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?
Electric resistive water heater (cumulus)
Needs the grid
One of 7 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
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 you can replace yourself. But every bit of heat is paid for in electricity, so it is the costliest way to heat water.
Build it
This solution is not buildable as a DIY project.
Cost
Low
Upkeep
Occasional
Skill to build
Intermediate
Lifespan
10-15 years; the tank usually fails before the element, and the sacrificial anode governs how long the tank lasts
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Electric resistive water heater (cumulus) (This page) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Intermediate · Upkeep: Light · Change to daily life: None · Works without the grid: No Choose it if you want the cheapest heater to buy, with parts you can replace yourself.
Thermosiphon solar water heater Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Light · Change to daily life: Occasional · Works without the grid: Yes Choose it if you want solar hot water kept in its own insulated tank, with no pump.
Compost-coil water pre-heater Can I use it? Not in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Light · Change to daily life: Occasional · Works without the grid: Yes Choose it if you already keep a big compost heap and want it to pre-heat your water.
Batch solar water heater (integrated collector-storage) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Intermediate · Upkeep: Light · Change to daily life: Daily · Works without the grid: Yes Choose it if you want the simplest solar hot water, panel and tank in one box.
Wood-stove flue water heater (thermosiphon coil) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Intermediate · Upkeep: Light · Change to daily life: Daily · Works without the grid: Yes Choose it if you already run a wood stove and want hot water from it in winter at no extra fuel.
Gas water heater Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Specialist · Upkeep: Light · Change to daily life: None · Works without the grid: No Choose it if you are on the gas mains and want hot water on demand, without keeping a tank hot.
Heat-pump water heater (chauffe-eau thermodynamique) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: High · Skill to build: Specialist · Upkeep: Heavy · Change to daily life: None · Works without the grid: No Choose it if you want electric hot water for a third of the power, and have an unheated room for it.
Sources
ADEME guidance on domestic water heating
Limitations of this page
We don’t list sizing or quantities, as the yield of each technique depends on the quality of its build. The catalogue compares options but doesn’t dimension them. Regulatory notes are indicative, with a French example, and need to be confirmed locally.