UPDATED: Break
Even COP’s for MA
How do you know if you should install a
ductless mini-split, or upgrade your air-conditioner to a heat-pump and create
a dual-source application during replacement this Winter? I have been asked this countless times over the past week! I personally
always prefer the option of multiple fuel sources, particularly since energy
prices have been all over the place during the last decade. Fortunately, using
averaged energy prices, there is some simple math to figure out if an
aggressive assessment should be made for a dual-source heat pump application,
based on equations from ACCA's Manual H: "Heat Pump Systems: Principles
and Applications". First, you will need the average energy costs for
the selected fuels, and then plug the information into the equations
below. This will provide your "break-even COP", or the point
where operating the heat pump will cost the same as the other source. You
can then take the calculated Coefficient of Performance (COP) and see what
temperature the heat pump will be operating at; the lower the better!
I completed a little research for you, so
let us insert the recent average prices into the Natural Gas, Oil, and Propane
equations to see if the investment in a heat pump will make sense during
replacement, or become your primary source of heat – and to what temperature.
As you can see, if installing a 96%
Natural Gas furnace, the Break-Even COP would be 3.9. Based on the
Heating Performance Data for Fujitsu’s most efficient 12K RLS2 Heat Pump, it
would need to be above 60F outdoors for the cost to operate the heat pump to be
cheaper than the Natural Gas Furnace (see data at bottom, assuming 70F Indoor
Temperature).
Not all homes in MA are lucky to have
access to a Natural Gas supply. There are more than enough Oil Tanks out
there to keep the hundreds of delivery companies busy during most New England
winters. As you can see in the equation for oil, a resulting break-even
COP of 2.6 indicates a significant savings can be realized. Based on installing
an extremely efficient 87% oil furnace and the same heat pump performance data,
the heat pump would still be cheaper to operate as low as 20F. Of course,
you must worry about the output of the heat pump at that low ambient, and in
order to feel comfortable you will need to calculate the Thermal Balance Point.
If you decide to install a Propane tank
you could realize the same efficiencies as the natural gas furnaces out there,
but the increased costs in fuel/delivery is currently higher than oil, particularly
when including a recent oil price plunge. As you can see, the break even
COP for installing a heat pump add-on above a 96% Propane Furnace is only 1.45.
This is even lower than the Oil application, resulting in a break-even COP of
-15F, proving the recommendation of a more thorough calculation into the
Thermal Balance Point and investment costs for going to Dual Source.
With the
recent technological advancements in the HVAC industry in controls and
conventionally ducted VRF's like the Carrier GreenSpeed, break even COP's and
Thermal Balance Points can be driven even lower. This makes Dual Source
Heat pump applications more attracting to New England homeowners, despite
recent electric rate hikes. Some contractors are still installing
electric supplemental heat, hopefully in stages, for low-ambient
operation. Although not any more efficient than the heat strips it
replaced, the new heat pumps could save more than enough above the temperature
of the defrost cycle to still be worth it. I would still prefer
dual-source, you know these energy companies will not be leaving any money on
the table over the long run!
