Free HVAC load estimate

See how your home moves heat.

Estimate your home’s heating and cooling load, see what drives it, then compare several ways to heat and cool the same home.

Start my estimateSee how it works

A planning estimate to help you understand HVAC sizing. It is not a full ACCA Manual J report or a final equipment recommendation.

HomeLoadSystem designEquipment
Where a home gains and loses heatHouse cutaway showing heat moving through the roof, walls, windows, and floor, plus outdoor air leaks, sunlight, people, and appliances. ROOF + ATTICheat through the roofWINDOWSsunlight + heat flowOUTDOOR AIRdrafts + air leaksHEAT FROM INSIDEpeople + appliances HEAT FLOWAIR LEAKAGE
THE BUILDING IS THE FIRST SYSTEM.
Your home’s size, insulation, windows, and air leakage determine how much heating and cooling it needs.

01 · Tell us about your home

Tell us about your home.

We’ll ask four short sets of questions about your weather, space, insulation, windows, and household. You’ll see every assumption before we calculate the load.

What’s the weather like where you live?

Choose the climate that best matches your area. A full Manual J uses local design temperatures; this estimate uses the broad ranges explained below.

We use this choice to estimate the temperature difference your system must handle.

03 · How the estimate works

What this estimate includes—and what a full Manual J adds.

This HVAC load calculation estimates heat moving through the walls, roof, floors, and windows; outdoor air leaking in; sunlight through the glass; and heat from people and appliances. It is a planning estimate, not ACCA-approved software or a full ACCA Manual J report.

heat loss = Σ(U × area × ΔT) + infiltration
cooling load = conduction + infiltration + solar + internal gains

A professional Manual J goes further with room-by-room measurements, local design weather, detailed construction, duct losses, ventilation, humidity, and verified equipment performance.

WeatherFive broad climate choices. A full Manual J uses local design temperatures.
Walls, roof + floorsWe estimate their area and insulation from the home details you provide.
Windows + sunWindow type, U-factor, solar heat-gain coefficient (SHGC), direction, and shade.
Air leakageWe estimate drafts and natural air changes. A blower-door test is more accurate.
HumidityThis estimate does not separately calculate the latent, or moisture, portion of the cooling load.
EquipmentWe do not choose a nominal size automatically. Published capacity at the design temperature must be checked first.

Learn as you go

Know what the load means before choosing equipment.

Straight answers

Common HVAC load calculation questions.

Is this a full ACCA Manual J calculation?

No. This is a planning estimate based on simplified home measurements and broad climate choices. A full Manual J uses detailed room-by-room information and local design weather.

Is calculated load the same as nominal HVAC size?

No. The load is the amount of heating or cooling your home needs. Before recommending equipment, we also check published capacity at design conditions, humidity control, modulation, airflow, and whether the components are approved to work together.

Why are heating and cooling loads different?

Heating load is mostly heat leaving through the home and cold outdoor air leaking in. Cooling load also includes sunlight, people, appliances, and warm outdoor air leaking in.

Can I compare system types without recalculating?

Yes. Your home and calculated load stay the same while you compare different ways to heat and cool it.