Sunday, February 26, 2023


I ran into the dad of one of the kids Kubota played soccer with.

He is in HVAC and we stood in the cereal aisle of the local grocery store catching up on the last year.

I asked him his opinion about about geo-thermal systems.

Loud: the compressor is in your basement

Still need a back-up heating system because most systems in Michigan do not have enough ground-loop to get through the entire winter

Work great for air conditioning but they are loud

They don't work when the electricity is off. You might be able to run a conventional furnace with the output of your generator but unlikely to be able to run the heat-pump on your geo-thermal.

They are expensive....and you still need the back-up system.

They are loud.

The alternative to the ground-loop is a double-well system where water is removed from one well and reinjected in the other. That is more expensive than the ground-loop system but does not hit saturation over the winter.

I asked about the energy savings.

My friend said, "Most people put in electric, resistance heating (baseboards) for back-up heat. Sure, they might save money at the beginning and middle of winter, but the dial on the meter sure spins fast at the end of it."


I am curious about how the folks who had significant solar made out during the outage.

I am 99.9% sure that they have to automatically stop feeding to the grid when it goes down so workers do not get electrocuted. But how many of them are wired so the supply can flow directly to the house's base-load?

In a perfect universe, the controller would have a hierarchy and would drop-out the low value load and feed the high value.

Spotting wildlife

Q: Did you spot the leopard standing on the rock?

A: No, it was already spotted when I popped open ERJ's blog.


  1. Pellet stove with a non-interruptable power supply and a couple large lithium batteries charged off the mains. The batteries could run the fridge as well, so you can shut the generator that is running due to a power outage off at night. That's what I would do.

    If you got all that money get a gas fired boiler with pex tubing in the floors and walls for radiant heat.

  2. How about as part of your heating solar hot water/thermal siphon and add to radiant heating system,make collectors with older but seal still good double glazed patio door sliders,a lot out on net on this.

  3. My experience with geothermal has not been as he described. I put in 7 wells vs a ground loop, the wells cost $7,000, the water furnace brand unit is very quiet all we hear is air moving through the ducts and maybe a low hum, ( it’s located directly under the kitchen floor in the crawl space.).
    A properly sized ground loop, or pond or series of wells will not get “exhausted”. If it does it wasn’t sized properly to begin with or you went cheap on insulation.
    Cost wise, when we put ours in, after factoring in the 30% energy efficiency tax rebate) we spent about $5000 more than a gas heating system with a separate air-con unit. This was on a 4200 sqft home and w saved enough on our energy bills to have an estimated 5 yr payoff. To my knowledge the emergency electric coil heat backup on the water furnace has never switched on .
    It would take a 20kw generator to kick the unit on so instead we have a wood burner standing by in the basement.

  4. pretty much you are about 300 miles too far north to use ground loop heating...unless you have a really large lake to use as a heat store or build your loop much larger than most of them are made....
    You don't need to have the compressor in the basement. It is just the way that most manufacturers set the system up. And most HVAC folks are just installers of prepackaged systems rather than folks that can design and build one on their own.

    The working fluid is what goes underground, The system is just a freon/glycol heat exchanger to pass the heat (or cold) to the glycol which then transfers the heat (cold) to the underground. and otherwise works like any other heat pump system.
    Build a big enough system (or a properly deep enough one) and you will not run out of heat.

    1. What B says.
      Can't say I have much knowledge of geo thermal, but "location, location ,location"
      Don't let a slick salesman sell you geo or the other "green crap"
      Most of the solar home systems don't work when the power is off (OH the irony when people find that out) To make that work, it's an expensive upgrade.

    2. Grid tied solar electric is Generally designed to be disabled when the grid is down.

      Protects the line workers restoring the power lines.

      My neighbor has found out that his grid tie system leaves him in the dark more than a few times in the past few years.

  5. Grid tie inverters are required to have anti-islanding feature which prevent them from turning on in event of a grid failure. I asked the question can you fool the inverter to turn on with a standby generator. The answer was prolly not since the average gen set is no where near omnidirectional stable enough. But you can get a gen set that is stable enough. Next problem is you have to be able to absorb all the power your grid tie system produces. Much much better to have a hybrid inverter hooked to battery bank and grid. Best of both systems, but expensive.

