Part 1: How do at-home solar panels work?
When I mention with not a small amount of enthusiasm that we have installed solar panels on our roof, I get a lot of questions:
- How do solar panels work?
- Am I using the power from my solar panels?
- What happens if I generate more power than I need?
- What happens when the sun goes down (or if it’s cloudy, rainy, etc)?
Let’s start with the basics…how do solar panels work?
As the sun shines on solar panels, the panels create DC (direct current) electricity – the same thing a battery creates. However, you need AC (alternating current) electricity to run your house. So the panels are wired to a box called an inverter, which converts DC -> AC. The inverter connects to your home’s power panel (where your circuit breakers are located).
Your house continues to operate as it always did – when you need electricity, you draw it from the power panel.
All of this is illustrated below:
This drawing came from an Australian site so the terminology is a little different. What they call the switch board we think of as the circuit breaker box or power panel. What they call the mains grid is our electric utility company. So it flows like this:
Am I using the power from my solar panels?
If the power panel is getting enough power from your solar panels, you do not use any electricity from the grid (your utility company). You are using the electricity you generated on your roof.
What happens if I generate more power than I need?
If the power panel is getting more electricity from your solar panels than you need right now, the excess electricity goes back to the grid – which means you are now a power plant! Your neighbors will use this power (and pay the utility company for it). You get credit for this excess power – your electric meter runs backward!
What happens when the sun goes down (or if it’s cloudy, rainy, etc)?
If the power panel is not getting enough power from your solar panels, the grid will supply the difference (and you are charged for this). Your panels can absorb sunlight even when it’s cloudy or raining (though much less than on a sunny day) – UV rays get through even when it doesn’t appear sunny out. It’s possible that you’re using more power than your panels are generating under these conditions. In that case, the power to your outlets is a combination of the solar power you are generating and power from your utility company.
At some point, as it gets dark, the panels stop producing power and all of your power needs are supplied by the grid. Basically, your house works just like it does before you had solar panels – the power flows from the utility company through your meter to the power panel and to your outlets.
In Part 2 I’ll explain how solar panels can save you money on your monthly electric bill, and maybe even generate income – stay tuned for Part 2 next week!