A: You really should give up hot showers. That hot water means wasted energy, fossil fuels warming the planet, damaging ecosystems and displacing people.

B: But I like my warm showers!

A: Global warming is a huge catastrophe on the horizon, and if we want to limit the scope of the disaster we need to act. Yes, you like your showers, but people who live in low-lying villages like having their homes and land! Are you so selfish that you value this material comfort over billions of lives?

B: Surely my showers aren't costing billions of lives all on their own, though? I mean, I stay in there a little while, but billions?

A: Billions are at risk from climate change, and our wasteful first-world lifestyle is the cause. If we can get everyone's consumption down to sustainable levels then we can avert the worst of the damage.

B: How bad are my showers, really? This calculator says I use 48 therms/year, and the EPA says it's 0.005T of CO2-equivalent per therm, so that's 0.25T/year. We can avert CO2 emissions at a bit under $2/T, so offsetting my warm showers is $0.50/year. That's really not that much! Wouldn't you rather I give $5/year to fight global warming than switch to cold showers?

A: Your numbers look plausible but you're ignoring the communication value of giving up warm showers. I'm skeptical of your assessment of donations to effective charities vs. personal consumption changes because it seems to ignore many of the important effects of personal changes like signaling your disapproval of the energy system, especially when that signaling is coming from a particularly influential person (which I think the average EA is). If you tell your friends, and they follow your lead and tell their friends, we can reduce emissions a lot.

B: The per-person benefit of cold showering is still very low, and nearly everyone would prefer to donate $5/year than give up warm showers. And your donations can inspire others just as your consumption changes can. So people should donate to effective charities, and not worry about the showers.

A: I just don't understand why this is an either/or. Why does donating $5 have anything at all to do with avoiding hot showers? I know I am easily able to do both of those things and, while certainly not everyone is, I can't think of any reason why choosing one would prevent someone from choosing the other. Honestly this comparison seems pretty silly to me: we should be encouraging people, especially EA folks who understand these issues, to take fewer hot showers and donate more. I'm not a fan of minimizing the climate change effects here by comparing them to a $5 bill.

B: Say I'm trying to decide what to do next: give up hot showers or donate $5. I believe they accomplish very similar amounts of good, and I'd rather give the $5 than give up a year of showers, so I donate. Then I ask myself the question again. And again "give" seems like it will make me happier than "give up". I would have to repeat this a lot of times before I had given up so much money that in fact $5 would be painfully dear, and by that point I probably wouldn't be able to afford hot showers anyway. — I'm not saying everyone should give until another $5 would be extraordinarily painful to do without, just that unless you're pushing yourself to that point "donate another $5" does just as much good with less sacrifice than "give up hot showers".

A: People have finite donation money. I've never seen anyone other than maybe people claiming it in posts like this say they have the sort of ultra-general finite altruistic point-system that would be necessary for someone to actual face a no-showers vs. donation tradeoff. Even if this sometimes happens, I really doubt it's common enough to substantiate a general claim like, "climate change activists should be ok with hot showers".

B: Willingness to sacrifice things you enjoy for the benefit of others is a constraint. You can spend this willingness on donating more or on giving up hot showers. I'm arguing that giving up hot showers is a much less valuable way to spend it.

A: This sort of calculation seems to be virtually unheard of in real life, though. Very few people actually face trade-offs like showers vs. donations. When they think they do, it seems to almost always be an artificial trade-off they're using as a rationalization for their wasteful behavior. I realize this is a rather uncomfortable claim, since it makes it implies some people in my social circles aren't being very rational or understanding their own psychologies very well. I'm always hesitant to make such claims, but I think this one's rather important, and I hope we can all agree we're very imperfect in our rationality and don't understand much of our own psychologies. I know I fit that mold, and I always try to appreciate when people point out mistakes I might be making. I also think these irrationalities are especially common when it comes to very ingrained social norms like using hot water for showering, so we should be especially wary here.

B: Yes, people don't usually think of things this way, but that's a problem! People with the best intentions who really want to help others and make the world a better place end up doing a whole smattering of things where some are far far more important than others. Donating to effective charities isn't always the way you can make the most positive impact, but it just goes so much farther than avoiding hot showers or so many other things you see people recommending.

A: Not taking hot showers remains relevant to poor people who cannot afford to donate without making substantial hits to their quality of life. There is constant talk of donating first, doing other stuff later, from EA, yet it seems to be forgotten that not everyone is in a position to donate at all.

B: So we're talking about someone poor enough that $5/year would be a significant hardship? In that case I wouldn't push for them to donate, but I also wouldn't push for them to give up hot showers. They're poor enough that they're probably not able to afford thirty minute showers, and what hot water they do use is probably pretty important to them. They're struggling enough to get by, I wouldn't want to make things any harder.

A: Maybe showers themselves aren't that important, but they're part of a whole movement of people voluntarily reducing their consumption to help our society balance its books and become sustainable. We're trying to spread a norm of walking as lightly on the earth as possible. Some of these activities have a larger benefit than others, but norms spread best as a whole package of consistent ideas and our core message is "use only what you need". Hot showers are a luxury that nearly everyone in the world does without; this is really not too much to ask.

B: The problem with that norm is it doesn't distinguish between luxuries that are minimally harmful and ones where the harm is significant. Following that norm you end up with people putting a huge amount of work into things that aren't actually that helpful in pursuit of purity while the most impactful things don't get the focus they need. I'm pushing for a different norm instead: find the places where you can do the most good for the least self sacrifice. Maybe that means donating a kidney to someone who's on dialysis, maybe that means giving money to the AMF to keep people from getting malaria, maybe that means finding work that pays a little less but helps find non-combustible uses for coal so we end up burning less of it. Spend your altruistic energy and willpower where it will make the most difference.

(This post inspired by people making arguments against eating dairy in the comments on this post that would apply equally well against taking hot showers. Several of A's statements are modified comments that were originally about dairy-vs-donations.)