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“Electrical devices can sometimes offer higher than 100% efficiency,” said BNEF analyst Matthias Kimmel. That might seem odd. How can there be more energy as ou

“Electrical devices can sometimes offer higher than 100% efficiency,” said BNEF analyst Matthias Kimmel. That might seem odd. How can there be more energy as output than input? But that’s exactly what heat pumps and air conditioners do. They use electricity to shift heat from the outside to inside, or vice-versa, and typically provide three units of energy service for one unit of energy input, meaning an efficiency of 300%." Article seems to arguing against basic thermodynamic laws. Air conditioners and heat pumps do not output more energy than they consume. You can't move heat around without expending lots of energy. I'm suspicious this is just uptalk trying convince people renewables can replace fossil fuels without any new data, just confusing lines of arguments.

xboxnolifes 6y ago
This came up in the last hackernews post I've seen on the topic. It essentially boiled down to that air conditioner efficiency (and similar machines) is measured using a different formula than energy conversion efficiency.
- Gibbon1 6y ago
  In one case your are calculating efficiency in terms of unit of work per unit of energy in. The other you are looking at the efficiency in term of unit of heat per unit of energy.
serpix 6y ago
well my 80m2 apartment is fully heated to about 22.5C with an air heat pump drawing about 600W with an outside temperature of 0C. So take from that what you will about efficiency.
- alacombe 6y ago
  That's no particular feat, you can heat a forge to 1200C with enough insulation and just 600W. Also, this is just considering a limited referential, ie. the one impacting the most your wallet. If you consider a bigger referential, your efficiency will drop below 1 for sure. Not to mention that your system will leak refrigerant (it's really not a matter of "if" but "when"), which is likely to have greenhouse effects.
deleted 6y ago
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eulers_secret 6y ago
Moving heat does take energy, true. A restive electric heater (AKA joule heating) is by definition 100% efficient: All energy consumed by the device is turned into heat (if you're mega-pedantic, you could argue some is lost as light and sound). A heat pump just moves heat from outside to inside. Sure, it's 42*F out, but that's still heat energy that can be moved. This process is more efficient than converting electricity into heat because you get more heat energy in the room than the electric energy you put into the device. https://en.wikipedia.org/wiki/Joule_heating#Heating_efficiency https://en.wikipedia.org/wiki/Joule_heating#Heating_efficien... explains it even better than I did.
colechristensen 6y ago
> Air conditioners and heat pumps do not output more energy than they consume. They absolutely do. A heat pump will output more heat where it is wanted than would be output by flowing the electricity through a big resistor. You put 100 W into a heat pump and you can get 300 W of heat out. You are not cheating thermodynamics, but using energy to move energy.

xboxnolifes 6y ago

This came up in the last hackernews post I've seen on the topic. It essentially boiled down to that air conditioner efficiency (and similar machines) is measured using a different formula than energy conversion efficiency.

Gibbon1 6y ago
In one case your are calculating efficiency in terms of unit of work per unit of energy in. The other you are looking at the efficiency in term of unit of heat per unit of energy.

serpix 6y ago

well my 80m2 apartment is fully heated to about 22.5C with an air heat pump drawing about 600W with an outside temperature of 0C. So take from that what you will about efficiency.

alacombe 6y ago
That's no particular feat, you can heat a forge to 1200C with enough insulation and just 600W. Also, this is just considering a limited referential, ie. the one impacting the most your wallet. If you consider a bigger referential, your efficiency will drop below 1 for sure. Not to mention that your system will leak refrigerant (it's really not a matter of "if" but "when"), which is likely to have greenhouse effects.

deleted 6y ago

[deleted]

eulers_secret 6y ago

Moving heat does take energy, true. A restive electric heater (AKA joule heating) is by definition 100% efficient: All energy consumed by the device is turned into heat (if you're mega-pedantic, you could argue some is lost as light and sound). A heat pump just moves heat from outside to inside. Sure, it's 42*F out, but that's still heat energy that can be moved. This process is more efficient than converting electricity into heat because you get more heat energy in the room than the electric energy you put into the device. https://en.wikipedia.org/wiki/Joule_heating#Heating_efficiency https://en.wikipedia.org/wiki/Joule_heating#Heating_efficien... explains it even better than I did.

colechristensen 6y ago

> Air conditioners and heat pumps do not output more energy than they consume. They absolutely do. A heat pump will output more heat where it is wanted than would be output by flowing the electricity through a big resistor. You put 100 W into a heat pump and you can get 300 W of heat out. You are not cheating thermodynamics, but using energy to move energy.