Skip to main content

Heat Pumps – Not a Weapon of Mass Destruction

By April 21, 2014November 7th, 2021Energy Efficiency, Energy Rant

In the 1970s, before STAR WARS, my childhood fantasy sci-fi favorite was Planet of the Apes[1].  Like STAR WARS, there were about five movies in the series, but I only remember the story lines of the first two.  Three guys travel through time in a space ship, supposedly light years away.  They land on a planet that is actually California, ironically (can tell from the landscape, and hey, movies were once made in California).  It is several centuries into the future as it turns out, and on the Planet of the Apes, the apes talked (in English of course) and evolved from the mute man, which as it turns out, wiped out the planet with a nuclear war all those centuries ago.

In the second movie, Beneath the Planet of the Apes, much of the action occurs below ground, supposedly in the New York subway system where superhuman talking humans, I guess, live.  Who knows what they ate or where the power to light their tunnels and wash their robes came from.  But the part that cracked me up was their worship of a nuclear bomb – in shiny gold casing of course.  “Glory be to the bomb and its holy fallout.  As it was in the beginning, is now and ever shall be; world without end; Amen.”

The cliché, one size does not fit all, applies to nothing more than energy efficient solutions for end users of all types; residential through large industrial.  But yet it seems some technologies reach bomb-like status, and if you point out any shortcomings, blasphemy!  You heretic!  Cool and logical heads do not prevail, which is the whole point of the Planet of the Apes series.  First, the human species goes off the deep end and destroys itself, and then they evolve to worship the tool of destruction.

READ THIS: supporting certain energy efficiency, fuel, and generation is not in any way close to the craze of worshiping a high caliber bullet that is dressed up to look like a bomb.

Several years ago, Michaels was awarded a broad sweeping study for the cost effectiveness of ground source heat pumps for the state of Minnesota.  This mandate actually came down through the legislature.  We completed our study, and our analysis showed the bomb, er excuse me, the heat pumps were not the most cost effective solution for all applications; particularly for stand-alone homes when compared to conventional natural gas heating and air source cooling.  The study is available here.

The folks we were working with from the state approved it and agreed with the findings prior to its release.  Some in the “special interest” heat pump industry that supported the state funding of the study kind of came unhinged when they found our results.  As I say often, “Sorry, they don’t make the meter spin in reverse.”

Any energy engineer worth anything can and should do a “bracketing calculation” to determine if the savings estimates from a sophisticated building simulation, which the results were based on, make sense.

To wit, the cost of providing a million Btu of heat with a ground source heat pump with a COP of 5.0 (that’s like a SEER of about 20) is shown in Figure 1.  The COP is the third term showing 5 Btu of thermal energy (heat) delivered for each Btu of electric energy.

For natural gas, the cost to deliver one million Btu of heat is shown in Figure 2 above.

This demonstrates that heat pumps indeed cost less in terms of energy operating cost.  And if electricity is produced with natural gas, they even produce less carbon dioxide to heat homes.

The problem for the bomb, er heat pumps, is they are very expensive compared to a gas furnace – in the $12,000 extra range.  The Achilles heel of ground source heat pumps is the holes in the ground, which aren’t going to get cheaper from technology that I know of.  It’s a primitive, labor-intensive process.  We’re not digging for natural gas and oil.  We’re digging for heat transfer only.

If I take typical numbers for an upper Midwest home, say 1500 therm per year to heat with a furnace, the savings come to about $700 per year.  That is significant.  But I can see by doing the math in my head, that is a 20 year simple payback.  This is not cost effective compared to something like making a larger down-payment on the purchase of a home or car; i.e., the cost of money.

Our study did show heat pumps to be more cost effective than large central systems for some commercial buildings.  Energy-wise, they are great, but they (it’s difficult to resist) are no silver and gold bullet.  Ironically, I’ve said for years, that ground source heat pumps have cult-like status in some jurisdictions.

Certainly, there are other bomb-like idols in the world of energy efficiency and renewable energy.  I’ll write about more of them down the road.

[1] They had action figure toys, villages, and the whole nine yards.

Jeff Ihnen

Author Jeff Ihnen

More posts by Jeff Ihnen

Join the discussion 2 Comments

  • chitown_nick says:

    Good to see that report getting some positive spin. A couple notes even on the quick math: The efficiency of the gas heat should be /0.9 instead of *0.9. Minor result change, but technically that’s how it goes. So you get to $11.11 compared to the $6.44.

    The real kicker come in when you look at the current drop in natural gas costs – maybe $0.60 per therm these days. Now it’s $6.67 vs $6.44. That payback is getting close to infinite at today’s prices. No free lunch.

    • Jeff Ihnen says:

      Thanks for pointing out that error, Nick. We’re fixing that. You are correct with the numbers / prices. I used a recent “worst case” price.

Leave a Reply