A simple solar well pump system: no inverter, almost no battery, just water where it is needed

This past weekend I installed a very simple solar-powered water system at a friend’s house. Until now, it was normal for her to pull 15 buckets of water every day from a 59-foot well, using only a rope. She also has back problems from an old injury, so the real objective of this project was very clear: She should never have to pull water by hand from that well again.

Not “build a perfect solar system.”
Not “install a big off-grid power plant.”
Not “buy an expensive kit.”

Just this: water should come out of the well by itself. And now it does.

Before explaining the system, I want to point out a few mistakes I often see when people start using solar power for simple rural tasks:

- Using panels that are too small. People often calculate the exact theoretical wattage they need and then buy a tiny panel. But real life is not a catalogue. Clouds, angle, dirt, cable losses, startup current, winter sun… all of that exists.
- Adding an inverter when DC would do the job. Many pumps, lights, USB chargers, routers, fans, and small tools can work directly from 12V or 24V DC. Turning solar DC into AC, only to turn it back into DC inside a device, is often just expensive theatre.
- Buying too much battery. Batteries are useful when you need electricity at night or when you need to store energy for later. A fridge, a washing machine, or evening lighting may justify batteries. But water is different.

Do I need to pump water at night? No!. So in this case, the “battery” is not a lithium battery. It is a 500-liter water tank. If what I consume is water, why not store water? That is cheaper, simpler, safer, and easier to understand.

The panel

I did not use a small “12V battery charging panel.”

Here in Europe, a theoretical 200W panel sold for small battery systems can easily cost around 350€. But large panels used for house or industrial installations are much cheaper per watt. I found a large panel of around 650W for 92€.

It works at a higher DC voltage, in the 40–50V range depending on conditions, which is perfect for reducing cable losses and getting useful production even with less-than-perfect sun.

So the logic was simple:

more power,
lower cost,
better performance in weak light,
no need to push the panel close to its limit.

That is a good deal. Sometimes the boring industrial option is the clever permaculture option.

The battery: a tank, not a battery bank

This system does not need to pump water at night.

During the day, the panel runs the pump and fills a 500-liter tank. That gives enough water for several days of basic use: washing, the sink, and the bathroom.

So instead of buying a large battery bank, I used the cheapest and most appropriate storage system for this task:

a water tank.

This is important. When designing an off-grid system, first ask:

What am I really trying to store?

If the answer is electricity, use a battery.
If the answer is cold, maybe use insulation.
If the answer is water, use a tank.

The regulator: DC-DC converter instead of inverter

The pump is a 12V DC pump of about 100W.

So I did not need an AC inverter.

Instead, I used a DC-DC converter, similar in concept to what is used in camper vans and vehicles. These devices take one DC voltage and convert it into another stable DC voltage.

In this case, the converter accepts a solar input between 30V and 96V DC and provides a stable 12V DC output, rated at 15A.

That means:

12V × 15A = 180W

The pump is around 100W, so the converter is oversized enough to deal better with motor startup current. Small motors often draw more current when starting than when running, so designing only for the nominal wattage is a good way to be disappointed.

A battery charge controller would not have been the right tool here. Charge controllers are designed mainly to charge batteries. In this system, I wanted to power a 12V DC load directly from a larger solar panel.

So the chain is:

solar panel → DC-DC converter → 12V pump

Simple.

The water pump

The pump is a small 12V DC water pump, rated for the lift I needed.

It does not have a huge flow rate, and that is fine. This is not an irrigation system that needs a high flow in a short time. It only needs to fill a tank slowly during the day while the sun is available.

That changes everything.

A slow pump running for several hours is often better than a powerful pump that needs a big inverter, large batteries, and thicker cables.

The question is not:

How fast can I pump?

The question is:

Can I fill the tank during the day?

In this case, yes.

Extra: USB charging

I also installed a small USB charger with a voltmeter, the kind sold for cars and camper vans.

This lets my friend charge her phone and other small devices during the day. She already uses motion-sensor lights with internal batteries for nighttime lighting, so now those can also be charged from the same solar setup.

That was not the main goal, but it is a useful bonus.

Basic layout

The system is very simple:

Large solar panel on the roof
Cable from the panel to the DC-DC converter
12V output from the converter
One output to a USB charger
One output through a switch to the pump
Pump fills the water tank during the day

I also reused an old switch from an electrical box that was already in the shed. It now looks like a proper fused switch panel, which made me smile. Reusing old material is not always elegant, but sometimes it has character.

The result is very simple: a home that now has water without daily physical effort, without an inverter, without a large battery bank, and without buying one of the expensive ready-made kits. This little project made me feel very good. It is a small system, but it solved a real problem. A person who used to pull bucket after bucket from a deep well now turns on a switch and water comes out. That is appropriate technology.

Care for the earth: solar power, low waste, simple design.
Care for people: less pain, less daily burden, more dignity.
Return of surplus: using knowledge and work to make someone’s life easier.

And perhaps the most amazing part: It works!!!.