Efficiency Maine Heating Cost by Fuel Type - Any good?

AdamInEvergreen

https://www.efficiencymaine.com/at-home/heating-cost-comparison/

Basically the way you use the calculator is get your average fuel price for a given period (whatever you one) and then use the increase or decrease buttons to match your annual cost.

I have propane receipts for 2/22/20 to 2/27/21 which have an average of $1.50/gallon. Hit the "increase" button until the annual cost show in red matches my cost for that period.


They have a bunch of fuel types in there but I want to compare it to installing mini splits. Except changing the kWh to match my power bill I didn't change anything else:


Sooo...the calculator seems to be calculating your heating load in BTUs on the back end and then converting that back to dollars given your inputs on system info. Is that an effective way to do this?

The website pre populated the 293% system efficiency...basically it appears to be dividing the 3,412 btus/kWh (which is basic electric resistance heat) by the system efficiency. How do I turn a HSPF number (or something else I can find listed, LG Art Cool at 13.5 HSPF for example) for one of the units I'm looking at in to this "System Efficiency" number?

Thank you!

Edit: original post I accidentally did SEER rather than hspf.

Jamie Hall

Going to heating load in BTUs and then basing comparisons on that is no only an effective way to do it -- it's the only reliable way. Good for them.

I suspect that that 293% figure is actually derived from the COP -- coefficient of performance -- of the heat pump, and they do vary. The SEER rating is for air conditioning. The CP should be quoted somewhere, but it can be a bit tricky, since it varies with outside air temperature -- and the colder it is, the smaller the number will be. Also be very aware of what the coldest outside temperature the system will work at -- some units go much lower than others, but it's often suggested that you may want back up fuel or electric resistance heat at air temperatures much below 20 to 30.

Hot_water_fan

Basically you’re taking $/random unit and then doing unit conversions to transform it into $/1,000,000 btus (MMBtu), a meaningful number for comparison. 

Then you’re dividing by COP of the appliance.
The calculator turns it into an annual number. 

So for mini splits: $/kwh x 1 kwh/3412 btus x 1,000,000 divided by COP. 

The 2.93 COP prepopulated is on the lower side, but should work well enough. As you can see, propane is much more expensive compared to heat pumps with $.13/kwh electricity with much lower emissions. The cold climate heat pumps can operate well under 0, so you may never need backup heat. Depends on the house’s heat loss though. 

AdamInEvergreen

Thanks guys... Sorry I accidentally did SEER instead of HSPF in the original post. I updated it. 

It seems mime HSPF is listed often whereas COP is not. So maybe my question is how to use HSPF in that calculation appropriately... I like the concept of incorporating efficiency losses caused by lower temperatures, but also it seems like that would vary a lot.

Here's a high end one I like as an example:
https://www.ecomfort.com/LG-LA150HYV3/p106687.html

Hot_water_fan

LG has engineering manuals with outputs and inputs at different temperatures and possibly different modulations (can’t recall, Mitsubishi does for sure). You can figure out COP from there after you match temperature to heat loss. The heat pump will be more efficient basically always. If you need backup heat at some outdoor temps (that’s a maybe), the propane will be cheaper for those few hours.