Introduction

A Raspberry Pi draws so little power that a small solar panel and battery can keep it running 24/7. This guide covers exactly what you need, how to wire it, and real-world power measurements.

How Much Power Does a Pi Use?

Measured with a USB power meter:

Model	Idle	Light Load	Max
Pi 3B+	1.9W	2.8W	5.1W
Pi 4 (2 GB)	2.7W	3.4W	6.4W
Pi 4 (4 GB)	3.0W	4.1W	7.6W
Pi 5	3.2W	5.0W	12W

For a Pi 4 running Docker services, plan for 4–5W average.

What You Need

Component	Recommendation	Cost
Solar panel	30W (12V) rigid or foldable	~$30
Battery	12V 20Ah LiFePO4	~$60
Charge controller	PWM 10A (e.g., EPever)	~$15
Buck converter	12V → 5V 3A USB-C	~$8
Cables	MC4 connectors, USB-C	~$10

Total: ~$120 for a complete solar Pi setup.

Step 1 — Size Your Battery

The math is simple:

Runtime (hours) = Battery capacity (Wh) / Power draw (W)

A 12V 20Ah battery = 240 Wh.

At 5W average draw: 240 / 5 = 48 hours of runtime without any sun.

With a 30W panel getting 4–5 hours of good sun per day, you generate 120–150 Wh — more than enough to cover the 120 Wh daily draw.

Step 2 — Wire the Solar Panel to the Charge Controller

Connect MC4 cables from the panel to the charge controller's solar input. Polarity matters — red to positive, black to negative.

Step 3 — Connect the Battery

Wire the battery to the charge controller's battery terminals. The controller prevents overcharging and deep discharge.

Step 4 — Add the Buck Converter

The buck converter steps 12V down to 5V USB-C for the Pi. Connect it to the load output of the charge controller (or directly to the battery terminals).

Step 5 — Power On

Plug the USB-C cable into your Pi. It should boot normally.

Choosing LiFePO4 vs Lead-Acid

LiFePO4 (lithium iron phosphate) is the clear winner for off-grid computing:

2000+ charge cycles (vs 300–500 for lead-acid)
Lighter weight
Flat voltage curve (stable power)
Safe chemistry (no thermal runaway risk)
More usable capacity (you can safely use 80–90% vs 50% for lead-acid)

The higher upfront cost pays for itself quickly.

Real-World Test Results

We ran a Pi 4 with Docker (Pi-hole, WireGuard, Nextcloud) on a 20Ah LiFePO4 battery with a 30W panel:

Average draw: 4.8W
Sunny day (6h sun): Battery full by 2pm, stayed at 100% rest of day
Cloudy day (2h sun): Battery dropped to 78%, recovered next day
3 days overcast: Battery dropped to 41%, never shut down

The system ran continuously for the entire 7-day test period.

Tips

Mount the panel facing south (northern hemisphere) at a 30–45° angle
Keep cables short to minimize voltage drop
A small inline fuse (5A) between battery and buck converter is good practice
Monitor battery voltage: 13.4V = full, 12.0V = time to conserve, 10.8V = shut down

Summary

Running a Raspberry Pi on solar is practical, affordable, and surprisingly reliable. With a $120 setup, you get a server that runs indefinitely on sunshine alone.

Tag: solar

Powering a Raspberry Pi with Solar (Beginner Guide)