We can heat our well insulated 900sqft of living space to 65-70°f using around 2 cords of wood each year with our Rocket Mass Heater. We typically wake up to 65°f and burn a fire in the morning and another fire in the evening. A "J" tube burn chamber covered by a 55gal barrel creates radiant heat as well as a thermal pump which forces exhaust gasses horizontally though ducting in a large box filled with pea gravel. The gravel extracts most of the heat from the exhaust radiating it out slowly after the fire burns out. By the time the exhaust reaches the chimney it's 120-200°f down from 300-500°f at the barrel. The combustion is nearly total so very little smoke is exhausted and maximum BTUs are used to heat the space. Built with materials found at most big box hardware stores Rocket Mass Heaters are cheap to build, easy to source, and incredibly efficient. It is the favorite contraption I've built on the homestead.

Here's a note I wrote about our Rocket mass heater a few years ago to provide some more details on how amazing these heaters are:

Now that transaction fee storm has passed I'm back to heating my living space primarily with wood in a rocket mass heater instead of Asics.

Wood is burned in the small firebox and heat radiates from the barrel warming the space quickly while the fire burns.
https://i.nostr.build/2xaq.jpg
As the exhaust gasses make their way to the chimney, they pass through ductwork in a plywood box filled with pea gravel.

The majority of the heat from the exhaust is transfered to the gravel before exiting up the chimney. By the time the gases exit the box, they are cool enough for me to put my hand on the chimney pipe.

After the fire burns out, the heat absorbed by the pea gravel slowly radiates out into the living space until the next fire is burned and the gravel is recharged with heat once again. I built this rocket mass heater for a fraction of the cost of a wood burning insert, with no special tools, materials, or skills.

It has been an unusually warm November and December here at the homestead. Normally we have to start burning wood in the rocket mass heater early November to stay comfortable but this year, the bitcoin mining dehydrator was enough to stay warm and do some food preservation simultaneously.


Transaction fees started climbing and I was shocked to see the most efficient miner I had approaching break even at my electric rate.


I didn't have the circuit to run it wired yet but this bump in fees was the motivation I needed to get the miner hashing. Coincidentally, the weather also started to get colder finally so getting the miner up and running was a win/win.

It successfully kept us and our guests warm through the holidays, even earning some Bitcoin beyond the cost of power at times, all while allowing us to save our firewood.

We did have to fire up the rocket mass heater a handful of times, but so far we've burned less than half the amount of wood compared to previous years. This is thanks to the combination of the warm weather, and high transaction fees allowing us to stay warm with heavily subsidized electric heat.

This might be the first winter we make it through with wood leftover for the next year, typically I'm scrounging for the last couple weeks.