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Is it Possible to Heat Your Home for Free? Almost.


I heat most of my home with a pellet stove insert.


The house feels much warmer with a pellet stove than with a traditional furnace.  It also made the living room a great place to hang out in the winter months (as my son, home from school, is doing right now).

However, it takes a bit of work to keep it fed and clean, much less than a traditional wood stove and more than a gas furnace.

Another big benefit is that it’s inexpensive to operate.  All told, it costs me about $750 a year to heat my relatively large home.  That’s a big savings over what it would cost me to do it with natural gas. It’s a massive savings over what it would cost me with oil or electricity.

As good as this is, my job is to figure out if it’s possible to produce more and get more resilient in the process.

In particular, is it possible to produce electricity with wood pellets too?


One way to do that would be to use a micro combined-heat-power (CHP) furnace.

Micro CHP furnaces produce both heat and electricity.

NOTE:   CHPs work on the simple principle that 80% of the energy the power company uses to produce electricity is usually lost as heat.  So, if you produce this electricity where you use it, it’s possible to use heat that would otherwise be lost, to heat your home and your hot water.

Here’s how it would work.  I would install a micro CHP like a furnace.  Like any furnace or pellet stove, it would turn on whenever I needed heat.  The only difference would be that it would also generate electricity when it does turn on.  The first 20% of the energy produced to heat my house would be used to produce electricity instead.

In concept, this would be a pretty amazing system.  The costs of fueling the system with pellets would be largely offset by electricity it produces.

Unfortunately, there isn’t a MCHP out there that burns wood pellets yet.  There was one, from a German start-up called SunMachine (it used a Stirling engine).

SunMachine pellet2



It didn’t last long.  SunMachine never made it out of the start-up phase.  It went bankrupt a couple of years ago before it was able to ship product.

Fortunately, there are other options for producing electricity locally.






PS:   A sign of things to come.  California’s utilities are asking for a fee increase of $1.3 billion.   The reason?  Many of their customers are installing solar panels.  As a result, these customers buy less electricity from the grid.  To maintain the grid, the utility has to jack up prices for the people still dependent on it.  We’re going to see this dynamic everywhere in the global industrial system in the next decades.   As people eliminate their dependence on these systems by becoming producers, the folks that are too lazy to leave are going to be left holding the tab….

PPS:  If you are interested in the Tech specs for the SunMachine CHP, here they are:

Datasheet Sunmachine-Pellet
1.0 CHP unit
Electric power fed to grid: —— approx. 3 kW (electric output)
Thermal power: approx. ——- 10.5 kW (thermal output)
Efficiency (electric): ———— approx. 20 %
Overall efficiency: ————– approx. 90 %
CHP coefficient: —————- 0.286
Flow temperature: ————- 50 – max.75° C / 122 – max.162° F
Return temperature, max. —– 60° C / 140° F
optimal return temperature: — 30° C / 86° F
Sound emission: ————— approx. 49 dB
Color: ————————- RAL 5001 (blue-green)
Weight: (without covering): — approx. 410 kg / approx. 903.89 lbs
Dimensions LxWxH in mm / inch: 1160x760x1590 / 45.7″x30″x62.6″
1.1 Burner unit
Fuel: woodpellets, DIN plus (german industrial standard)
Power: 14.9 kW fuel provided
Maintenance interval: recommended once a year or every 3,500 operating hours
1.2 Stirling engine
Cylinders: 1
Cylinder capacity: 520 ccm / 31.73 cubic inch
Speed range: 500 – 1,000 rpm
Working gas: nitrogen
Working pressure: max. 40 bar / max. 580 PSI
2.0 Input with inverter
Feed to grid: single phase 230 Volt 50 Hz
Grid control: 3 phases through build-in grid disconnecting device
2.1 Inverter
Nominal output: 3.4 kW
Peak capacity: 3.8 kW
Input voltage: 350 – 750 Volt
Efficiency: max. 95.7 %
Power factor cosPhi: 0.997
3.0 Control Unit
Interface: graphic touchscreen display
Interface RS 232: suitable for modem and PC (readout of important data)
Optional: 3 heating circuits and one warm water controllable,
switching output for peak load demand
4.0 Feed
Pellet-supply-container: approx. 50 l / approx. 13.2 US gallons
Pellet feed from storage room / bag – silo / via vacuum delivery with internal day / night control
subterranean tank to sunmachine: (closed system)
5.0 Exhaust
Exhaust: Exhaust gas routing after request with solid fuel boilers condensate
6.0 Recommended heat-store stratified storage: min. 1,000 liters / 264 US gallons incl. heating rod 9 kW


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Comments on this entry are closed.

  • Jim Dauster

    And once someone gets that down, the next step would be converting the stove into a gasifier, so you produce biochar as a byproduct. I guess the trick would be figuring how to automate the stove to dump the charcoal before it turns to ash.

  • Steve Dune

    This will be great if my house will be warm without using any of the HVAC product and for free that will be great.Thank you for this information..

  • The theory sounds good, but in practice there may be problems… Complexity is one issue since the parts are probably quite precise and the system is not something a local repairman is familiar with. Fueling it is another if consistent and uniform wood pellets become scarce.

    I have read about a variety of Natural Gas units. Internal combustion types would be more familiar to a local mechanic, and bio-gas could perhaps substitute for the natural gas someday.

    Here is an article from someone who has a NG CHP unit in a New England home:
    His conclusion seems to be that if your home is in a cold climate and has poor insulation, it is probably worthwhile.

    I think it may be better to improve the insulation of individual homes and save these CHP units for places that can use the heat and power all year (like maybe a community laundry or kitchen or manufacturing workshop…)

  • Heating with wood pellets is super efficient, but I’ve steered away from them to stay with a regular wood burning firestove since pellets require you to either own the pellet making machine or be dependent upon someone else to purchase the pellets from (either option requires energy to operate).

    • John Robb

      Scott, that’s changing. Pellet making is now a great local business opportunity for handy entrepreneurs (either in coop form or standard sole proprietorship). Wrote up a full analysis of how to pull that off in November’s Resilient Strategy report. Lots of advantages to pellets (you can use grass, leaves, etc.). JR

  • Great post. Any thoughts on how to provide heat in an apartment that does not have a fireplace in case the “grid” goes down? Thanks John

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