If your tiny home is off-grid, the toilet is where a lot of builds get expensive fast. A septic system means digging, permits and a big check. A composting toilet skips most of that: no water, no tank in the ground, and a fan that sips a few watts from your solar.
Here’s how they actually work, what they cost, the honest downsides, and which models people living in tiny homes keep buying.
How a composting toilet works (the 30-second version)
Almost every modern composting toilet does three things:
- Separates liquids from solids. Urine goes to a front bottle or a drain line. Solids drop into a rear bin. Keeping them apart is what stops the smell.
- Dries the solids. The bin is mixed with a dry material like coconut coir or peat moss, usually by turning a handle.
- Vents the air outside. A small fan pulls air out through a vent hose, so the bathroom stays fresh.
No water, no flush, no plumbing to a septic tank. That’s the whole trick.
What a composting toilet costs
The popular self-contained models run about $1,000. Budget, no-power options start around $350. (Prices from Mortons on the Move’s comparison; prices move, so check the current number before you buy.)
| Model | Approx. price | Power | Solids emptied (1–2 people) |
|---|---|---|---|
| Nature’s Head | ~$1,030 | 12V fan | Every 4–6 weeks |
| Air Head | ~$1,100 | 12V fan | Every 2–4 weeks |
| Separett Villa | ~$1,000 | 12V or 120V fan | Every 3–4 weeks |
| OGO Origin | ~$985 | 12V fan + agitator | About every 2 weeks |
| Trelino | $350–$550 | None | Frequently |
Compare that to a conventional septic system, which usually runs into the thousands once you add excavation, the tank, the drain field and the permit. For a lot of off-grid tiny homes, the composting toilet is the single biggest money-saver in the whole utilities budget. Run your own numbers in the off-grid build budget calculator.
The best composting toilets for a tiny house
Nature’s Head: the one most tiny home owners buy
It’s the default pick for a reason. Compact enough for a tiny bathroom, a quiet 12V fan, and for one or two people the solids bin typically goes 4–6 weeks between emptying. The liquids bottle is about 2.2 gallons and needs dumping every few days.
Check the current price of Nature’s Head on Amazon
Separett Villa: if you want a “normal” toilet feel
It looks closer to a regular toilet and can drain the urine straight to a line instead of a bottle you carry out. That makes it a strong pick for a full-time tiny home where you can run that drain. It runs on 12V or 120V.
Check the current price of the Separett Villa on Amazon
Air Head: the Nature’s Head rival
Very similar design and price. Some owners prefer its build quality and parts support. Expect to empty solids every 2–4 weeks.
Check the current price of Air Head on Amazon
Trelino: the budget, no-power option
No fan, no wiring, a fraction of the price. The trade-off is more frequent emptying. Good for a cabin, a weekend place, or a backup while you build.
Check the current price of Trelino on Amazon
How much power does it use?
Very little. Most models run a small 12V fan around the clock, which is a tiny slice of a solar budget compared to a fridge or a well pump. If you’re sizing your system, add the fan to your daily load and see where you land in How Many Solar Panels Does a Tiny Home Need?
The honest downsides
- You empty it yourself. Urine every few days, solids every few weeks. It’s not gross if it’s working right, but it is a chore.
- You need a vent. Plan a hole in the wall or roof for the vent hose before you finish the bathroom.
- Your greywater still has to go somewhere. A composting toilet only handles the toilet. Your shower and sink water is a separate system.
- Rules vary by county. Some places treat a composting toilet as fine, some still require a septic system for the house to pass inspection. Check before you build.
New Mexico note
If you’re building in New Mexico, the state allows up to 250 gallons a day of residential greywater (shower, bathroom sink, laundry, not the kitchen sink) to be reused for landscape irrigation without a permit, as long as you follow the conditions, like keeping it on your own property and away from wells (NMED graywater rules). That pairs well with a composting toilet. For the toilet itself, confirm with NMED’s Liquid Waste Program or your county before you skip septic.
Is a composting toilet right for your tiny home?
It’s a strong fit if you’re off-grid, short on water, or trying to avoid a septic bill. It’s a weaker fit if your county requires septic anyway, or if nobody in the house will handle the emptying.
The toilet is one of six utility systems every off-grid tiny home needs. See the full list in the Off-Grid Tiny Home Utilities Checklist, and see where it fits in the total budget in What an Off-Grid Tiny Home Actually Costs.
Planning an off-grid tiny home? Get the free Off-Grid Planning Pack: the utilities checklist plus a budget planner, so you don’t miss a system.
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