Estimate room heating or cooling capacity in BTU/hour and kW with explicit dimensions, insulation, temperature and optional internal-gain assumptions.
01 / ROOM & ASSUMPTIONS
A simplified capacity planning model, not a professional HVAC load calculation. Insulation presets and additional adjustments are illustrative assumptions.
02 / PLANNING ESTIMATE
Enter the room dimensions and review assumptions before calculating.
03 / MODEL & LIMITATIONS
BTU/hour is a rate of heat transfer: the heat a heater supplies or an air conditioner removes each hour. It is not energy consumed or an electricity bill; electrical input also depends on equipment efficiency.
Better insulation and lower air leakage reduce heat transfer. Sunlight warms the room, while people and appliances add heat indoors. Climate affects the outdoor design temperature; humidity also adds latent cooling load, which this simple model does not calculate.
Cooling starts with the ENERGY STAR room-area table at an 8 ft ceiling. Heavy shade reduces the base by 10%; very sunny exposure adds 10%; each occupant above two adds 600 BTU/hour. Height, temperature-difference and insulation scaling plus the optional solar/appliance assumptions are this tool’s illustrative extensions, not an ENERGY STAR certified calculation.
Heating watts = envelope U × exposed area × ΔT + window U × glazing × ΔT + 0.33 × air changes/hour × volume × ΔT. Glazing replaces an equal opaque wall area; no double counting. Illustrative presets: good U 0.4 / ACH 0.5; typical U 0.8 / ACH 0.8; poor U 1.6 / ACH 1.5. Cooling insulation multipliers: 0.9 / 1 / 1.15. Values are assumptions, not building-code specifications.
IT BTU = 1055.05585262 J; therefore 1 W = 3600/1055.05585262 BTU/hour. One cooling ton = 12,000 BTU/hour. kW is thermal capacity, not equipment power input; efficiency is not modeled.
Construction, humidity, ventilation, shared walls, solar geometry and local design conditions can materially change actual load. This does not replace a professional HVAC calculation or guarantee that a specific appliance will perform adequately.
ENERGY STAR room-AC sizing table and adjustment guidanceEnter your values locally; no inputs are uploaded.
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Choose heating or cooling, enter room dimensions and assumptions, then calculate. Advanced settings cover design temperatures, windows and appliances. Review the planning range and model limitations.
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The ENERGY STAR room-AC area table is the baseline for 100–2,500 ft² at an 8 ft ceiling. This planning model applies disclosed height, insulation, temperature and sun adjustments, then adds 600 BTU/hour per occupant above two, appliance heat and optional extra solar glazing gains. Adjustments beyond the source table are illustrative assumptions, not an ENERGY STAR certified load calculation.
Heating uses envelope transmission U × area × temperature difference plus 0.33 × air changes/hour × room volume × temperature difference. All six room surfaces are assumed exposed; windows replace part of the wall area. Preset U-values and air-change rates are illustrative, not measurements of your building.
Room dimensions use meters or decimal feet. Window area uses corresponding square units. Design temperatures may be Celsius or Fahrenheit. Output uses IT BTU/hour and kW; cooling also shows tons at 12,000 BTU/hour per ton.
For cooling, enter only extra sun-exposed glazing beyond typical baseline conditions; modeled solar gain is adjustable, and appliance watts are treated as room heat. Heating uses total glazing and an assumed window U-value, without subtracting occupant/appliance/solar gains.
It is an illustrative plus/minus 20% planning sensitivity band, not a statistical confidence interval or a recommendation to oversize equipment. Actual capacity and humidity control depend on equipment and building details.
No. Complex exposure, adjacent spaces, humidity/latent loads, ventilation, construction and local design conditions require a professional calculation. The result is a simplified planning estimate, not an equipment guarantee or installation recommendation.