Models CEER degradation with age, room sizing, and real annual cooling hours to show whether upgrading pays for itself.
Room & Current Unit
Recommended capacity: ~5,000 BTU
Sizing note: This unit may be oversized, leading to high humidity. Oversized A/C cools quickly but cycles off before removing moisture.
Effective CEER after age: 9.5
New Unit & Usage
Cost Comparison
Current — annual kWh
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New — annual kWh
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Current unit—
New unit—
Summer monthly (÷4 mo)
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Summer monthly (÷4 mo)
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Break-even payback
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Adjust inputs to see payback timeline.
Practical tips & common mistakes
Sizing beats brand
An oversized window unit short-cycles — cool but clammy. Aim for ~20 BTU per sq ft in moderate climates, less in shade.
Blocking airflow
Units need side and rear clearance. Shrubs, curtains, or tight sleeves choke CEER and ice the coil.
Filter and seal
Foam side seals and annual coil cleaning often recover more efficiency than replacing a slightly undersized working unit.
CEER degradation
Age erodes effective CEER through refrigerant leaks and fan wear. Compare degraded baseline vs new label rating, not sticker from 2008.
Note: CEER ratings and sizing rules are estimates. Actual performance depends on installation, climate, shading, and insulation. CEER degrades ~2%/yr modeled here for planning only.