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> What's the average monthly leccy bill in Phoenix during the summer? $400? The average high temperature in Phoenix in July is 106.5F (41.4C). If you are cooli

> What's the average monthly leccy bill in Phoenix during the summer? $400? The average high temperature in Phoenix in July is 106.5F (41.4C). If you are cooling to 70.0F (21.1C), that's a difference of 36.5F (20.3C). The average January low in Berlin is 28.0F (-2.2C). If you are heating to 65.0F (18.3C), that's a difference of 37.0F (20.5C). I feel like many people living in climates that don't require air conditioning have this view that it's fantastically inefficient and wasteful. Depending on how you are heating (e.g. if you are using a gas boiler), cooling can be significantly more efficient per degree of difference. Especially if you don't have to dehumidify the air, as in Phoenix.

meetingthrower 2y ago
100%. And can be wonderfully done by efficient heatpumps that cover the warmer months too. Also nice correlation between hot and sunny areas which means solar can get you to net zero pretty quick. (Says man looking at his solar panels right now covered with snow.)
phaedrus441 2y ago
This is such an interesting perspective that I've never thought about. Thanks!
avianlyric 2y ago
You’re ignoring one critical difference between these two scenarios. Humans, and all human related activities, produce heat as a waste product. It’s much easier, and consumes less additional energy, to heat an occupied space, than to cool it. Thanks to the fact that your average human produces 80W of heat just to stay alive. So every human in your cold space is 80W fewer watts of energy you need to produce to heat the space. But in a hot space, it’s an extra 80W that needs to be removed. Add to that all of the appliances in a home. It’s not unusual for a home to be drawing 100W of electricity just keep stuff powered on in standby, and that’s another 100W of “free” heating. All of this is before we get to big ticket items, like hobs, ovens, water heaters etc. So cooling a living space is always more costly than heating a living space. Simply because all the waste energy created by people living in the space reduces the total heating requirement of the space, but equally increases the cooling requirement of that same space. All of this is ignoring the fact that it’s easy to create a tiny personal heated environment around an individual (it’s called a woolly jumper). But practically impossible to create a cool individual environment around a person. So in cold spaces you don’t have to heat everything up to same temperature for the space to be perfectly liveable, but when cooling a space, you have to cool everything, regardless of if it’ll impact the comfort of the occupants.
- mbesto 2y ago
  I also point out that Phoenix's "summer" last longer than Berlin's winter: https://weatherspark.com/y/75981/Average-Weather-in-Berlin-Germany-Year-Round https://weatherspark.com/y/75981/Average-Weather-in-Berlin-G... https://weatherspark.com/y/2460/Average-Weather-in-Phoenix-Arizona-United-States-Year-Round https://weatherspark.com/y/2460/Average-Weather-in-Phoenix-A...
  - dsr_ 2y ago
    The figure you are looking for is heating/cooling degree-days. For each day, use the average high and the average low. Subtract the desired maximum dwelling temperature from the average high: if the result is positive, add it to the cooling degree-days total. Subtract the average low from the from the minimum dwelling temperature: if the result is positive, add it to the heating degree-days total. Over a year, that gives you comparable figures on how much you will need to cool or heat the space. Many agencies calculate this for specific areas. Here, for example, are the current season numbers for Boston: https://www.massenergymarketers.org/resources/degree-days/boston/ https://www.massenergymarketers.org/resources/degree-days/bo... Generic regional numbers for the US: https://www.eia.gov/energyexplained/units-and-calculators/degree-days.php https://www.eia.gov/energyexplained/units-and-calculators/de...
- szvsw 2y ago
  A lot of what you said is intuitively/directionally correct, but misses a lot of important physics related to heat transfer in buildings and operational questions of space heating equipment. This is your most accurate/relevant point: > All of this is ignoring the fact that it’s easy to create a tiny personal heated environment around an individual (it’s called a woolly jumper). Whereas this is plainly wrong: > It’s much easier, and consumes less additional energy, to heat an occupied space, than to cool it. And then the following is correct but the marginal reduction in load is minimal except in relatively crowded spaces (or spaces with very high equipment power densities): > Thanks to the fact that your average human produces 80W of heat just to stay alive. The truth is it is generally easier to cool not heat when you take into account the necessary energy input to achieve the desired action on the psychrometric chart, assuming by “ease” you mean energy (or emissions) used, given that you are operating over a large volume of air - which does align with your point about the jumper to be fair! Generally speaking, an A/C uses approx. 1 unit of electricity for every 3 units of cooling that it produces since it uses heat transfer rather than heat generation (simplified ELI5). It is only spending energy to move heat, not make it. On the other hand, a boiler or furnace or resistance heat system generally uses around 1 unit of input energy for every 0.8-0.9 units of heating energy produced. Heat pumps achieve similar to coefficients of performance as A/Cs, because they are effectively just A/Cs operating in reverse. Your point about a jumper is great, but there are local cooling strategies as well (tho not as effective), eg using a fan or an adiabatic cooling device (eg a mister in a hot dry climate). > So cooling a living space is always more costly than heating a living space. Once you move to cost, it now also depends on your fuel prices, not just your demand and system type. For instance, in America, nat gas is so cheap, that even with its inefficiencies relative to a heat pump, if electricity is expensive heating might still be cheaper than cooling per unit of thermal demand (this is true for instance in MA, since electricity is often 3x the price of NG). On the other hand, if elec is less than 3x the cost of nat gas, then cooling is probably cheaper than heating per unit of demand, assuming you use natural gas for your heating system.
hhjinks 2y ago
Recently it was -7C where I lived. Even without heating, my indoor temp didn't go below 15C. In regions where cold temperatures are common, isolation and heat retaining materials are very common. Is preventing heat gain as simple as preventing heat loss?
- flerchin 2y ago
  Yes
- twothamendment 2y ago
  Yes, insulation works both ways. My garage is unheated and insulated. If I go out there to work on something in the winter I always compare the temperature outside. On a sunny day it might be pleasant outside and freezing in my garage - so I'll open the door and let it warm up. Insulation makes the house more resistance to temperature change (relative to the inside and outside). One thing people forget is the delta is very different in the summer and winter. Lets say your thermostat is on 70 year round. If it is 100 degrees out you only have to cool 30 degrees. When it is 0 F out you have a delta of 70 degrees. So for this scenario, expect to use more energy in the winter.
currymj 2y ago
you cannot win this argument with the average person who lives in a chilly European country. it just does not compute. there are whole important cultural lifeways related to opening and closing windows at proper times for efficient cooling and ventilation. these work really well — in Europe — and are treasured traditions. getting people to accept AC is sort of like trying to convince the average American to go grocery shopping on a bicycle. some may accept the idea but only the most European influenced already.
- llamaimperative 2y ago
  There's a big gap between "accept AC" and "build a megapolis in a city named after a bird that bursts into flames." Phoenix is a slow-rolling disaster regardless of whether it's easier to heat or cool a room to comfort.
noqc 2y ago
a greenhouse can heat a space by enough to be comfortable for free, but not cool it. Windows and sunlight matter.

