Positive word describing something that is not high-tech?

The company where I work has developed a product that is very easy to use and that doesn’t need a computer or electricity to run (in contrast to competing products). Now we are looking for a word or short phrase to use in our marketing that describes this.

One alternative is “low-tech” (as the opposit of “high-tech”), but some of my co-workers find that it has a negative feeling.

“Simple” has also been voted down in other contexts, as being too negative.

We would use the word/phrase in this kind of context:

[Product name]:
Low-tech, low cost, high performance!

How would you describe something that is easy to use and doesn’t require electricity?

(None of us are native English speakers, so we’re not sure if our feelings about words are “correct”.)

Edit: Our target market are scientists, so they are used to working with complex equipment. If you are not using it yet, the “ideal” is still to use this equipment. That is why “low-tech” might feel negative. We are trying to target those that can’t afford the complex equipment or are tired of the complexity.