant, 20% at the house. It all depends on the region's temperature. Electric heating is more efficient in some places, less efficient in some, and equal in some. For New York, it does not make sense to use a heat pump: https://www.currentresults.com/Weather/New-York/Places/new-york-city-temperatures-by-month-average.php https://www.currentresults.com/Weather/New-York/Places/new-y...
    - johncolanduoni 5y ago
      That document lists the COP for an electric heat pump with an external temperature between 35F and 40F at around 3.25. The definition from the article you linked defines COP as “ ratio of useful heating or cooling provided to work (energy) required”. So at that temperature range, it’s still heating more than it’s consuming energy. A natural gas space heater cannot exceed a coefficient of performance of 1 (it would violate energy conservation). You’re still not comparing the same types of efficiencies, they have different denominators.

hunterb123 5y ago

The efficiency depends on the temp. outside. That's why nat. gas is used for heating more in the north and less so in the south. At a certain point it's more efficient to burn the gas directly. https://en.wikipedia.org/wiki/Coefficient_of_performance https://en.wikipedia.org/wiki/Coefficient_of_performance

johncolanduoni 5y ago
Unless you’re heating your house in the arctic, a modern heat pump is still going to have a nominal efficiency well over 100%. So if you’re claiming your heat pump numbers above are nominal efficiencies, I’m really curious as to where you’re getting them.
- hunterb123 5y ago
  It's a simple formula, the CoP, I linked it in my above post. The below PDF has a chart of temps to efficiencies. 47F will be around 100% efficiency or a CoP of 1. New York winter days are generally below that. https://www.energy.gov/sites/prod/files/2017/04/f34/2_32219_Shen_031417-0900.pdf https://www.energy.gov/sites/prod/files/2017/04/f34/2_32219_... That's a potential 40% energy loss. 20% at the plant, 20% at the house. It all depends on the region's temperature. Electric heating is more efficient in some places, less efficient in some, and equal in some. For New York, it does not make sense to use a heat pump: https://www.currentresults.com/Weather/New-York/Places/new-york-city-temperatures-by-month-average.php https://www.currentresults.com/Weather/New-York/Places/new-y...
  - johncolanduoni 5y ago
    That document lists the COP for an electric heat pump with an external temperature between 35F and 40F at around 3.25. The definition from the article you linked defines COP as “ ratio of useful heating or cooling provided to work (energy) required”. So at that temperature range, it’s still heating more than it’s consuming energy. A natural gas space heater cannot exceed a coefficient of performance of 1 (it would violate energy conservation). You’re still not comparing the same types of efficiencies, they have different denominators.