A heat pump for a Sacramento home is sized from a room-by-room load calculation, usually ACCA Manual J, run at your own town’s design temperatures. On the valley floor the summer afternoon sets the capacity, and that capacity usually covers the winter heating load as well. The old condenser’s tonnage is a starting clue, not an answer.
Tule Sacramento Heat Pump sizes and installs ducted heat pumps across the Sacramento region, with the installations carried out by licensed and insured contractors. Every system proposed through the site starts from a load calculation, not from a nameplate.
What a load calculation measures
A load calculation adds up how fast the house gains heat in summer and loses it in winter, room by room, at a defined outdoor condition.
Heat gain (summer)
Sun through windows, especially west-facing glass; heat conducted through walls and the ceiling from a hot attic; outdoor air leaking in; people, lights and appliances; and heat picked up by ducts that run through the attic.
Heat loss (winter)
Heat conducted out through walls, windows, floors and ceilings; air leaking out around doors, recessed lights and attic hatches; and losses from ducts in unconditioned space.
| What gets measured | Why it changes the size |
|---|---|
| Room dimensions and ceiling height | Sets the volume and surface area of each room |
| Window area, glass type and orientation | West glass can dominate a summer load |
| Wall and attic insulation | A better envelope shrinks both loads |
| Air leakage | Leaky houses gain and lose more heat |
| Duct location and condition | Attic ducts add load; leaky ducts add more |
| Local design temperatures | Sets how hard the system must work on design days |
The result for each room also tells the duct designer how much air that room needs, which is why a room-by-room calculation matters more than a whole-house rule of thumb.
Sacramento’s design temperatures
The California Energy Commission’s Reference Appendices (JA2) list the design conditions for each station. They differ more across the region than most people expect.
| Station | 1% cooling design | 0.2% heating design |
|---|---|---|
| Sacramento airport | 98°F | 31°F |
| Elk Grove | 98°F | 34°F |
| Carmichael | 98°F | 35°F |
| Citrus Heights | 98°F | 26°F |
| Roseville | 100°F | 30°F |
| Rocklin | 103°F | 26°F |
| Davis | 97°F | 30°F |
| Placerville | 97°F | 26°F |
Why cooling usually decides
The gap between 98°F and 31°F is the key. A Sacramento house typically needs more capacity to hold 75°F against a 98°F afternoon than to hold 68°F against a 31°F morning, so the system is chosen for cooling and its heating output is checked at the winter design point.
Rocklin and Loomis are different: their design afternoons run 102°F to 103°F and their 0.2% heating design is 26°F to 27°F, so a heat pump sized there needs more cooling capacity and has to keep more of its output at low temperatures.
The heating check
Heat pump output falls as outdoor temperature drops. The selection compares the manufacturer’s capacity at your heating design temperature with the calculated heat loss. Where the two meet is the balance point. Below it, backup heat or, in a dual fuel system, the furnace carries the rest; the aux heat and defrost guide explains how that is controlled.
Why the old tonnage misleads
One ton of cooling is 12,000 Btu per hour. The tonnage on the old condenser tells you what was installed, not what the house needs.
Where the old number came from
The original system may have been sized with a generous margin, by square footage or by matching an even older unit. Since then the house may have gained attic insulation, dual-pane windows or an addition. Homeowners report bids sized by counting registers or by copying the old label with no room measurements at all.
The furnace number is worse
A gas furnace’s Btu rating is fuel input. Output is lower, and many furnaces were oversized for heating in a climate where heating loads are modest. Copying it into a heat pump selection usually inflates the size.
The cost of oversizing
A system that is too large cools the air near the thermostat quickly and shuts off. Short cycles mean more starts, which add wear; lower efficiency, because each start wastes energy before the system settles; and uneven rooms, because the far ends of the ducts never get enough run time.
What Title 24 allows
The CEC’s alteration rules limit oversizing for replacement heat pumps when airflow is not verified at 350 cfm per ton or more. In a cooling-dominated climate like Sacramento’s, cooling capacity may exceed the calculated cooling load by no more than about 6,000 Btu per hour, and heating capacity may exceed the heating load by no more than about 12,000.
What the City permit assumes
The City of Sacramento’s standard web permit for a change-out keeps the new unit in the same place and within 25% of the old unit’s size. Of the 1,950 heat pump permits the City issued from October 26, 2025 to October 25, 2026, 1,682 carried that condition. A load calculation that calls for a bigger jump moves the job off the simple permit path. The permit and Title 24 guide covers the alternatives.
Undersizing is a real risk too
A system that is too small runs constantly on design days and lets the house drift well above the setting. In winter it leans on backup heat more often, which raises bills. A careful selection lands close to the calculated load, often with a variable-speed or two-stage compressor that can run below full output most of the year. The variable-speed heat pump page explains why that flexibility makes sizing more forgiving.
Ducts have to match the capacity
Capacity only arrives if the ducts carry it. Title 24’s refrigerant charge check assumes at least 300 cfm of airflow per ton, and the room-by-room loads say where that air should go. A three-ton system on ducts that can move only enough air for two tons will not perform like three tons. Manual D is the duct design method that follows the load calculation; heat pump ductwork covers what happens when the existing ducts fall short.
How sizing shows up in a quote
A complete proposal names the load calculation result, the selected outdoor unit and matched indoor coil or air handler, and the capacity at your design temperatures. SB 222 points the same way: once cities and counties offer automated online permitting for licensed contractors, due by July 1, 2028, the contractor certifies a load calculation as part of the permit. The quote comparison guide shows how to check sizing across bids, and the hot weather guide covers summer performance.
The home readiness check is a quick first look at duct and panel issues. When an older heat pump is being replaced, heat pump replacement is the place to start. For a sized proposal on your own house, call (916) 516-1454 or request an estimate.
