Lowtech Graph lists low-tech options for every need of a home. Here you can compare them, find tutorials to build them, and link them together into a circular system. Why low-tech?
Domestic water heating
Heating the part of the water that is used hot: showers, washing up, laundry. It is usually the second-largest energy use in a house after space heating. The options differ in what provides the heat, whether it is available on a grey day, and how much of the demand it covers without bought energy.
Ranked by how much of the hot-water demand is met without purchased energy. Solar thermosiphon leads because it collects and stores with no pump; the batch heater collects as freely but loses more overnight because the store is the collector. Flue and compost coils are free but only while the stove burns or the pile is hot, and the compost coil pre-heats rather than reaching final temperature. An electric or heat-pump heater is the most dependable and the only one where every unit of heat is bought.
Solutions
Thermosiphon solar water heater: A solar panel for water, with a storage tank placed higher than the panel. The sun heats water in the panel; warm water rises on its own into the tank and coole
Compost-coil water pre-heater: A coil of pipe buried in an active compost heap, with water passing through it on the way to the water heater. The heap stays warm as it breaks down and warms t
Electric resistive water heater (cumulus): An insulated tank of water with an electric heating element inside, like a large kettle. It is cheap to buy and simple: a failed element or thermostat is a part
Wood-stove flue water heater (thermosiphon coil): A copper coil wrapped around the flue of a wood stove, linked to a water tank. The hot flue heats the water, which rises to the tank on its own. It gives hot wa
Gas water heater: Heats domestic hot water by burning gas, either on demand as the tap runs or into a stored cylinder. On-demand avoids keeping a tank hot for nothing; a cylinder
Heat-pump water heater (chauffe-eau thermodynamique): A water heater with a small heat pump on top of the tank. It takes warmth from the surrounding air and moves it into the water, giving two to three and a half t