Traditionally, standard air-to-air heat pumps have been a dirty word in the Northeast. High electricity rates and poor performance at low outdoor temperatures have made new installations of air-source heat pumps an almost taboo practice. But several factors have caused contractors (including us) to take another look at air-to-air heat pumps.
The biggest knock against air-source heat pumps is the fact that their heat-output drops substantially once the outdoor temperatures gets below approx. 30 degrees F. Below 30 degrees or so, a secondary heat source must be utilized. Traditionally, this secondary heat source has been electric strip-heaters -- very expensive to operate -- and hence the unpopularity of air-to-air heat pumps.
Now that heating oil has broken the $5.00 / gallon barrier, heat pumps have gotten a second look. By utilizing heat pumps in a dual-fuel heating strategy, we can use them where they work best -- at temperatures above 30 degrees -- and utilize heating oil or propane as the secondary fuel instead of electric strip-heaters.
Above 30 degrees F, air-source heat pumps work exceptionally well in terms of cost-efficiency. Moreover, more than two-thirds of our heating season (upstate NY) is spent at temperatures above 30 degrees F. For the remaining one-third of the season, we can switch over to oil or propane.
This "dual-fuel heating" option results in an operational cost-savings of 30 to 40 percent over typical oil-fired equipment.
To make the switch-over from heat pump to fossil-fuel furnace (or boiler) automatic, one can use a traditional two-stage heat pump thermostat, or go one step further with a specialized control, such as the Bill Porter Dual Fuel Kit.
Another factor making heat pumps more attractive in the Northeast is the increasing trend toward "cold-climate" heat pumps. A small handful of manufacturers have developed air-source heat pumps capable of operating at sub-zero temperatures. Manufacturers of cold-climate heat pumps include Hallowell International and Mitsubishi Electric .
Cold-climate heat-pumps are capable of carrying the entire heat-load of the home at temperatures as low as -14 F degrees, rarely needing a secondary heat-source.
Heat pumps are one of the most cost-effective upgrades one can make if they are currently using heating oil or propane as their primary fuel.
