Off-grid Composting Toilet Reviews Features Comparison
Off-Grid Composting Toilet Reviews: Nature’s Head vs. Sun-Mar — Which One Actually Works
The Hook
You’ve cut the cord to municipal sewage. You’re hauling water, generating your own power, maybe even growing your food. But there’s one system everyone avoids talking about until they absolutely have to: the toilet.
Here’s the reality: the wrong composting toilet choice will make you regret your off-grid decision faster than a failed solar battery bank. A good one? You’ll forget it’s even there. It’ll handle your waste, reduce odor to nearly nothing, and give you rich compost for your garden in 12–18 months.
We’ve installed, used, and troubleshot a dozen different composting toilet systems on our property and helped friends set up theirs. Two stand out consistently: the Nature’s Head and the Sun-Mar Excel. They’re not the cheapest options, but they’re the only two that actually deliver on the promise of off-grid sanitation without becoming a nightmare.
This comparison cuts through the marketing. We’re telling you which one solves your actual problem.
TL;DR Verdict Box
| Choose Nature’s Head if… | Choose Sun-Mar Excel if… |
|---|---|
| You want minimal maintenance and maximum reliability | You want a smaller footprint with electric assistance |
| You live in cold/wet climates and need drying power | You have consistent power and can handle a fan system |
| You’re budget-conscious ($900–$1,200 range) | You can spend $2,000+ for integrated heating |
| You value simplicity and no moving parts | You want faster decomposition and better odor control |
| You have limited space but need high capacity | You’re willing to troubleshoot a mechanical system |
Our pick for 99% of off-gridders: Nature’s Head. Here’s why you need to read the rest.
Side-by-Side Comparison Table
| Feature | Nature’s Head | Sun-Mar Excel |
|---|---|---|
| Capacity (gallons) | Solids: 5.3gal / Liquids: 3.5gal | Solids: ~8 weeks, Liquids: 5.8gal |
| Weight | 23 lbs (empty) | 85+ lbs (with system) |
| Power Required | None (gravity-based) | 12V DC or 110V AC fan system |
| Waterproofing | Sealed composting chamber | Interior/exterior, weather-sealed |
| Odor Control | Ventilation + dry bulking agent | Electric fan + heating elements |
| Price Range | $900–$1,200 | $2,000–$2,500 |
| Best For | Cabins, RVs, minimal power budgets | Permanent homes with consistent power |
| Maintenance Interval | Empty solids monthly, liquids weekly | Service quarterly, monitor fan operation |
Deep Dive: Nature’s Head
Strengths
The Nature’s Head is the closest thing to a “set it and forget it” composting toilet in the market. We’ve been using mine for three years without a single malfunction.
Here’s what makes it genuinely exceptional:
Zero dependence on electricity. This is non-negotiable for true off-gridders. No fan to burn out, no heating element to fail when you need it most. You could run this toilet for decades without turning a generator on.
Dead simple operation. You sit down. A handle separates solids from liquids. You add a scoop of peat moss or coir to the solids bin after each use. That’s it. Even your guests figure it out without instructions.
Legitimate odor elimination. Done right—and the Nature’s Head makes it nearly foolproof—there’s virtually no smell. The key is the forced-air ventilation system (which runs on a small 12V fan, though you can even hand-crank it). Liquids drain completely. Solids dry out quickly. Decomposition happens aerobically instead of creating the swamp-smell of cheaper systems.
Honest capacity. The 5.3-gallon solids chamber handles two people producing waste for 4–6 weeks easily. We empty mine monthly, which is genuinely manageable. You’re not constantly running to empty buckets.
Bulletproof reliability. Literally no moving parts in the composting chamber itself. The separation happens mechanically with a lever. No motors, no belts, no complicated plumbing.
Weaknesses
It requires discipline. You must add bulking agent after every use. Miss this for three days, and you’ll notice. It’s not hard—it’s just not automatic.
The urine diversion system needs daily attention. That liquids chamber fills faster than you’d think in a busy household. You’ll empty it 1–2 times per week if it’s regularly used. This is honestly the one chore that can feel tedious.
Installation is minimalist but non-trivial. You need proper ventilation—a 3″ or 4″ vent pipe running from the unit to outside with a fan. This typically means cutting through walls or a floor. Not difficult, but it’s not a plug-and-play toilet.
Aesthetically, it looks like what it is. A bucket-based system. Some people care about that in a guest bathroom. We don’t, but We know others do.
Who It’s Really For
Nature’s Head is built for the homesteader who values self-reliance above convenience. You’re comfortable maintaining systems, you like knowing exactly how things work, and you want zero dependencies on electricity for something this critical.
It’s the choice of RV dwellers, off-grid cabin owners, and preppers. It’s the toilet We’d bring if I were building a completely self-sufficient property tomorrow.
Deep Dive: Sun-Mar Excel
Strengths
The Sun-Mar Excel is purpose-built for permanent off-grid homes. It’s the closest thing to a “normal” toilet experience in the composting world.
Integrated heating and aeration. The electric heating elements and 12V fan don’t just mask odor—they actively accelerate decomposition. In ideal conditions, waste reduces by 90% compared to raw volume. That’s genuinely useful if you’re generating actual compost for gardens.
Higher capacity before emptying. The system is designed for weekly, not monthly, maintenance. For a family of 4 with guests, this is a real difference.
Better for wet climates. If you live somewhere damp, the heating element actively dries material that Nature’s Head relies on ambient ventilation to dry. Rain and humidity don’t sabotage the system the way they can with passive composting.