meetingthrower 2y ago

100%. And can be wonderfully done by efficient heatpumps that cover the warmer months too. Also nice correlation between hot and sunny areas which means solar can get you to net zero pretty quick. (Says man looking at his solar panels right now covered with snow.)

phaedrus441 2y ago

This is such an interesting perspective that I've never thought about. Thanks!

avianlyric 2y ago

You’re ignoring one critical difference between these two scenarios. Humans, and all human related activities, produce heat as a waste product. It’s much easier, and consumes less additional energy, to heat an occupied space, than to cool it. Thanks to the fact that your average human produces 80W of heat just to stay alive. So every human in your cold space is 80W fewer watts of energy you need to produce to heat the space. But in a hot space, it’s an extra 80W that needs to be removed. Add to that all of the appliances in a home. It’s not unusual for a home to be drawing 100W of electricity just keep stuff powered on in standby, and that’s another 100W of “free” heating. All of this is before we get to big ticket items, like hobs, ovens, water heaters etc. So cooling a living space is always more costly than heating a living space. Simply because all the waste energy created by people living in the space reduces the total heating requirement of the space, but equally increases the cooling requirement of that same space. All of this is ignoring the fact that it’s easy to create a tiny personal heated environment around an individual (it’s called a woolly jumper). But practically impossible to create a cool individual environment around a person. So in cold spaces you don’t have to heat everything up to same temperature for the space to be perfectly liveable, but when cooling a space, you have to cool everything, regardless of if it’ll impact the comfort of the occupants.

