Free Mini-Split Calculator for Bay Area Homes
What size ductless heat pump does your room, ADU, or garage conversion actually need? Get an instant capacity estimate using California climate zone data, your home's vintage, and ASHRAE residential standards. Built by licensed Bay Area contractors who install these systems for a living.
Use this tool to estimate room capacity, then review equipment options, electrical work and permit requirements with your installer.
Where is the property
Tell us about the room
Sizing one room? For an ADU, use a single "Studio / ADU" preset. For multiple rooms (whole-house multi-zone), we'll handle that during a free consultation because it requires per-room measurement.
Your 200 sqft bedroom in San Ramon (CZ 12) needs roughly a 6k BTU/h head to handle both cooling on hot days and heating during winter cold snaps. This is the closest standard mini-split size. Heads come in 6k, 9k, 12k, 15k, 18k, 24k, 30k, and 36k.
Note: 6k is the smallest standard head. For very small spaces, oversized heads short-cycle and dehumidify poorly. A technician may recommend a different solution like a PTAC or window unit.
Why a "$700 Amazon mini-split" isn't the same thing as a properly installed system
We say this carefully: a DIY-installable Mr. Cool or Pioneer mini-split kit from Amazon can work for some scenarios. But the failure rate is higher than people realize, and the failure modes are expensive. Here's what actually goes wrong, in our experience:
Refrigerant problems
Pre-charged line sets are sized for a specific length. If your run is shorter, you have over-pressure. Longer runs need added charge, which requires EPA Section 608 certification and gauges. Most DIY installs end up with low or improper charge, which kills compressor life by 30-50%.
Line set length wrong
DIY kits come with 16 or 25 ft line sets. Reality: pre-charged DIY kits cannot be field-modified because the flares are factory-sealed. If your install needs 18 ft, you have 7 ft of slack to coil up in the wall, which causes vibration noise and oil-return problems.
Electrical done wrong
A 24k mini-split pulls 15-20 amps at 230V. That needs a dedicated 230V/30A circuit, disconnect at the outdoor unit, GFCI protection in some jurisdictions, and proper bonding. Tapping an existing 115V circuit or skipping the disconnect creates code violations and fire risks.
No permits, failed inspections
California requires a building permit for any HVAC installation. No permit means no Title 24 compliance, no inspection, no record for resale, and potential insurance issues if a fire traces back to the install. Selling the home later requires painful retroactive permits.
Warranty terms
As a Mitsubishi Electric Diamond Contractor, we register your M-Series or P-Series system for the Mitsubishi Electric 12-year parts and 12-year compressor limited warranty. We register all indoor and outdoor units within 90 days of installation. This coverage applies to a single-family home while the original owner continues to live there and is not transferable. Our standard workmanship warranty is 2 years.
Condensate management
Mini-splits produce 1-3 gallons of condensate per day during cooling. DIY kits include a basic drain line, but proper installation requires correct slope, a trap, overflow protection in attic installs, and sometimes a condensate pump. Ceiling stains, water damage, and mold are common DIY consequences.
We're not anti-DIY in general. We're pointing out that the price gap between the Amazon kit and a proper install covers real labor, certifications, equipment, and warranty protection, not merely contractor margin. The decision between them is yours; we just want it to be an informed one.
Same capacity, very different installs
"12,000 BTU mini-split" can mean a $400 wall unit you see in every Asian hotel, or a $2,500 flush ceiling cassette that's nearly invisible. Picking the right head type is more about your room geometry and aesthetic than capacity. Here's the breakdown.
Wall-mounted
Most common type. Mounted high on an interior wall, blows down and out.
One-way ceiling cassette
Recessed into ceiling, blows in a single linear direction. Compact.
Four-way ceiling cassette
Square ceiling-recessed unit, 360° air distribution from center.
Floor-mounted
Sits at floor level like a radiator. Blows up and out.
Concealed ducted mini
Small air handler hidden in attic/ceiling, with short duct runs to ceiling registers.
What's actually in a mini-split install
People ask "why does this cost so much more than the equipment?" The equipment is maybe 40% of the total. Here's where the rest goes and why this isn't a job you can shop on price alone.
