Solar Power FAQs

Common Questions about Solar PowerHere are the answers to some commonly asked questions about home solar power:

1) What are some of the basic components needed for a home solar power system?

Basic home solar power components include solar panels, inverters, and various switch controls for safety. More elaborate systems often include charge controllers and battery banks to store power for night use, and many even include a gas generator as a backup source of electricity. View the solar energy components category on this site to see diagrams and more details.

2) What different types of solar power exist?

The two common types of solar power for home use are Photovoltaic (PV) and Passive Solar or Solar Thermal.

3) What are some of the common units and formulas needed to determine my power consumption?

1 horsepower (HP) is equal to 750 Watts, 3,400 BTU’s equal 1 kilowatt (kW), and a Kilowatt Hour is 1000 watts consumed for 1 hour.

Most household products in the USA will use 120 Volts, with the exception of large household appliances like clothes dryers and ovens. In other parts of the world 240 volt systems are more commonly used.

Watts = Volts * Amps, so as an example 240W = 120V * 2A

4) What type of electricity do solar panels produce?

DC (direct current) power is produced by solar PV panels. This is essentially the same as battery power. Since most household appliances run off AC (alternating current) power, the electricity generated by solar panels must flow through an inverter to change it into AC power for home use.

5) How much photovoltaic (PV) power will I need my system to generate?

Once you have determined your daily load or power usage, you can use this formula to estimate your PV power need:

PV Power Required = Total Daily Usage(kW hours) / # of hours of daily sunlight

The # of hours of daily sunlight will vary from one location to another and will probably range from around 3 hours to as high as 5 or 6 hours for locations close to the equator or high sunlight desert regions like Arizona and New Mexico.

6) How much roof space will the solar panels take up?

On the average, plan on about 100 square feet of roof space for every kilowatt (kW) produced. For example, many residential solar systems are designed to generate somewhere between 3 and 6 kilowatts, so one of these types of home systems could take between 300 and 600 square feet of roof space.

7) How do I calculate the energy consumption of household items?

This can be a bit tedious, but it is an important step in the process when considering producing your own power. Most household items have labels, although they may not show the number of watts used. For example, I just looked at my computer printer and it shows 120V and 0.6A on its label. Multiplying these two numbers together gives us 72 watts, which is the number of watts used per operating hour. Determining your home’s energy consumption is important, so that you know how big of a solar PV system is required to meet your energy needs.

8) What kind of batteries are used in home solar systems?

The batteries used for backup battery banks in a solar system are not your normal 12 volt car batteries. These are special, deep cycling batteries that are considerably more expensive. It is not uncommon for these to cost $200-$300 each and they are the types that are used for electric golf carts.

9) I’m considering a Photovoltaic (PV) System for my home, but I’d like to do some things right now that can lower my energy use. What are some things that I can do?

Before designing and building a large expensive PV system, it is important to look at ways to reduce your energy usage. Replace incandescent bulbs with CFL bulbs, which last longer and use a fraction of the electricity. Instead of all electric appliances, you may want to consider using propane or gas for heating or your refrigerator, since these use large amounts of electricity. Here is a link to the US Department of Energy website that contains a good deal of information for consumers on how to save energy, estimate energy use, and how to make your home more energy efficient.

10) What is Net Metering?

Net metering is a term used by regulators to describe the situation where a utility customer can get monetary credit for electricity they generate and send back to the utility company. With your home solar system, net metering would allow you to generate excess electricity during the day and use it at night, without having to use batteries.

Net meters look a lot like other outdoor electrical meters, but unlike ordinary meters, these ones spin both forward and backwards depending on whether you are drawing electricity from the utility grid or producing excess power and sending it back to the grid. Many of today’s meters are digital, so they don’t actually spin forward or backward, but you get the general idea.


Grid-Intertied System

Grid-Intertied Solar Power SystemThe grid-intertied or utility-connected system is probably one of the most popular and common systems for those having access to the grid or a utility service provider.

The diagram to the left, shows some of the main components and the basic configuration for this type of setup.

Basically, what happens here, is that you install a photovoltaic (PV) system at your house, which is connected to your household electrical system. However, you are also connected to the power grid through your electric meter. When your solar panels are generating more electricity than you need, it is fed back into the grid and it is like your electric meter is running backwards. At times when your solar panels are not generating enough power to meet your needs, then your meter is running forwards and you are using electricity from your electric provider.

This approach helps you reduce your monthly electric bill, but also provides you with the stability of always having the amount of electricity that you need, regardless of varying weather conditions that may affect the efficiency or electric output of your PV panels.