How the upgrade savings calculator works
The payback arithmetic
Annual savings = (old − new) watts × hours × 365 ÷ 1000 × rate. The classic: a 60 W incandescent replaced by a 9 W LED at 3 h/day saves $5.57/year per bulb — a $2 LED pays back in five months and then saves for a decade. The calculator generalizes this to any swap.
The payback rules of thumb
- Payback under 2 years: do it — lighting, old fridges, failed appliances being replaced anyway.
- 2–5 years: do it at natural replacement time — do not discard working appliances for the math alone (embodied energy counts).
- Over 7 years: electricity savings alone rarely justify it — comfort, noise, and features must carry the purchase.
The case list
- Lighting: the highest-return upgrade in history — incandescent-to-LED pays back in months.
- Pre-2000 fridges: the second-highest — old fridges in garages cost $100+/yr more than modern ones.
- Electronics standby: smart plugs ($10) killing 10 W of vampire draw save $13/yr per device — payback in months.
- HVAC: the big numbers, but paybacks run 5–15 years — insulation and sealing usually beat equipment swaps (see InsulPro's payback ladder logic).