Outdoor + indoor units
- ·Inverter-driven outdoor unit (heat pump or AC-only)
- ·Head(s) matched to your room sizes
- ·New ductless installations: Mitsubishi Electric
- ·Equipment selected for the room load, layout and design temperature
Line sets & commissioning
- ·Copper line set sized to your specific run length
- ·Vacuum-pulled to 500 microns before charging (most DIY installs skip this)
- ·Pressure-tested with nitrogen for leak detection
- ·Refrigerant charge adjusted for your line set length per manufacturer specs
Power infrastructure
- ·Dedicated 208-230V circuit (most installs)
- ·Disconnect switch at outdoor unit (code required)
- ·Possible sub-panel for ADU/garage detached structures
- ·Possible main panel upgrade if home has 100A service ($2,500-5,000)
Title 24 & building permit
- ·Mechanical permit from your city
- ·Title 24 compliance documentation for the install
- ·Inspection by city official upon completion
- ·For ADUs: separate plan check and ADU-specific permit fees
Condensate & mounting
- ·Condensate drain with proper slope and overflow protection
- ·Condensate pump (if gravity drain isn't possible)
- ·Outdoor unit pad or wall bracket, vibration isolators
- ·Line set cover (paintable plastic raceway) for clean exterior look
Warranty & commissioning
- ·Manufacturer warranty validated (only with certified installer)
- ·Workmanship guarantee from contractor
- ·System commissioning report (refrigerant, electrical, controls)
- ·Future service relationship, with the same techs who know your install
ADUs & garage conversions: special considerations
California's ADU and SB 9 reforms have created a boom in detached structures. Mini-splits are the natural HVAC choice for them: no ducts, no gas line, and no shared system with the main house. But there are Bay Area-specific gotchas:
2029 furnace emission standard
Air District Rule 9-4 sets a zero-NOx standard for covered furnaces manufactured after January 1, 2029. It does not require replacing a working furnace. Check the equipment scope, current rule updates and local permit requirements for your ADU. Air District rule information.
Sub-panel almost certainly needed
ADUs typically need their own electrical sub-panel (60-100A). The mini-split is one circuit on it, but the sub-panel itself plus a feeder run from the main house can be $3,000-$6,000 depending on distance and trenching needs. Some homes need the main panel upgraded first (100A → 200A) to free up capacity.
120V plug-in heat pumps now exist
If your main panel can't support a sub-panel upgrade easily, 120V plug-in heat pumps (Gradient, Friedrich) plug into a standard outlet. They have lower capacity (8-12k BTU) and slightly lower efficiency, but they bypass the panel-upgrade cost entirely. Great for studio ADUs and garage conversions in old homes.
Insulation is the #1 sizing factor
Original garages are typically uninsulated. A converted garage with R-13 walls / R-30 ceiling sizes very differently from one with R-4 / R-11. We measure existing insulation during consultation, and that often shifts head capacity by one full size (e.g. 12k → 18k for a 400 sqft space).
One head or two?
500-700 sqft ADU with bedroom + living area: do you put one 18k head central, or two 9k heads (one per room)? Sound transmission, sleeping comfort, and per-zone control matter. We'll walk this trade-off during the consult with your floor plan.
ADU plans + HVAC = different plan check
ADU mechanical plans go through a different plan check than a standard residential remodel in most Bay Area cities. We've filed in San Ramon, Pleasanton, Walnut Creek, Oakland, Berkeley, San Francisco. Plan check time varies wildly, from 2 weeks in Pleasanton to 10+ weeks in Berkeley.
Air District rules for new equipment
Checked September 28, 2026. These dates come from the rules adopted in March 2023 and refer to equipment manufacture dates. They apply within the Air District's jurisdiction to the equipment defined by each rule. Working equipment does not have to be removed. Check current amendments before selecting a replacement.
Covered small tank water heaters
Rule 9-6 sets the adopted zero-NOx standard for covered storage water heaters with heat input of 75,000 BTU/h or less manufactured after this date. Mobile-home units are exempt. Proposed 2026 amendments remain under consideration.
