We currently have a central AC unit and oil furnace. The AC is broken and the furnace is old, so we are thinking of replacing both sometime in the next year.
We are considering replacing the AC with a heat pump and the oil furnace with a gas furnace in the hopes that the gas company will bring a line down our street from the main road sometime before the furnace needs to be replaced.
From my understanding, the heat pump could also be used to heat the house up to a certain point in the winter.
I don't know a whole lot about heat pumps, so I'm wondering how effective a heat pump would be at cooling and heating the house (currently just the first floor, about 800 sq ft, and basement), both in terms of cost effectiveness and actual comfort level of the house. Should a pump be able to cool our house on 100+ degree days to, say, 70-75 degrees? Will it be able to get our house warm enough in the winter in a reasonable amount of time?
I'm told the units will somehow be set so that the furnace kicks in automatically when needed, but I'm wondering how that is actually determined. I don't want to be sitting in a cold house for hours waiting for the furnace to realize the heat pump isn't going to do the job.
I've also heard the pump is cheaper for heating, but I am wondering about the specifics. How much cheaper would a heat pump be to run? Both run on electricity to some extent, but does the heat pump use more electricity to warm the house than the furnace, and, if so, is it enough to make up for the cost difference?
Any other pros/cons I should be thinking about?
Best Answer
You don't have to worry about a heat pump being inadequate for cooling tasks, they are available in a large range of sizes. For really large buildings, they can be ganged together. 800 sf is a walk in the park for residential sized units.
I don't know the specifics of what determines when the backup furnace kicks in. IIRC, it is the combination of a lower thermostat set point and the outside temperature. It kicks on when the pump is not keeping up or it's too cold for it to run efficiently. I can assure you you will not be sitting for hours waiting for backup heat. No customer would sit still for such a system.
While it is true that heat pump heat is free, you are just paying to move it around, if you've had heat wave cooling bills before, you know moving heat around is far from cheap. Only a careful analysis of the various options, considering both operational and installation costs, as well as life cycle replacement, can you make a proper decision about which system is most cost effective. The correct solution will vary by small changes in energy costs and climate.
In cold climates, a ground heat source system should at least be considered because it will reduce or eliminate the need for backup heat. If you are concerned about your carbon footprint, do not forget most electricity generated in the US is by burning fossil fuels. Your footprint from using a heat pump will vary greatly depending on where your local power is coming from. Heat pumps make a lot of sense for many people, especially if they are investing in cooling equipment anyway. But everyone's situation is unique, so the best solution can be arrived at only after careful rational analysis of all the factors.