Do you have a question you would like to Ask The Sietch? Contact us or post your question in the Forums, and we will do our best to answer it. Got this one from the contact form.

Ryan asks:

Hello
I am an on the grid user. I was thinking about getting some solar panels to off set some of my electrical use. I contacted the local building department to find out more regarding the hookup of these to your existing home. They have no clue. So I ask you is it possible to add solar panels to a homes existing power system. Would I need batteries or can I hook it directly to my electrical box and put energy back onto the grid? My thought is it would at least lower my bill.

Thanks
Ryan

Hi Ryan. I used to work for a company that installed solar panels, and I can tell you that you have the exact same questions that just about everyone else has. Even in this modern world of wonderful technical advances in renewable energy it seems that a lot of local building resources are woefully under informed about how to go about using and installing these systems.

I will try to answer your questions in the order you asked.

Q “Is is possible to add solar panels to a homes existing power system”

A You bet it is! In fact it’s pretty simple. First you need to know a little about solar panels, and home electric systems. Solar panels produce DC power (the same kind you get from batteries), your home most likely runs on AC power. That means that they can’t “talk” to each other without a little help. To get around this problem you need a little box called an inverter. An inverter converters DC to AC. The solar panels go on the roof, or in a suitable sunny location, and the inverter goes next to the fuse box. See the image below.

Q “Would I need batteries or can I hook it directly to my electrical box and put energy back onto the grid?”

A Yes, both, one or the other. You can build a system with batteries, a system without batteries, a system connected to the grid, a system not connected to the grid, and any combination of the two (grid connected with battery backup). So why would you do one or the other?

Why add battery systems?
If you want to be disconnected from the grid you are only going to be able to use power when the sun is out, so if you add batteries to the system you can store up some of that energy for use later. This is a good setup for people who want to live way out in the middle of nowhere, or who want to be completely independent from the grid.

Why connect to the grid?
Most modern inverters allow you to be “grid tied” that means connected to the grid. When your solar panels are making more energy than you are using (you’re at work during a nice sunny day) then you send that energy to the grid and your power meter spins backwards, at night when you get home and start using more energy than your panels are putting out your meter will spin forward. At the end of the month if it spun backwards more than it spun forwards you won’t have a bill, in fact you will get a check from the power company. Neat.

Why connect to the grid AND use a battery system?
When the power goes out, your grid tied inverter is going to shut down your solar system. The reason it does this is because if the power goes out then its a good chance that someone will be out working on what they think is a dead line. It would be a nasty surprise if they picked it up and found a lot of electricity pouring out of it from your solar panel system. So contrary to popular belief the simple act of having a solar system doesn’t protect you from blackouts. What you need is is a solar system and a battery system. Inverters have sophisticated switching systems in them, if you have a battery backup system when the power goes out your grid tied inverter can switch over to your battery system and your power keeps going like nothing happened.

Why wouldn’t you need a battery system?
Most people don’t experience enough blackouts in a year to justify the very high cost of a battery backup system. Batteries are expensive, have to be taken care of, and eventually wear out. If you live in a place where the grid is pretty stable, you probably don’t need a battery backup system.

Q “My thought is it would at least lower my bill”

A I know this isn’t technically a question, but I am going to treat it as one. Yes it will lower your electric bill. For every watt of energy you produce from your solar system that means one less watt you need to buy from the grid. Plus if you make more than you produce you can sell the extra back to the electric company. Not to bust your bubble, but most electric companies pay you wholesale prices for the energy you sell to them, and then charge you retail prices when you buy the electricity, meaning you are not going to get rich that way.

It is more than possible to put enough panels on an “average” American home (read really big suburban home) to completely offset all your electric use. The limiting factor will be how much money you have to spend on your solar panel system. The nice thing about renewable energy is that eventually the systems pay for themselves. Through savings by not using energy from the grid, or from making money by selling the energy back eventually you will pay off your investment.

Some people will hem and haw about the fact that it can take 25 years to pay off your investment but here are a couple of things to keep in mind.

1. Solar panels when installed properly can easily last 50+ years
2. Non-renewable energy systems NEVER EVER EVER pay themselves off, they have an infinite payback period, you always have to shovel more oil/coal/gas into them, at an ever increasing cost.

I hope this has answered your questions. If you have anymore questions feel free to leave them in the comments.

Further reading:

Google talk on installing solar panels
getting money for your renewable energy system