Here’s what Daylight Saving Time claims to save and what the evidence actually shows that it may not be:
Energy
The original purpose.
DST was introduced with the idea that shifting an hour of daylight into the evening would reduce lighting and heating costs.
What research shows now:
- Any energy savings from reduced lighting are tiny or nonexistent.
- Modern energy use is dominated by HVAC, appliances, and electronics, which aren’t helped much by shifting the clock.
- Some studies even find slight increases in energy use because people run air conditioning more on warm, bright evenings.
Bottom line:
It barely saves energy.
Safety
Claims: More daylight in the evening reduces traffic accidents.
Evidence:
- Evening crash rates often go down a bit.
- But the switch itself spikes accidents for a few days because people lose sleep and commute while tired.
Bottom line:
A little evening safety gained; morning and transition risks added.
Economic activity
More evening daylight encourages:
- Shopping
- Dining out
- Outdoor recreation
Retailers, restaurants, and tourism sectors love DST.
Bottom line:
DST boosts consumer spending more than it saves energy.
Human health
This is where DST costs rather than saves:
- The spring shift disrupts sleep and circadian rhythms.
- Heart attacks, strokes, and workplace accidents increase on the days after the switch.
- Sleep scientists overwhelmingly oppose the twice-yearly clock changes.
Bottom line:
It costs health, productivity, and sleep.
So what does DST really “save”?
Not energy. Not health.
If anything, it “saves” daylight for after work, making evenings feel longer and more active.
But the tradeoffs — tired commuters, disrupted sleep, and minimal energy benefit — mean many countries are reconsidering it.