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When many of us hear the words heat pump, we might think air-conditioner or refrigerator. It’s nothing new, it seems like old technology, but truth be told, heat pumps have been improving over the years; getting more efficient all of the time. For many of us, refrigerators don’t even sound environmentally friendly, but they could be! Heat pumps could make a huge difference in saving real energy required to heat homes and buildings.

Let’s start with a quick overview of the differences between Air to Air heat pumps and ‘Water to Air’ or ‘Water to Water’ heat pumps.

Air to Air heat pumps

These units work very much like an air conditioner but can also run in reverse to heat your house or building. The way they work is by transferring heat from the air outside into the air inside your home. Even when the air outside is cold (let’s say 10°C / 50°F) you can still warm your house to 25°C / 77°F.  It would cost four times (4x) as much to heat the same space using an electrical heater.

Unfortunately, when the outside temperature drops to below zero these units can no longer pull as much heat out of the outside air.  That’s when an electrical back up kicks in and heats up the air inside your house.  This decreases their overall efficiency, but they’re nevertheless efficient the rest of the year (fall, spring, and summer).

Water to Air or Water to Water heat pumps

These are a whole lot different because their source of heat is not the outside air temperature, but instead, the ground temperature underneath or near your house. The ground temperature remains relatively constant even during a Canadian winter.

If the water going into a heat pump is above freezing*, the heat pump can suck degrees out of the water and transfer that energy into hot air or hot water.  This hot air or hot water can then be used to keep your house warm.  These units work by adding a small amount of heat over a longer period of time compared to a gas or oil furnace.  So, if you opened your front door long enough in the middle of winter and the house temperature dropped suddenly, a back up electrical heater kicks in to quickly raise the temperature.  Of course, this costs more money to run and you want to avoid that sort of thing.  In my experience, the electric backup heater only kicked on once or twice for about half an hour during a winter season.  Overall, I’d say the heat pump furnace probably reduced my electricity bill by more than half (probably close to a quarter).  More details about the residential geothermal heat pump experience.

The absolute best choice for keeping your house an even temperature is thermal mass (with or without a heat pump). Your house can act like a passive solar collector. The thermal mass around and at the center of the house will radiate energy back into the home during the night after it has ‘charged’ up from solar exposure during the day. If building from scratch is not an option there are small modifications that you can make to reduce the amount of energy and the amount of money you spend to keep your home warm and lit.

*note: a closed looped system can also be filled with anti-freeze.

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