Air-Source Heat Pumps – Cost-effective, Convenient – and Very Green

The presenter has lived in Hingham for 32 years in an old, eight-room New England farmhouse built in 1880, which he and his wife have extensively renovated. An inveterate do-it-yourselfer, sailor, musician, songwriter and vegan cook, John had to replace his heating system when the old steam boiler cracked at the end of the winter in 2018. He consulted six contractors and evaluated both gas-fired and air source heat pump solutions. Having invested in solar panels the year before, he wanted to use his $5,000 solar credit from the Hingham Municipal Light Plant to help defray his heating costs. Initially steered away from heat pumps by prominent HVAC contractors, he independently researched this technology and developed a design incorporating a detailed floor plan of his home with square footage and calculated BTU requirements for each room. Using on-line resources, he was able to specify and price the appropriately sized Mitsubishi components and developed a proposed configuration as a basis for discussions. Proposals ranged from $56,500 for a traditional gas fired solution to $22,800 for a heat pump system (the winning bid from Coastal Heating and AC). Installation took only one day! John and his wife are delighted with the results – a state-of-the-art heating and cooling system. Each room is a discrete “zone” featuring year-round climate control at the touch of a button. The flexibility, convenience and cost of the system could not be matched by older technologies. This electric-powered, highly efficient solution was not only the least expensive, it was the greenest by far of all feasible options and, as the HMLP’s sustainable sourcing increases, the house’s carbon footprint will continue to shrink. Key metrics include the following:

  • Total annual energy usage decreased by a factor of 2.59! (I.e., 2018 usage was 2.59 times 2019.)
  • Usage of environmentally detrimental natural gas declined by 98% – from 1,853 Therms to 45!
  • Although cost per unit of energy almost tripled (electricity costs more than equivalent gas), total annual energy costs increased by only @$150 per year (a 3.76% increase on a base of @$4,000).
  • This is a trivial cost increase more than offset by the fact that the system cost $9,000 less than the lowest gas-fired bid. (E.g., $9,000 spread over 30 years is $300/year.)
  • The system qualifies for Alternative Energy Credits (AEC’s) under the APS Renewable Thermal program of the Mass Clean Energy Center (MassCEC), further offsetting operating costs.
  • Best of all: even without factoring in the solar panels, the carbon footprint of the house decreased by almost 50%! (Previously installed solar panels generated 40% of the electricity used in 2019.)

The air inside the house is cleaner, since each room unit has an anti-microbial dust filter. Dedicated remote control units for each room’s internal air exchanger (aka “mini-split”) allow fine tuning of temperature, humidity, fan speed, direction of airflow, etc. Different settings can be programmed for different times each day. You may have seen air-source heat pumps on This Old House and elsewhere. This is great technology!

Presentation Slides

If you would like to talk with someone with personal experience who can answer questions, a Climate Coach is available. To reach a local citizen who can help, click here.