Covered furnaces
Rule 9-4 sets the adopted zero-NOx standard for covered furnaces manufactured after this date. The furnace heat-input limit is below 175,000 BTU/h; mobile-home furnaces are excluded. The separate 65,000 BTU/h limit concerns cooling capacity in combination units.
Covered larger water heaters and boilers
Rule 9-6 sets the adopted zero-NOx standard for covered water heaters and boilers with heat input from 75,001 to 2,000,000 BTU/h manufactured after this date. Check the rule definitions and exemptions for the equipment being considered.
For your project: confirm the appliance type, nameplate rating, manufacture date and current rules with your installer. A heat pump is one option; electrical capacity, sizing and permit requirements still need to be checked. Read the Air District updates before choosing equipment.
Where the rebates actually stand in October 2026
We'll be straight with you: most of the big rebates you read about online are closed or reserved as of October 2026. We'd rather tell you upfront than promise savings that don't exist. There are still some local programs active, depending on where you live in the Bay Area.
Expired December 31, 2025. Up to $2,000 for qualifying heat pumps. No replacement program currently scheduled.
Single-family funding was fully reserved February 24, 2026; multifamily funding followed September 1, 2026. Neither accepts new reservations.
Heat pump HVAC rebates $1,000-$3,100. Fully reserved November 14, 2025. The program may relaunch with future funding but timeline unannounced.
Home+ ended October 18, 2024. Other BayREN programs have separate eligibility rules; Home+ incentives are no longer available.
For eligible SVCE accounts, including Cupertino: gas-to-heat-pump HVAC rebates are $2,000 standard or $3,000 income-qualified; electric-resistance replacements receive $500 or $1,500. Reserve before installation. San Jose uses SJCE; Santa Clara uses Silicon Valley Power.
$1,500 base rebate for replacing a gas heater or furnace with a qualifying heat pump HVAC system. CARE or FERA may add $1,000, and a limited Menlo Park grant may add $1,500. Check account, equipment and application eligibility.
Piedmont, Palo Alto, Healdsburg, Santa Clara, and Alameda Municipal Power customers have various local heat pump and panel upgrade rebates. We check current programs for your address during consultation.
No-charge energy-saving upgrades and repairs for qualifying households. PG&E does not publish a fixed HVAC or water-heater dollar amount; the approved scope is determined after an assessment. HVAC replacement has additional homeowner and existing-equipment restrictions.
Programs change quarterly. The federal and state programs may relaunch with new funding in late 2026 or 2027. We track rebate availability for every consultation and handle the paperwork if you qualify. If you're considering a heat pump primarily for rebates, the math is harder in October 2026 than it was in 2024. If you're considering it for comfort, electrification, or BAAQMD compliance, the math still works.
The estimate above is a starting point
The real number depends on your specific room geometry, existing electrical capacity, line set routing, and which rebates apply to your address. We do free on-site assessments across the Bay Area, no obligation, no pressure.
Tri-Valley · Diablo Valley · East Bay · South Bay · San Francisco Peninsula
Licensed contractor (CSLB #1136642) · EPA Section 608 Universal · BBB A+ rating · Serving the Bay Area since 2021
When ductless mini-split is the right answer
Mini-split (ductless) heat pumps are the right call in four specific scenarios across the Bay Area. First: homes with no usable ductwork: common in older Berkeley flats, original Oakland bungalows, and ADUs. Tearing into plaster walls to run new duct trunks costs more than the heat-pump equipment itself. A mini-split skips that entirely.
Second: partial conditioning. You want a master suite cool at night but don’t need (and don’t want to pay to cool) the whole house. A 9,000 or 12,000 BTU/h head solves the problem at a fraction of the cost and operating expense of a central system.
Third: ADU and garage conversions. New livable square footage that the existing central system can’t reach, and shouldn’t reach, because most central systems sized for the original house don’t have the capacity for added space. A standalone 1-ton ductless system is the standard answer.
