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It is a toss up at best. Fossil fuel rate changes are immediately affected by market rates. Electrical rate changes have a longer lag time usually.

Sixteen years ago, when I installed a hybrid system in my home it was cheaper. I had advised that that was the best way to go.

Earlier this year I had a client who used oil for heat & electric AC inquire about converting to all electric. Of coarse I said that was foolish but I plugged the numbers into Carrier's operating cost calculator at her request. This incorporates the cost of fossil fuels, electric rates, the climate zone & the required BTUH for heating/cooling degree days for the area in question.

Imagine my astonishment when the numbers came up saving several hundred dollars as all electric. Oil @ $4.00 gal, Electric @ $ .095 KWHR this past season.

To verify accuracy of the program, I plugged the numbers in for my house using $ 3.25 gal for LP & the same rate for electric. The calculated cost for my hybrid system was within $ 20 of my actual cost. The all electric calculation showed over $ 1200 LESS per year as all electric.

WTF? I started inquiries with my clients with similiar BTUH loads & all electric systems vs. hybrid & came up with cheaper all electric cost everytime. We all had similiar desired comfort levels, (Tstat settings)

I was taught when using Manual J to upsize 1/2 ton as fudge factor for cooling because of builders not actually producing the tight, well insulated house represented along with the rapid degrading of window & door seals. I have observed over my career that oversized for cooling heat pumps installed by others have produced lower auxilliary heat use.

I have been spec'ing 1/2 to 1 ton over Manual J when using a variable speed fan coil & thermistat with DeHum capabilites for a few years just for the increased heating of the larger unit, for heat reducing aux. heat use. DeHum allows the AC side to get to desired RH.

This what I'm going to install in my aunt's (2nd Mom) home 400 miles away. That' what will be installed when I upgrade my home next year.
 
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