GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Mini split sizing

bertmatter | Posted in Energy Efficiency and Durability on

We are looking to add a mini split to replace electric  baseboard heating . Located in Langley  BC.
January February mean daytime temperature is 36 F, night time 33F, night time  temperatures go below  freezing maybe 15-20 times all winter and only to the high 20’s F.

We live in a 2nd floor  in law suite around  750 – 800 square feet , open concept  kitchen family room, an additional  bedroom  is not heated as it stays between  58-65F.
Presently heated with2-500watt and 1- 1250 watt electric  baseboard  heaters (3413×2.25=7679btu).
Night time setback to 62F, daytime 69F, however  it generally takes2-3 hours to bring it back up in the  morning. Only  a  few times a winter does it get somewhat cold into the low to mid 20’s, then a plug in electric heater is used to bring the temperature  back up quicker  in the  morning. 

So I am looking at Gree 9000 btu and a Gree 12000 btu .Specs for 9000btu: cooling cap;1535-12966,heating  cap:2388-13648, seer:38 hspf;15.

12000 btu specs:cooling cap:3,100- 13,000, heating  cap: 3,071- 18,766, seer: 30.5, hspf :14

When I look at hvac internet  sites they recommend 9000btu for less than 400 sq feet , 12,000 btu 5-600 sq feet.

Am I missing  something  here? I think  either one would do as they  both modulate  quite low in heating (2388 &3071) .

Any thoughts  would be appreciated!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. willymo | | #1

    You need to figure out your heat loss before any decisions. See many other posts here on how to do it.

  2. Expert Member
    Dana Dorsett | | #2

    At your fairly temperate -5C heating design temp just about any 9000BTU mini-split would cover the entire load, as you correctly surmise from the maximum output numbers of your existing baseboards that are doing the job.

    For reference, Vancouver Airport's 99% design temp is +25F/-4C :

    With a mini-split it's less efficient to use deep overnight setbacks. Using set backs it'll use a bit less than half what the baseboards use, but if you "set and forget", tweaking it up or down only a degree or two at a time it'll use just a third or less.

    1. bertmatter | | #3

      Thank you for the confirmation Dana, I have read many Q&A columns over the years and I have read many times yhe importance to size it correctly.
      So the 9000 btu model would be the better choice over the 12000 btu model as the seer &hspf is higher?

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |