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Heating · Sizing
How big a furnace do you actually need?
Rough sizing in 30 seconds. Adjusts for climate zone, insulation quality, ceiling height, and window count — the four inputs that actually move the number.
This is an engineering estimate, not a Manual J load calculation. For a permit-grade calc — required for a warranty install — book a home assessment and we'll deliver a signed report.
Recommended output
140,000 BTU/hr
Estimated design-day load: 119,000–144,000 BTU/hr at -15°F outdoor design temperature.
- • Single-stage 92% AFUE units run at their nameplate rating.
- • Modulating 96–98% AFUE units can be sized slightly larger for recovery without short-cycling.
- • Cold-climate heat pumps at this load: 3–4 ton inverter-driven with a 40–60k BTU backup coil.