The architecture
PV charges a 50Ah LFP battery. A fused 12V pump pressurizes the shower line through a strainer and accumulator tank. LEDs and USB can share the bus. For warm water, use a passive black collector/tank or a small DC circulation pump through a solar-thermal panel rather than trying to electrically heat gallons of water from a tiny PV system.
Load and sizing math
The pump runs only while water flows, making daily electrical use surprisingly small.
| Load | Watts | Hours/day | Daily Wh | Notes |
|---|---|---|---|---|
| 12V pressure pump | 70 | 0.5 | 35 | 30 min total shower time |
| LED shower lights | 10 | 2 | 20 | Evening use |
| Circulation pump | 15 | 2 | 30 | Optional solar-thermal loop |
| USB / controls | 5 | 2 | 10 | Timer/sensor margin |
| Illustrative total | 95 Wh/day | Before system margin | ||
Under 100Wh/day is realistic. The 50Ah battery is intentionally generous for cloudy days and pump surge. The 200W array gives fast recovery and spare capacity for a changing-room fan or phone charging.
Full parts list
This is a shopping architecture, not a demand that you buy one exact brand. Match voltage, current and connectors before ordering. Budget ranges reflect the class of hardware rather than a live quote.
200W solar panel kit
Target spec: 2×100W rigid panels or equivalent
More than enough electrical harvest, with room for accessories.
Budget: $100–$260 each
50Ah LiFePO4 battery
Target spec: 12.8V, 50A+ BMS
Handles pump surge and several cloudy days.
Budget: $100–$180 each
12V diaphragm pressure pump
Target spec: 3–5 GPM, 45–55 PSI, pressure switch
Gives real shower pressure from a tank or barrel.
Budget: $60–$140 each
Accumulator tank + strainer
Target spec: Small potable-water accumulator
Reduces pump cycling and smooths flow.
Budget: $35–$90 each
Solar thermal shower collector
Target spec: Black hose/collector mat or glazed DIY collector
Use heat from sunlight directly instead of wasting PV electricity on resistance heat.
Budget: $40–$180 each
12V LED wet-location lights
Target spec: Low-voltage waterproof fixtures
Safe low-voltage lighting for evening showers.
Budget: $20–$70 each
Wiring map
Keep all electrical components outside the wet zone unless explicitly rated for it. The shower head itself needs no electricity.
[200W PV]-->[CONTROLLER]-->[50Ah LFP]-->[FUSED BUS]
| |
15A Pump 3A LEDs
|
Tank-->Strainer-->Pump-->Accumulator-->Mixer-->Shower
Solar-thermal preheat loop ---^
Step-by-step build
Choose water source and drainage
Decide whether the shower draws from a rain barrel, tote, cistern or pressurized source, and provide legal/sensible gray-water drainage.
Build the shower structure
Finish posts, privacy walls and roof/collector supports before plumbing or wiring.
Mount the thermal collector
Put the heat collector in full sun and include a mixing valve so hot stagnation temperatures cannot reach the shower directly.
Install the pump train
Tank outlet → strainer → pump → accumulator → plumbing. Add service unions so the pump can be replaced without cutting pipe.
Install the solar electrical box
Mount controller, fuse block and battery in a dry service compartment.
Wire pump and lights
Use a dedicated pump fuse and waterproof switch. Keep low-voltage lighting connections in rated junctions.
Prime and pressure-test
Run cold water first, check fittings, cycle the pump and adjust accumulator pressure if required.
Commission hot-water mixing
Heat the collector, then verify the mixing valve prevents scalding at maximum solar temperature.
Commission it before you trust it
The project is not finished when the LED comes on. Run it through a controlled test so the first real failure is not in the field.
- Drainage complete
- Pump strainer accessible
- Pump branch fused
- Wet-zone electrical separation verified
- Mixing valve tested hot
- Accumulator cycling normal
- Battery secured
- Panel wind-fastened
- Winter drain procedure documented
Mistakes to avoid
Undersizing the battery because the panel is large
Panels make energy only when conditions cooperate. The battery has to carry the load through night, cloud and short high-demand events. Size energy storage from watt-hours, not panel watts.
Ignoring standby loads
Controllers, routers, cameras, inverters and cellular hardware can consume power 24/7. On small projects, a 5W always-on device is 120Wh per day—sometimes more than the 'main' load.
Using one fuse for the entire project
Fuse each branch according to its conductor and load. The fuse protects wire, not the gadget. A downstream short should not require an oversized main fuse to clear.
Mounting the panel where the project is instead of where the sun is
The load can sit in shade. The panel cannot. Use a cable run, pole or remote mount to put the collector in the best solar window.
Skipping a low-voltage disconnect
Deep-discharge protection is cheap insurance. Many charge controllers or smart battery systems can disconnect noncritical loads before the battery is abused.
Upgrade path
Add a float switch
Protect the pump from running dry when the tank gets low.
Add an occupancy timer
Automatically shut lighting and circulation after a set time.
Add a larger tank and collector
For cabin use, more water storage and thermal collector area improves consistency without increasing battery size.
Frequently asked questions
Can solar panels heat the shower water electrically?
They can, but for a small off-grid build solar-thermal heating is far more efficient and cheaper.
Can I use a 20Ah battery?
Yes in sunny seasonal use; 50Ah adds surge and cloudy-day reserve.
Does the pump need an inverter?
No. Use a native 12V pressure pump.
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