mbesto 2y ago
I also point out that Phoenix's "summer" last longer than Berlin's winter: https://weatherspark.com/y/75981/Average-Weather-in-Berlin-Germany-Year-Round https://weatherspark.com/y/75981/Average-Weather-in-Berlin-G... https://weatherspark.com/y/2460/Average-Weather-in-Phoenix-Arizona-United-States-Year-Round https://weatherspark.com/y/2460/Average-Weather-in-Phoenix-A...
- dsr_ 2y ago
  The figure you are looking for is heating/cooling degree-days. For each day, use the average high and the average low. Subtract the desired maximum dwelling temperature from the average high: if the result is positive, add it to the cooling degree-days total. Subtract the average low from the from the minimum dwelling temperature: if the result is positive, add it to the heating degree-days total. Over a year, that gives you comparable figures on how much you will need to cool or heat the space. Many agencies calculate this for specific areas. Here, for example, are the current season numbers for Boston: https://www.massenergymarketers.org/resources/degree-days/boston/ https://www.massenergymarketers.org/resources/degree-days/bo... Generic regional numbers for the US: https://www.eia.gov/energyexplained/units-and-calculators/degree-days.php https://www.eia.gov/energyexplained/units-and-calculators/de...
szvsw 2y ago
A lot of what you said is intuitively/directionally correct, but misses a lot of important physics related to heat transfer in buildings and operational questions of space heating equipment. This is your most accurate/relevant point: > All of this is ignoring the fact that it’s easy to create a tiny personal heated environment around an individual (it’s called a woolly jumper). Whereas this is plainly wrong: > It’s much easier, and consumes less additional energy, to heat an occupied space, than to cool it. And then the following is correct but the marginal reduction in load is minimal except in relatively crowded spaces (or spaces with very high equipment power densities): > Thanks to the fact that your average human produces 80W of heat just to stay alive. The truth is it is generally easier to cool not heat when you take into account the necessary energy input to achieve the desired action on the psychrometric chart, assuming by “ease” you mean energy (or emissions) used, given that you are operating over a large volume of air - which does align with your point about the jumper to be fair! Generally speaking, an A/C uses approx. 1 unit of electricity for every 3 units of cooling that it produces since it uses heat transfer rather than heat generation (simplified ELI5). It is only spending energy to move heat, not make it. On the other hand, a boiler or furnace or resistance heat system generally uses around 1 unit of input energy for every 0.8-0.9 units of heating energy produced. Heat pumps achieve similar to coefficients of performance as A/Cs, because they are effectively just A/Cs operating in reverse. Your point about a jumper is great, but there are local cooling strategies as well (tho not as effective), eg using a fan or an adiabatic cooling device (eg a mister in a hot dry climate). > So cooling a living space is always more costly than heating a living space. Once you move to cost, it now also depends on your fuel prices, not just your demand and system type. For instance, in America, nat gas is so cheap, that even with its inefficiencies relative to a heat pump, if electricity is expensive heating might still be cheaper than cooling per unit of thermal demand (this is true for instance in MA, since electricity is often 3x the price of NG). On the other hand, if elec is less than 3x the cost of nat gas, then cooling is probably cheaper than heating per unit of demand, assuming you use natural gas for your heating system.

hhjinks 2y ago

Recently it was -7C where I lived. Even without heating, my indoor temp didn't go below 15C. In regions where cold temperatures are common, isolation and heat retaining materials are very common. Is preventing heat gain as simple as preventing heat loss?

flerchin 2y ago
Yes
twothamendment 2y ago
Yes, insulation works both ways. My garage is unheated and insulated. If I go out there to work on something in the winter I always compare the temperature outside. On a sunny day it might be pleasant outside and freezing in my garage - so I'll open the door and let it warm up. Insulation makes the house more resistance to temperature change (relative to the inside and outside). One thing people forget is the delta is very different in the summer and winter. Lets say your thermostat is on 70 year round. If it is 100 degrees out you only have to cool 30 degrees. When it is 0 F out you have a delta of 70 degrees. So for this scenario, expect to use more energy in the winter.

currymj 2y ago

you cannot win this argument with the average person who lives in a chilly European country. it just does not compute. there are whole important cultural lifeways related to opening and closing windows at proper times for efficient cooling and ventilation. these work really well — in Europe — and are treasured traditions. getting people to accept AC is sort of like trying to convince the average American to go grocery shopping on a bicycle. some may accept the idea but only the most European influenced already.

llamaimperative 2y ago
There's a big gap between "accept AC" and "build a megapolis in a city named after a bird that bursts into flames." Phoenix is a slow-rolling disaster regardless of whether it's easier to heat or cool a room to comfort.

noqc 2y ago

a greenhouse can heat a space by enough to be comfortable for free, but not cool it. Windows and sunlight matter.