Learn Hardcore Japanese: syouenekaden wo tukattara, denkidai ga yasuku narimasu. - If you use energy-saving appliances, your electricity bill will go down.

省エネ (shōene) is a contraction of 省エネルギー (energy saving). When used as a compound, 省エネ家電 literally means energy-saving home appliances or energy-efficient appliances. It’s common to drop の in fixed technical or marketing terms to make them shorter and catchier. If you wanted to add の, 省エネの家電 is also grammatically correct.

Why is the particle を used after 省エネ家電, and why not は or が?

を marks 省エネ家電 as the direct object of the verb 使う (to use). In this sentence the focus is on the action of using energy-efficient appliances. If you used は, you’d be emphasizing 省エネ家電 as the topic. If you used が, it would mark it as the subject, but here 使ったら is a conditional clause built on the verb 使う, so を is required.

What grammatical form is 使ったら, and what does it mean here?

使ったら is the past tense plus ら conditional form (the たら form). It means if/when you use energy-efficient appliances, focusing on the result after the action. In this context it’s best translated as if you use or when you use.

Why is 電気代 marked with が, not を or ?