I quite like the Stelrad one.    

https://www.stelrad.com/advice-hub/heat-loss-programmes/

I’ve used the freedom spreadsheet for my own place and am halfway through doing the calcs for my builder friend on the same. 

I’ve also modelled my place in heatpunk, that’s quite nice, although not as fast as the freedom toolkit.

I have used the stelrad windows program for rad sizing but haven’t looked at their other offerings yet, will do so.

@hughf, is the Freedom one free to download?

Posted by: @editor

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@hughf, is the Freedom one free to download?

They were sending copies out to anyone go asked for a while, not sure what the current situation is as they’ve taken down the video instructions from their YouTube channel. I’ve since stuffed it in my GitHub which is probably against various terms of use but I’ll deal with that issue if it ever arises.

Posted by: @editor

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is the Freedom one free to download?

It used to be (from the Freedom Heat Pump's website) but you now have to create an account (I wonder why) which I declined to do as it is not clear what that involves or what it gives you access to. The Wayback Machine does not appear to have the actual downloads, though it does have the folders. But all is not lost, a copy of v3.3 (early 2022) is available on this very forum!

https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/designing-ashp-system-using-the-freedom-toolkit-spreadsheet#post-8477

Posted by: @hughf

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they’ve taken down the video instructions from their YouTube channel

Looks like the cancel culture has hit Headroom Heatpumps... 

@cathoderay freedoms 2.1V is the one in my signature (Google sheets version)

@cathoderay, brilliant, I've re-uploaded here for easy access and reference.

@editor - it was just hiding in plain sight, as things so often are!

People do need to be aware that, while good, Freedom's calculator is not perfect:

(1) famously, it over-estimates Midea heat pump output at lower ambient temps

(2) not all building materials are available, sometimes you have to choose something that is not what you home has, but is 'near enough'

(3) it uses a relatively crude method of calculation radiator output (based on area) which doesn't take into account an actual radiator's output (but most of the time it is 'good enough'). It also lacks the option of using K3 rads (but you can hack it to make it do that, but make sure you get the numbers right)

(4) v3.3 uses/tests for the MCS heat pump must supply 100% or more of the heat demand requirement (if it doesn't you FAIL). I think MCS in their infinite wisdom may have changed that requirement. Perhaps someone more up to date on MCS requirements could comment

Lastly, it needs a LOT of data entry. Typos are easy, check and double check your entries, and do visual sanity checks on your results eg if a large room has a small heat loss, you probably made a typo in a measurement entry somewhere. 

Does anyone else get a "Problem with content in this workbook" error when opening this file in Excel?  I am using Excel 2016

@abernyte - I use LibreOffice Calc. Maybe try that?