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There have been many discussions on heat pumps and furnaces/boilers, so I thought I would put out some of the points that seem to keep recurring.

Heat Pumps in Cold Climates: Why Hybrid Systems Make More Sense: Heat pumps are a remarkable technology, but in cold climates with high electricity rates, they can be expensive to install, replace, and run. Fortunately, hybrid systems with a boiler or furnace offer a smarter, more flexible solution.

Bosch recommends mini splits with boilers, not just heat pumps alone.  In a training session two weeks ago, they also stated that heat pumps in New England are not a good application because the electric rates are so high.

NREL study shows a seasonal COP of 2.1 (210% annual efficiency) - that's almost $6/gal oil equivalent. Since the COP drops further with lower temperatures, electric bills increase rapidly. This May 2023 NREL Field Validation of Air-Source Heat Pumps for Cold Climates study shows the wide disparity between manufacturers ratings and field performance, with an average seasonal efficiency (COP) of 2.1. On a unit of energy basis, $0.30/kWh is the equivalent of $12.18 per gallon of oil and $8.79 per therm of natural gas. New York residential electric rates increased 50% from 2020 to 2024, and 4% in the prior 7 years…Northeast states are leading that trend and forecast to increase further.

Studies show 60% to 80% of people turn off their heat pump below 35°F, often due to high electric bills and the air the blow is colder than furnaces (multiple studies p 18-19). That’s often the right choice economically and environmentally because furnaces and boilers will cost less to operate and they use less source energy compared to electricity generated with natural gas (EPA Clean Air Markets Program Data CAMPD 40% power plant efficiency in New England less 8% transmission and distribution losses); and they have lower carbon intensity (GREET 2022 1.06% natural gas fugitive emissions means natural gas 20 year lifecycle has a 36% higher carbon intensity than fuel oil). Even more so when temperatures drop below freezing.

Imagine a power plant as a hungry pizza eater. You feed it 8 slices of natural gas, but it gobbles up 5 slices just to generate and deliver electricity to your home. That leaves only 3 slices of usable energy. A 210% efficient heat pump can stretch those 3 slices into 6 slices of heat. But if you use a boiler that's 87% efficient, it skips the power plant altogether and turns 7 out of 8 slices directly into heat, more warmth, less waste.

Furnaces and boilers deliver warmer, more comfortable heat (cold climate technical data p A230). For comparison, the air leaving mini split heat pump heat at 91°F can feel like cold air blowing at 73°F just a few feet away. A better air sealed and weatherized house with high efficiency windows and doors can improve winter heat pump comfort.

Electrification will require that the residential grid grow 4X. Cold climate heat pumps consume close to 2X as much electricity as a typical home, and EVs use the equivalent of another home's worth of electricity. In the near term, that means if just 10% of cold climate homes fully "electrify", the residential grid will need to provide almost 30% more electricity (and that does not include overall grid load impacts from AI impacts). And the cost of utility scale battery back up is astronomical, they last about 10 years and cost about $300 to $500 per kWh of storage - that's just $0.30 of electricity.

Heat pumps aren’t just expensive to run, they’re expensive to install and replace. In Rhode Island, representatives indicated that converting low-income homes to heat pumps cost the state $20,000–$25,000 per home this year. Over time, that’s $75,000+, compared to a single boiler that lasts decades.

Hybrid systems make sense, especially in a volatile energy future. It’s not all-or-nothing as hybrid systems let you choose the best tool for the job, season by season. Choosing to heat with a heat pump or a boiler/furnace could be for personal comfort, operating cost, emissions, source energy consumption, and more.

Roger

Hi, I use REMS for bending and tube expansion. A neat thing about the long bends you get is that the water doesn't know it's changing direction with bends over five pipe diameters, so no real turbulance or friction loss. This helps prevent erosion and can even allow you to use smaller pipe in some cases. Good way to go.

Yours, Larry