Fourth: zone-specific load profiles. South-facing rooms with floor-to-ceiling windows have wildly different summer cooling needs than the rest of the house. A central system has to size for the worst room, oversizing every other zone. Mini-splits per zone solve this elegantly. See our ductless mini-split service for install details.
Considering a central ducted heat pump instead?
If your home already has ductwork in decent shape and you want a single hidden system covering the whole house, a central heat pump is usually simpler and cheaper per ton than a multi-head mini-split. Try our free central HVAC load calculator instead, sizes whole-home with Manual J inputs, ducts and returns included.
Mini-split vs central heat pump: which to pick
| Factor | Mini-split (ductless) | Central ducted heat pump |
|---|---|---|
| Existing ducts | Not required | Required (or major retrofit cost) |
| Whole-home coverage | 3-5 heads typical, visible indoor units | One indoor system, hidden in attic/closet |
| Zone control | Per-head (granular) | Per-zone with motorized dampers (extra cost) |
| Cost, single zone | $4,500-$7,500 per zone | Not practical (would still be whole-house cost) |
| Cost, whole home | $15,000-$25,000 for 3-5 head system | $13,000-$17,000 for ducted system |
| Aesthetics | Wall/ceiling heads visible in each room | Registers only (invisible system) |
| Best for | ADUs, additions, no-duct homes, master-only | Whole-home replacements with existing ducts |
Going with central instead? Try the free central HVAC load calculator for ducted-system sizing. New to load math? Read how HVAC load estimation actually works.
ADU and garage conversion HVAC
California’s ADU streamlining laws have made backyard ADUs and garage conversions one of the most common HVAC scenarios in the Bay Area in 2024-2026. The default answer for new conditioned space is almost always a 12,000 or 18,000 BTU/h ductless mini-split. Why:
- Compact outdoor unit: a 1-ton outdoor condenser is roughly 30″ wide × 23″ deep, fits in a side yard easily.
- Single penetration: one 3″ hole through the wall for refrigerant lines, drain, and low-voltage. Minimal structural impact.
- Independent system: your ADU tenant’s thermostat doesn’t affect your main house, and vice versa.
- ADU permit requirements: the equipment and installation must meet the applicable energy code. A heat pump alone does not establish compliance; confirm the plans and documentation with your local building department.
- Rebate-eligible: MCE rebates apply to ADU installs in eligible cities; manufacturer rebates may apply if equipment qualifies.
For garage conversions specifically, mini-split is essentially the only practical answer, running central ductwork into a former garage usually means visible bulkheads or sacrificing closet space. The mini-split head mounts high on the interior wall and stays out of the way.
120-volt plug-in heat pumps, the new category
A growing class of mini-split-style heat pumps plug into an ordinary 120V household outlet, no electrical permit, no panel upgrade, no licensed installer required for the plug-in operation itself. These have exploded in popularity since 2023 for apartments, ADUs, accessory dwellings, and homes where the existing electrical service is already at capacity.
The trade-off: they’re capacity-limited. A 15-amp 120V circuit caps you at roughly 12,000 BTU/h cooling and 8,000-10,000 BTU/h heating, enough for one well-insulated 400-600 sqft room or a small ADU, not enough for a whole-home system. They’re also less efficient (SEER2 14-16 typically) than hardwired 240V models (SEER2 19-26 on premium equipment).
| Model | Type | Capacity | Price range |
|---|---|---|---|
| Gradient All-Weather | Window saddle (no drilling) | 10,000 BTU/h cool, 9,000 heat | $1,800-$2,400 |
| Midea U-Shaped | Window saddle | 8,000-12,000 BTU/h cool | $450-$700 (cooling only, most variants) |
| Windmill AC + Heat | Window saddle | 10,000 BTU/h cool, 9,000 heat | $700-$1,000 |
| Friedrich PHE | Through-wall (sleeve required) | 12,000-14,000 BTU/h heat pump | $1,300-$1,700 |
| LG Dual Inverter Window Heat Pump | Standard window unit | 8,000-12,000 BTU/h heat pump | $600-$900 |
When 120V plug-in is the right call: rental properties (no permit, no landlord-modification issues), accessory dwelling units under 600 sqft, single bedrooms or home offices that need quick conditioning, and homes with electrical panels already at capacity where adding a 240V/30A circuit for a hardwired mini-split would trigger a panel upgrade.
