"It saves money" is the renewable energy message that works on everyone. And it lasts.

Almost everything we know about persuasive messages comes from measuring people seconds after they read one. That tells you about the immediate reaction. It tells you nothing about whether the message is still in their head a week later, which is what matters for a campaign. This study, led by Abel Gustafson in his academic role at the University of Cincinnati with collaborators at the Yale Program on Climate Change Communication and Georgetown University, tested three messages about renewable energy and then followed the same people for three weeks to watch the effects fade.

The research team recruited 2,891 self-identified Republicans and Democrats and showed each a short, infographic-style message that emphasized one benefit of renewable energy: it costs less than fossil fuels, it grows the economy and creates jobs, or it reduces global warming. A control group read about an unrelated topic. The team measured beliefs about renewables and support for renewable energy policy right away, again after about 11 days, and once more after another 13 days.

Right away, the cost-savings message had the largest effect on beliefs, and the effect was nearly the same size for Democrats (d = 0.76) and Republicans (d = 0.68). The economy and jobs message came next. The global warming message was the weakest, and much weaker for Republicans (0.17) than for Democrats (0.43). On the index of policy support, the cost-savings and economy messages had small positive effects in both parties. The global warming message did not move Republicans' support at all.

Every effect dropped sharply over the first ten days and then flattened out, a pattern that has since shown up in study after study. But the plateaus sat at different heights. After three weeks, Democrats still held 44% of the cost-savings effect and Republicans 57%. The economy message held up well for Republicans (66%) but mostly faded for Democrats (15%). The global warming message retained 36% among Democrats and essentially nothing among Republicans. Cost savings was the only message that was both large and durable for both parties.

For communicators, the result is unusually clean. A message about lower costs is not a compromise frame that works a little for everyone. It was the best-performing message for both parties and the most durable one. Given how quickly the cost of renewables has fallen, it also has the advantage of being true, which makes it a strategy that gets stronger over time.