Defaults, prices, and peer comparisons in environmental behavior.

Social comparison reports — showing households their energy use relative to neighbors — produce persistent 2% energy reductions at very low cost.

Opower's randomized experiments across 85+ utilities found that home energy reports showing households their consumption relative to efficient neighbors produced average reductions of 2.0–2.5% in energy use. Effects persisted for years after initial contact and survived changes in season, home ownership, and utility pricing. A 2014 analysis of 8 million households found the intervention was more cost-effective than most utility efficiency programs. The mechanism is normative comparison — people adjust consumption toward what they perceive as the norm.

Switching electricity defaults to green energy dramatically increases adoption without reducing customer satisfaction.

Germany's green electricity default experiment found that switching the default from conventional to renewable electricity for new residential customers increased green energy adoption from approximately 7% (opt-in) to 69% (opt-out). Customer satisfaction and retention were unaffected. The default effect — the tendency to stay with whatever option is presented as the status quo — operates powerfully even for decisions with real cost implications.

Carbon taxes produce measurable emissions reductions without the economic harm opponents predict — but political durability requires revenue recycling.

British Columbia's carbon tax — introduced in 2008 at C$10/tonne and rising to C$50/tonne — produced a 15% reduction in fuel consumption relative to the rest of Canada, with no measurable GDP effect. The tax was revenue-neutral, with proceeds returned as tax cuts and rebates. Seattle's minimum wage study and London's congestion charge provide parallel evidence that price signals produce behavioral change without the employment and congestion effects critics predicted.

Solar Panel Adoption Peer Effects

Connecticut, United States · 2014

Peer effects in solar adoption — the phenomenon where one household adopting solar increases the probability that nearby households adopt — are real but modest. Simply showing people that their neighbors have solar does not reliably increase adoption; the barrier for most households is financial, not informational.