When 120V plug-in is NOT enough: whole-home conditioning (capacity won’t reach), heating in CZ12 inland winters (the cheaper models lose meaningful capacity below 30°F: check the model’s low-temp curve), or anywhere needing more than 12,000 BTU/h cooling capacity.
We’ll talk through 120V vs hardwired during the estimate visit if your situation is on the borderline, sometimes the right answer is one 120V unit in the room that matters most rather than a $15K hardwired system you don’t actually need.
Brand comparison: which mini-split actually wins
This comparison describes equipment you may already own or be researching. We repair and service other mini-split brands; our new ductless installations use Mitsubishi Electric.
| Brand | Cold-climate rating | Warranty | Best for |
|---|---|---|---|
| Mitsubishi Hyper-Heat (M-Series) | Full capacity to 5°F, partial to -13°F | 12-year parts and compressor limited warranty for M-/P-Series; registration and ownership conditions apply | Premium installs; whole-home multi-zone; clients prioritizing longevity |
| Daikin Aurora / Atmosphera | Full capacity to 5°F, partial to -15°F | 12yr compressor / 12yr parts (registered) | Existing single-zone systems; Andrew is factory-trained on Daikin |
| Fujitsu Halcyon LX | Full capacity to 5°F | 10yr parts (registered) | Mid-premium; quieter indoor units; concealed-duct options popular |
| Bosch IDS / Climate 5000 | Full capacity to -4°F (IDS Premium) | 10yr parts / 6yr compressor | Mid-tier; good cold-climate spec; thinner installer network in Bay Area |
| Cooper & Hunter PEAQ | Full capacity to 5°F | 10yr parts / 7yr compressor (registered) | Value-premium hybrid; best price-to-performance in the cold-climate category |
| Pioneer / Senville | Effective to ~14°F | 5-7yr parts / 5yr compressor | Value tier; DIY-friendly pre-charged kits; OK for mild CZ3 only |
| MRCOOL DIY | Effective to 5°F (newer models) | 7yr parts / 5yr compressor | Existing DIY systems: diagnosis and repair; check the model warranty terms |
How we recommend: For new ductless installations, we size a Mitsubishi Electric system to the rooms, outdoor design temperature and line-set layout. We continue to repair and service Daikin, Cooper & Hunter, Fujitsu, Bosch and other existing mini-splits.
Brands we avoid: No-name Amazon-listed brands with no US parts distribution. A failed compressor on a no-name brand can mean 8-12 week wait for parts versus 1-3 days for the brands above. We’ve seen this kill customer comfort in the middle of summer; we’d rather not put you through it.
As a Mitsubishi Electric Diamond Contractor, we register M-Series and P-Series installations within 90 days for the 12-year parts and compressor limited warranty. This applies to a single-family home while the original owner lives there, and is not transferable. Our workmanship warranty is 2 years. Read the warranty terms and optional extended labor coverage. Daikin central AC and ducted heat pump installations remain available.
Bay Area furnace and water-heater emission rules
Checked September 28, 2026. The Air District has separate rules for furnaces and water heaters. These are standards for covered new equipment, not a requirement to remove a working appliance.
- Furnaces, Rule 9-4: ultra-low-NOx limits apply to covered units manufactured after January 1, 2024; the adopted zero-NOx standard applies to covered units manufactured after January 1, 2029.
- Furnace scope: the rule defines furnaces with heat input below 175,000 BTU/h. Its separate 65,000 BTU/h threshold concerns the cooling capacity of combination heating/cooling units, not furnace heat input. Mobile-home furnaces are excluded.
- Water heaters and boilers, Rule 9-6: the adopted zero-NOx dates are January 1, 2027 for covered small tank water heaters and January 1, 2031 for covered larger equipment, based on manufacture date. Equipment limits and exemptions apply.
