# How is a heat pump sized for a Sacramento home?

> Heat pump sizing in Sacramento: Manual J at local design temperatures, why old tonnage misleads, Title 24 oversizing limits and the City's 25% permit rule.

URL: https://tulesacramentoheatpump.com/guide/heat-pump-sizing/

Learn

How a load calculation turns your house, your town's design temperatures and your ducts into a capacity, why the old condenser's tonnage is a poor guide, and what Title 24 and the City permit allow.

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](https://tulesacramentoheatpump.com/) 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.

Key takeaways

- Sizing starts with heat gain and heat loss for each room, calculated at local design conditions
- Sacramento airport's 1% cooling design is 98°F and its 0.2% heating design is 31°F (CEC JA2)
- In this climate the cooling load usually sets the size; heating capacity is then checked at the winter design point
- Title 24 limits how far a replacement heat pump may exceed the calculated load unless airflow is verified at 350 cfm per ton
- The City of Sacramento's standard change-out permit allows no more than 25% above the old unit's size

## 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](https://tulesacramentoheatpump.com/dual-fuel-heat-pump/), the furnace carries the rest; the [aux heat and defrost guide](https://tulesacramentoheatpump.com/guide/heat-pump-aux-heat-defrost/) 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](https://tulesacramentoheatpump.com/guide/heat-pump-permit-title-24/) covers the alternatives.

Get a heat pump sized to your house

Room measurements, insulation and duct checks go into the load calculation before any equipment is named.

## 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](https://tulesacramentoheatpump.com/variable-speed-heat-pump/) 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](https://tulesacramentoheatpump.com/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](https://tulesacramentoheatpump.com/guide/how-to-compare-heat-pump-quotes/) shows how to check sizing across bids, and the [hot weather guide](https://tulesacramentoheatpump.com/guide/heat-pump-hot-weather/) covers summer performance.

The [home readiness check](https://tulesacramentoheatpump.com/tools/heat-pump-assessment/) is a quick first look at duct and panel issues. When an older heat pump is being replaced, [heat pump replacement](https://tulesacramentoheatpump.com/heat-pump-replacement/) is the place to start. For a sized proposal on your own house, call (916) 516-1454 or [request an estimate](https://tulesacramentoheatpump.com/contact/).

## Questions about this guide

### Is a bigger heat pump safer for 105-degree afternoons?

No. A system sized above the load satisfies the thermostat quickly, shuts off and restarts, which wastes energy, adds wear and leaves rooms at the end of the ducts uneven. Title 24 caps the margin on a replacement heat pump unless airflow is verified at 350 cfm per ton or more. Sizing to the 1% design temperature and accepting a small drift on record days is the better trade.

### How do you size a heat pump from a gas furnace's Btu rating?

You don't, at least not directly. A furnace's Btu number is its fuel input, often far above the house's heating load, and in Sacramento the cooling load usually sets the heat pump's size anyway. The furnace rating says what someone installed, not what the house needs. A room-by-room load calculation at local design temperatures is the reliable route.

### What does a load calculation need from the homeowner?

Mostly access and history. The person running it measures rooms, windows and ceiling heights, notes insulation and duct locations, and checks which way the house faces. It helps to know about added insulation, replaced windows, additions or a converted garage, and which rooms run hot or cold now, because those details change the load and the airflow each room should get.

Want this answered for your house?

Call with your current system, the rooms that bother you and your ZIP code.

## Related service

Heat pump replacement

An aging heat pump swapped for a matched, correctly sized system, with the ducts tested and the charge verified under Title 24.

## More guides

- Learn [How does a heat pump hold up in Sacramento's hot weather?](https://tulesacramentoheatpump.com/guide/heat-pump-hot-weather/)What happens inside a heat pump on a 100-degree afternoon, how the design temperature for your town sets its size, why attic ducts and outdoor-unit placement matter, and how to run it around summer peak pricing.
- Learn [What is heat pump aux heat, and when should it run in Sacramento?](https://tulesacramentoheatpump.com/guide/heat-pump-aux-heat-defrost/)How backup heat strips, defrost cycles and thermostat controls work together, why the valley floor rarely needs strips for capacity, what they cost to run on each utility's rates, and when a furnace makes the better backup.
- Learn [What do SEER2 and HSPF2 ratings mean for a Sacramento heat pump?](https://tulesacramentoheatpump.com/guide/seer2-hspf2-ratings/)How the cooling and heating efficiency ratings are built, how to turn HSPF2 into a COP you can compare with your utility's break-even figure, and why installation quality decides whether a system reaches its rating.
- Learn [What does a heat pump permit in Sacramento involve, and what does Title 24 check?](https://tulesacramentoheatpump.com/guide/heat-pump-permit-title-24/)The permit office for each part of the region, what the City of Sacramento's standard change-out permit allows, every Title 24 test a change-out carries, and how SB 222 reshapes permits from 2027.
- Learn [How do you compare heat pump quotes in Sacramento?](https://tulesacramentoheatpump.com/guide/how-to-compare-heat-pump-quotes/)A line-by-line checklist for putting bids side by side, the questions that expose a missing scope, what the SMUD rebate wording should say, and how to use SMUD's published median as a sanity check.