    1. To the best of my knowledge (which is sketchy at best) you would need to have a battery storage unit for when the power goes out

  6. I have a triple system. Grid tie, storage batteries, dedicated loads.when grid goes down grid tie stops working. System switches to a storage/dedicated loads with non-profit tie inverter

    1. That's what I would like - along with an east-west oriented roof not shaded by trees. Dammit.

    2. yes it is handy. In central Maine. About 2KW panels on roof. Make about 30% of my monthly KW usage. Keep Grid-tie to minimum and run Storage at night to cancel house loads. The trick is to "never" put anything out on grid

  7. We had a battery backed system that protected 4 circuits, mostly due to cookie-cutter design rules. We had 2.6 KW of solar cells, a 6 KW Inverter, and 10 KW-hr of battery to support a house with an running load of around 500W. The system could have run the full house but the manufacturer (Solar Edge) didn't provide a big enough transfer switch.

  8. Solar array installed on the barn roof (the unit can be amortized as part of the farm that way) tied to a solar battery in the barn. When the grid goes down the battery automatically kicks on to power 3 rooms in the house and the well. The battery lasts 2-3 days even if zero solar recharge. At that point flip one switch - explicitly wired and labeled - and the propane generator comes on. Plan is to only run that long enough for the solar battery to charge then switch back. So far the longest outage was three days but the longest outage in the past 20 years was two weeks. Located 2 farms from the end of the line so any issue up line affects us

  9. 1.5 kw solar, optima battery bank and a wonderful little woodstove in the living room.
    Happiness, a little East of Paris

  10. We have a ground water heat pump in Michigan (along I-94), and have had it in our home for 19 years. Our builder recommended we put in a back-up heat system, but it was out of stock at the time, and we never put it in. We have never needed it. Even when the temperatures outside get to -20 F outside, the system works fine. We spend the same amount on electricity in the winter as a lot of people spend on gas. And air conditioning in the summer is only the cost of running the fan.
    It is hard to retrofit a house to a heat pump because it requires double the amount of duct work and vents as a gas furnace. Someone who doesn't understand heat pumps will tend to undersize the system and it won't work properly.
    As far as the noise, it is louder than a conventional furnace, but I can only hear it when I am in the basement in the same room with it.
    The only real problem with the ground water heat pump is if we lose electricity, we lose heat.

  11. I've wondered about using underground, hyper-insulated (~R 120) water tanks for thermal storage, the water heated by solar water panels. 1 BTU = 1 lb of water 1 degree F, so 3,000 gallons of water heated to 150F is 70 degrees above radiant floor circulating (80F) = ~1,750,000 BTU. Power the circulating pump(s) with PV panels, and operating cost would be whatever annual maintenance is.

    The system would be very heavily insulation-dependent, both on water transport and storage insulation and structure insulation and air infiltration control, but, like the panels, tanks and pumps, that's a capital investment at construction rather than ongoing, and unknown, demand, cost and availability fluctuations, and probably not too much greater than high quality, high efficient structural space today equipped with PV panels and batteries.

    If the hyper-insulated underground vault was constructed under a patio adjacent to the structure it would not intrude on living space and would still be accessible for maintenance and replacement.

    Somehow, though, it seems too good to be true.

    1. YouTuber Curtis Stone is in B.C. Canada and has been researching using sand as a thermal battery.
      PV heats the sand using excess electricity and stores it for weeks then tubes in the sand carry heat to a blower.
      Joe's issue would probably be cloudiness in MI.....

  12. While I haven't had a geothermal system, I know people who have had it work with good results.
    I'm with the others on power usage - the system my parents had pulled almost 10k in operation and we decided it would be in practical to set up a backup generator; they used a fireplace for backup heat instead.

    The rule of thumb with solar is that the cheapest watt is the one you don't use, to be practical you cut use as much as possible - so anything using a heat pump is off the table, including AC.

    I'd love to be off grid, but haven't found a good solution out here to temps ranging from 120+ to -10 and no trees .. I'm researching underground homes to see what they require.

  13. Almost went the solar route here in Idaho. Did a little more research. Found out it wouldn't power the house in a power outage. Also, Idaho Power pays far less for the power I generate than what I have to pay them. Then the break even point was about the life time of the system. Also, the government incentives were laughable when all this was factored in. Hard pass. Would only consider a stand alone system that I paid for. Too expensive for now.

    1. Imagine what the cost would be if:
      The utility was NOT forced to buy your production
      There were ZERO tax payer funded subsidies involved.

  14. Solar doesn't work when it's covered in snow... just sayin


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