Should we update the default HeatpumpMonitor.org stats period to 90 days?

As we enter warmer months and have many more systems on the site, should we extend the default HeatpumpMonitor.org stats period to 90 days? Perhaps this could be extended gradually over the coming year so that in 6-9 months time it only shows systems with a full year of data on the default view? Giving a more accurate idea of what real world performance is over a full year for those accessing the site at a glance?

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Yes this sounds sensible.
There are now over 84 heat pumps with sufficient data to be representative of the last 90days, I am taking the cut-off for that to be 86days (out of the last 90, ie 95% data availability).

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Yes, a longer period would give a more representative view of performance.

It might also be useful to have shortcut for the “winter heating season”, i.e. fixed 120 days from November through to February.

We should look carefully at which numbers are marked as “SCOP” - this term should only be used for exactly 365 days of data. For instance, the number shown at the bottom of My Heatpump app next to Total Electricity input and Total Heat output shouldn’t be labeled as SCOP. Better to call this “Overall COP”.

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I thought the S in SCOP stood for Seasonal, although I have never found a definition for this. I wouldn’t have thought that reserving this for a 365 day period makes sense. This should be referred to as ACOP.

As I don’t use the heat pump between late April and early October, what happens when I stop uploading data? Do I need to notify anyone?

Most monitoring systems are 365 24x7 which would imply you actively stop uploading? Why?

COP varies throughout the year, depending on the outdoor temperature and humidity. So, in order to compare heatpumps, SCOP or SPF (Seasonal Performance Factor) is quoted using the total heat production ÷ electrical consumption over the entire heating season, i.e. one year.

(Particularly if the heatpump is used through the summer to heat water; one could get away with shorter periods if the heat pump is off for part of the year, but it’s simpler to use the same 1 year for everyone)

If SCOP is calculated over a period that includes 2 winters and 1 summer, the result will be skewed. Same for a period covering 1 winter and 2 summers. So, for an accurate measure of performance, this should be done over a whole number of years.

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Thanks all

Having switched this to 90 days for a couple of days without a proper announcement and in view of the flurry of messages to the effect of ‘why has my system disappeared?’ I wonder if we need to find a better way of indicating the stats period and switching between them.

One option would be to change the stats time period selector from a dropdown to a group of buttons at the top of the table which might be a clearer way of indicating that a different stats period has been selected?

It’s hard to balance here that on the one hand we should be highlighting the full year stats period as the most accurate reflection of real world SCOP performance and on the other that half the fun for a lot of people contributing systems is to see their system listed without having to wait too long a period…

how to get the right balance?

He he, yes whatever is selected as default is a little arbitrary, but being able to change parameters and graph/compare is fantastic, thanks.

I guess a value/protocol that matches as close as possible the way installations are evaluated elsewhere would be useful to third parties looking for easy to access performance data. Maybe a separate COP entry under ‘Top of the SCOPs’ where ‘Top of the SCOPs’ uses the industry agreed periods & parameters and the ‘COP’ allows the same/similar parameter selection as current?

I think the Heatpump + Fabric display is a useful way to look at over-all building efficiency all be it not all buildings are heated to the same temperature. I guess it depends where people want to set/define system boundaries.

Whatever is defaulted, there will be opportunities to play - as long as pumps have non-linear output/efficiency curves, SCOP can be boosted by running hotter than needed in the shoulder months. It puts the pump in an efficient state, avoiding too much cycling, but is certainly not the most efficiency over-all way to heat the building.