5 ms·

To an outsider, “4Wh/day” could also be expressed as “167 mW (amortized)”. Wh/day is an idiom. I think it’s strange to claim that it’s the only “right” way of e

To an outsider, “4Wh/day” could also be expressed as “167 mW (amortized)”. Wh/day is an idiom. I think it’s strange to claim that it’s the only “right” way of expressing power consumption. For a good many people outside the field, the first thing we do when we see such a figure is convert it back to its SI units so that we can do our calculations within the system that we’re more familiar with (and something like 90% of the world uses SI).

qayxc 5y ago
First of all I was talking about power consumption, which is never expressed in MW or kW. Secondly, mW is also power, not electricity consumption. 4Wh is power consumption (or electricity use if you will). The "per day"-part was just referring to the duration, hence the use of a different unit. I could just as well have used Joules and skip the "day"-part entirely to confuse the reader as to how I arrived at the final figure. Edit: just to make this even clearer - do the dimensional analysis yourself and see why I used Wh/day. Or to put it differently: what do think is the answer to the question "say a car saves 4Wh of electricity every day. How much electricity does the car save in a year?" Correct me if I'm wrong, but I'd say it saves 4Wh/d•365d = 4•365 Wh/d•d = 4•365 Wh (or 5.256 MJ if you insist). > the first thing we do when we see such a figure is convert it back to its SI units so that we can do our calculations within the system that we’re more familiar with I bet my firstborn that the vast majority of the population will not do that and are not familiar at all with the actual meaning of the figure. Had I converted the whole shebang into Joules instead and expressed the total energy savings as 5.256 Terajoule I can guarantee that outside the odd physics major no one would be familiar with what kind of energy use we're talking about. Look at your electricity bill and tell me what it unit it uses.
- wallacoloo 5y ago
  4 Wh/day = 4 W*h/(24*h) = 0.167 W. They’re equivalent, by algebra. The only way they can ever mean different things is if you use a custom algebra.
  - qayxc 5y ago
    Your solution still answers the wrong question and even results in a contradiction: the initial statement was "say there's a [power] saving of 2W." Your conclusion would be that there's a power saving of 0.167W, which in incoherent with the initial assumption. Context is very important.

qayxc 5y ago

First of all I was talking about power consumption, which is never expressed in MW or kW. Secondly, mW is also power, not electricity consumption. 4Wh is power consumption (or electricity use if you will). The "per day"-part was just referring to the duration, hence the use of a different unit. I could just as well have used Joules and skip the "day"-part entirely to confuse the reader as to how I arrived at the final figure. Edit: just to make this even clearer - do the dimensional analysis yourself and see why I used Wh/day. Or to put it differently: what do think is the answer to the question "say a car saves 4Wh of electricity every day. How much electricity does the car save in a year?" Correct me if I'm wrong, but I'd say it saves 4Wh/d•365d = 4•365 Wh/d•d = 4•365 Wh (or 5.256 MJ if you insist). > the first thing we do when we see such a figure is convert it back to its SI units so that we can do our calculations within the system that we’re more familiar with I bet my firstborn that the vast majority of the population will not do that and are not familiar at all with the actual meaning of the figure. Had I converted the whole shebang into Joules instead and expressed the total energy savings as 5.256 Terajoule I can guarantee that outside the odd physics major no one would be familiar with what kind of energy use we're talking about. Look at your electricity bill and tell me what it unit it uses.

wallacoloo 5y ago
4 Wh/day = 4 W*h/(24*h) = 0.167 W. They’re equivalent, by algebra. The only way they can ever mean different things is if you use a custom algebra.
- qayxc 5y ago
  Your solution still answers the wrong question and even results in a contradiction: the initial statement was "say there's a [power] saving of 2W." Your conclusion would be that there's a power saving of 0.167W, which in incoherent with the initial assumption. Context is very important.