Tankless vs Tank RV Water Heaters: Which Actually Wins for RV Use
On-demand tankless sounds ideal, but tank heaters still have advantages for RV-specific use cases. Here's the honest comparison.
RV manufacturers have shifted heavily toward tankless (on-demand) water heaters in recent years. The marketing sells simplicity and unlimited hot water. Reality is more nuanced — tank heaters still win on several dimensions important to RV use.
How Each Works
Tank heater
Traditional design. A 6- or 10-gallon tank holds water heated by a propane burner (and often an electric element as backup). Water sits at temperature; when you turn a faucet, hot water flows immediately. Recovery: burner reheats after use.
Tankless heater
On-demand design. No tank. Cold water flows through a heat exchanger where it's heated by a propane burner (or occasionally electric) as it passes through. Hot water is available continuously as long as flow is maintained.
The Comparison
| Tank | Tankless | |
|---|---|---|
| Hot water duration | Limited (10–15 min) | Continuous (unlimited) |
| Warmup time | None (always warm) | 10–20 seconds per use |
| Space in rig | Larger | Smaller |
| Cost | Lower | Higher |
| Propane efficiency (heavy use) | Lower | Higher |
| Propane efficiency (light use) | Higher | Lower (each use ignites) |
| Freeze tolerance | Higher (drainable) | Lower (heat exchanger vulnerable) |
| Electric backup on shore power | Common | Rare (high draw) |
| Simplicity/reliability | Higher | More electronics, more failure points |
Where Tank Wins
Occasional handwashing and brief use
Tankless heaters ignite each time flow starts. Brief handwashing barely heats water before you turn off the faucet — propane is consumed for near-zero hot water output. Tank heaters have water ready without ignition cost.
Cold-weather camping
Tank heaters can be drained for winter and don't crack from freezing. Tankless heat exchangers hold residual water in fine passages that freeze and split — repair is expensive.
Electric shore power use
Most tank heaters include an electric element that runs on shore power, saving propane during hookup stays. Tankless typically requires propane for every use regardless of hookup.
Reliability
Tank heaters are simpler mechanically. Fewer electronic controls, no flow sensor requirements, no modulating burner. Tank heaters can be repaired with basic tools; tankless failures often require factory service.
Lower cost
Tank heaters cost less to buy and install. Replacement units run about half the price of comparable tankless units.
Where Tankless Wins
Long showers or multiple back-to-back showers
The killer app. A family with three kids taking sequential showers exhausts a 6-gallon tank quickly. Tankless never runs out.
Continuous flow uses
Dishwashing after a big meal, filling a soaking tub, guests washing multiple pots. Continuous flow requirements favor tankless.
Space savings
Tankless units are compact, freeing storage or wall space. Meaningful in smaller trailers where every cubic foot matters.
Propane efficiency in heavy use
Tankless heats only what you use, without standby losses. For heavy-use scenarios (family showers daily), tankless burns less propane over time despite the per-use ignition penalty.
Retrofit Considerations
Replacing a tank heater with tankless in an existing rig involves:
- Different mounting footprint — cutting or modification usually required.
- New propane line sizing (tankless burners have higher peak BTU).
- New 12V wiring for control board.
- Water line reconfiguration.
- Winterization procedure changes.
Retrofit typically runs shop labor in the 4–8 hour range plus the unit cost. Not a trivial project. Most retrofits happen when the original tank heater fails and replacement is the natural decision point.
The Honest Recommendation
Small trailer used occasionally, single or couple, weekend camping: tank heater remains a reasonable choice. Simple, cheaper, more freeze-tolerant.
Family rig with multiple showers, full-time use, hot climate: tankless earns its price. Unlimited hot water changes daily life for families with kids.
Winter-heavy use in cold climates: tank heater's freeze tolerance is a real advantage.
Bottom Line
Tankless isn't universally better. It's better for specific use cases (heavy continuous use, families, hot climates) and worse for others (light use, cold climates, budget-conscious owners). Match to your actual use pattern rather than following the marketing default.
Frequently Asked Questions
Is a tankless RV water heater always better?
No. Tankless heaters win on continuous hot water and space savings but lose on propane efficiency at low flow rates, freeze tolerance, and cost. Tank heaters remain the right choice for many RV use cases despite the marketing hype around tankless.
How much hot water does a 6-gallon RV tank heater give?
Roughly 10–12 minutes of steady shower use before running out — the tank provides its full contents plus continuous heating during use. A 10-gallon tank stretches to 15–18 minutes. Recovery to full temperature takes 20–30 minutes on propane.
Can tankless heaters run on 30-amp shore power?
Yes, but propane-fired tankless is more common for RVs. Electric tankless heaters draw significant current (30–50A) and typically aren't practical for 30-amp shore power. Most RV tankless installations are propane with a small ignition draw.
Are tankless heaters more expensive to operate?
Complicated answer. Per gallon of hot water: tankless is usually more efficient. But tankless heaters cycle on and off with each faucet use, consuming propane for ignition and startup — inefficient for brief hot water needs like handwashing. Net efficiency depends heavily on usage pattern.
Do tankless heaters freeze more easily?
Yes. Tankless heat exchangers are much more vulnerable to freeze damage than tank heaters. A tank heater with drained water tolerates freezing; a tankless heat exchanger holds residual water in fine passages that freeze and crack. Winter storage of a tankless requires more careful winterization.