Answers
How many mini split zones do I need?
Zone count is decided by doors, floors and how you use the house, not by bedroom count.
The short answer
Count the spaces air cannot reach, not the rooms. One head handles an open main floor well. Every closed door and every floor level argues for another zone. Most Bellingham houses we quote land between one and four heads, and the PSE rebate requires a head in the main living area.
Doors and floors, not bedrooms
A single wall-mounted head throws air across an open living-dining-kitchen space and does it cheaply. It will not push conditioned air down a hallway and around a closed bedroom door, and no fan setting fixes that. So the first question we ask in a walkthrough is which doors stay shut at night, because those are the rooms a single-head system will not serve.
Split-level and two-story houses in the 1950s–70s stock
Ramblers and split-entries from that era stack living space over a daylight basement or a crawlspace, and warm air does not travel downward. A daylight basement almost always needs its own head, and an upstairs bedroom wing usually does too. That is how a house you assumed was a two-zone job becomes a three-zone job on paper.
Fewer, larger heads is not automatically cheaper to run
A multi-zone outdoor unit modulates to whatever its connected heads are asking for, so when only one small bedroom head is calling, the compressor may run above its most efficient point. Sometimes two single-zone systems beat one four-zone system on both efficiency and repair exposure, since a single-zone failure does not take your whole house offline. We price both when the layout is close.
What the PSE rebate does to your zone plan
PSE’s electric-resistance conversion rebate requires at least one indoor head in the main living area, so a bedroom-only install does not qualify. It also requires the system to be fully ductless, including no short duct runs off a concealed indoor unit, which rules out the hybrid layouts people sometimes propose for a hallway. PSE further requires the installing contractor to be in its network; ask us to confirm status for your project before you count on the rebate.
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