Water-heater changes proposed in 2026 are still under consideration. Before choosing replacement equipment, check the adopted furnace rule, water-heater rule and current Air District updates, along with your local permit requirements.
Frequently asked questions
Does a second-floor bedroom install cost more? +
Usually somewhat, and for three concrete reasons. The line-set run from the outdoor unit to an upstairs head is longer, so there is more copper, more insulation, and more labor in the wall or the chase. The wall penetration happens at height, which means ladder or scaffold work instead of standing on the ground. And condensate has to get out: on a first floor it usually gravity-drains through the wall, upstairs it sometimes needs a small condensate pump or careful routing down an exterior wall. None of this changes the equipment sizing the calculator gives you, and none of it is exotic work. We look at the actual wall on the assessment visit and put the exact number in writing before any install.
When does a mini-split make more sense than a central heat pump? +
Mini-split wins when (1) the home has no usable ductwork, (2) only certain rooms need conditioning (master suite, ADU, garage conversion, sunroom), (3) different rooms have very different load profiles, or (4) you want zone-by-zone temperature control without re-doing duct distribution. Central ducted heat pump wins when ducts already exist and are in decent shape, same registers, same return, the install is cleaner. We sometimes recommend hybrid: ducted main system plus a single mini-split head for one room the ducts can't serve well.
How is mini-split sizing different from central HVAC sizing? +
Mini-split sizes per zone, not whole-home. Each indoor head is matched to the BTU/h load of the room it serves. A 12,000 BTU/h head (1-ton equivalent) handles roughly 400-500 sqft of typical Bay Area construction. Outdoor units are spec'd to handle the combined connected load of all heads, with diversity factors that allow connecting more heads than the outdoor's nominal capacity since rooms rarely all peak at once. Our [free mini-split calculator](/free-mini-split-calculator/) sizes per room and recommends the right indoor head.
What rebates are available for Bay Area mini-split installs in 2026? +
MCE Heat Pump HVAC rebate for MCE customers in parts of Contra Costa, Marin, and Napa. PG&E thermostat rebate. EBCE/Ava program for Alameda County customers. Manufacturer instant rebates from Daikin and Mitsubishi when promos are active. Federal 25C expired December 31, 2025. Tech Clean California is currently on waitlist. BayREN heat pump cycles open and close, confirm when you're getting the quote. See our [California HVAC rebates 2026 guide](/blog/california-hvac-rebates-guide-2026/) for the active list.
Do mini-splits work in Bay Area winters? +
Yes, comfortably. Modern cold-climate mini-splits (Daikin Aurora, Mitsubishi Hyper-Heat, Cooper & Hunter PEAQ, Fujitsu Halcyon LX) deliver full rated capacity to 5°F outdoor and continue providing heat below that. Bay Area design heating temperatures range from 30°F (Tri-Valley CZ12) to 36°F (East Bay coast CZ3). Every cold-climate model is engineered for far harder conditions than we get here.
What about the BAAQMD gas-ban rules I keep hearing about? +
Rule 9-4 covers certain gas furnaces; Rule 9-6 covers water heaters and boilers. The adopted furnace rule sets a zero-NOx standard for covered units manufactured after January 1, 2029. It does not require replacing a working furnace. Equipment scope, manufacture date and local permit requirements matter. Water-heater amendments were proposed in 2026 and are not yet adopted; check the Air District rule information before choosing equipment.
Ready to plan a real install?
We size each zone on-site, walk you through equipment options, and write you a quote that holds for 30 days:
- Ductless mini-split installation: single-zone or multi-zone systems
- Central heat pump installation: if existing ducts are workable
- Full HVAC installation: new construction or full replacement
- Maintenance plans: extend equipment life
Related reading: Heat pump vs mini-split · California HVAC rebates 2026 · What heat pump installation actually costs · What size heat pump do you need.
Ready for a real estimate?
Licensed Bay Area HVAC contractor (CSLB #1136642). We’ll walk through your calculator results, check your panel capacity, and put it in writing.
(925) 999-4095Save your zone sizing
Run the calculator above, then export your zone-by-zone recommendation as a PDF for a contractor walkthrough or your own records.