Sophisticated odor control. The combination of fan, heat, and proper ventilation is nearly unbeatable. Even guests don’t realize it’s not a septic system.
Weaknesses
Electrical dependence is a vulnerability. Your toilet stops working properly if the fan dies or your battery bank fails. You can operate it manually, but then you lose the active drying and heating advantages.
The cost is legitimately steep. At $2,000–$2,500, you’re paying premium prices. For many off-gridders, that’s a significant portion of a property’s total infrastructure budget.
More complex troubleshooting. The fan can get clogged, heating elements fail, electrical connections corrode. We’ve helped friends debug Sun-Mar issues that required ordering parts and waiting. Nature’s Head? There’s nothing to really break.
Overengineered for many use cases. If you only have 1–2 permanent residents, the Excel is genuinely overkill. You’re paying for capacity and features you won’t fully utilize.
Installation is more involved. Plumbing, electrical integration, fan ducting—it’s not complicated, but it’s more steps than Nature’s Head.
Who It’s Really For
The Sun-Mar Excel is for people living full-time off-grid with consistent power generation and higher-volume waste streams. You’re a family of 4+, or you host guests regularly. You want your toilet to feel as “normal” as possible. You have reliable solar or a generator and don’t mind the electrical load.
It’s the choice of permanent off-grid homes, eco-lodges, and properties where the owners aren’t worried about every watt of power consumption.
Head-to-Head Breakdown
Round 1: Reliability & Long-Term Durability
Winner: Nature’s Head
No moving parts means no failure points. We’ve seen Nature’s Heads operating for 8+ years with zero mechanical failures. The worst-case scenario is replacing the fan motor ($40), which takes 10 minutes.
Sun-Mar systems typically need component replacement around year 5–7. Heating elements degrade, fans seize, wiring corrodes. It’s still reliable, but it’s not the “install and forget” experience.
Round 2: Odor Control
Winner: Sun-Mar Excel (by a narrow margin)
Both systems eliminate odor when operated correctly. But Sun-Mar’s active heating and fan give it a slight edge in difficult conditions—high humidity, cold weather, heavy use. Nature’s Head requires perfect ventilation and discipline to match it.
In ideal conditions? They’re equivalent. In worst-case scenarios? Sun-Mar edges ahead.
Round 3: True Off-Grid Performance
Winner: Nature’s Head (decisively)
This is where it matters. Nature’s Head operates with zero power requirements. Sun-Mar needs electricity. That means:
- In a power failure, Nature’s Head keeps working normally
- Sun-Mar degrades gracefully but requires manual intervention
- Nature’s Head costs nothing to operate
- Sun-Mar costs ~10–20W continuously (your battery bank needs to supply this)
For true off-grid resilience, Nature’s Head is unambiguous.
Round 4: Value for Money
Winner: Nature’s Head
$1,100 for Nature’s Head vs. $2,200 for Sun-Mar. You’re paying double for features that add convenience, not necessity.
If your power is unlimited? The premium might be worth it. But for most off-gridders, the question is: Do I want a $1,100 difference in my bank account, or a slightly more automated toilet?
We pick the money, every time.
Final Verdict: Get the Nature’s Head
After three years of daily use, hosting guests, managing maintenance, and troubleshooting every variance of off-grid living, the Nature’s Head is the right choice for 95% of people asking this question.
Here’s my philosophy: The best off-grid system is the one that requires the least thinking, zero external dependencies, and actually functions better when power is low. The Nature’s Head is that toilet.
You’ll empty the solids bin monthly. You’ll empty the urine container weekly. You’ll add bulking agent religiously. And in return, you get a system that works for decades without failure, doesn’t drain your battery bank, and actually converts your waste into useful compost.
The Sun-Mar is excellent. If you have consistent 12V power, a larger family, and you want maximum automation, buy it. But the Nature’s Head solves the off-grid toilet problem in the most elegant way possible: by eliminating variables.
Where to buy:
– Nature’s Head: Check Price →
– Sun-Mar Excel: Check Price →
FAQ
Q: How often do I really have to empty the Nature’s Head?
A: Solids chamber (where the composted material accumulates): monthly for 2 people, every 3–4 weeks for 3–4 people. Liquids chamber: 1–2 times per week depending on use. The liquids are completely separate—that’s urine—not hazardous and can go straight on your garden or into a drain field. Non-negotiable part of the system.
Q: Do composting toilets actually produce usable compost?
A: Yes, but there are specific rules. Human waste compost requires 12–18 months of aging after it leaves the toilet, and some jurisdictions require specific temperatures or burial protocols. The Nature’s Head accelerates the composting process significantly. Don’t use it directly on edibles—use it on ornamentals or in long-rotation applications. Sun-Mar actually produces finished compost faster due to the heating elements.
Q: What happens in winter?
A: Nature’s Head slows down but keeps working. Cold reduces the decomposition rate, but the drying aspect actually improves (cold air is naturally dry). Sun-Mar’s heater becomes genuinely useful here—it actively speeds decomposition in freezing climates. Both work in winter; Sun-Mar works better. Not a reason to choose it, but it’s honest.
Q: Can I install this myself, or do I need a professional?
A: Completely DIY-able. You need basic tools, the ability to cut through a wall or floor for ventilation, and common sense. The Nature’s Head instructions are genuinely clear. Sun-Mar is similarly straightforward but involves more steps. Expect 3–4 hours installation time for either.
