Can a house run on solar power alone?

If you are new to solar energy, you might be wondering if it is actually possible to use solar power to meet all the energy needs of your home.

The answer to this question is a resounding YES. Not only is it possible to generate power for an entire house, you can also sell the excess energy by sending the electricity back into the grid.

Having said that, there are many things you should consider before deciding to move to solar.

As a new solar energy enthusiast, I did some research and made a list of basics below, that hopefully, will help you to make your decision.

Is it a good idea to go totally off-grid?

Well, it depends. I mean if you want to power a cabin located in a remote area where there is no power grid at all, it might make sense. However, generating electricity using solar power system doesn’t mean you should cut off your grid-connection. In fact, in many cases, only by having a connection to the network is it possible to justify having a solar energy system and make the investment more convenient.

If your house doesn’t have a grid-connection, you need to compare the costs of the connection with the costs of the solar power system. Also, you need to consider the pros and cons of each solution.

Using the off-grid solar power system has a big disadvantage of limiting your access to electricity during the day. The amount of power generated by the system changes seasonally and depends on the weather, which means you will have less electricity on cloudy days.

While it’s still possible to have electricity at night or when you need a boost of energy by installing batteries for your system. You should consider that having more batteries would increase the cost of the system considerably. Ultimately, if you decide to go off-grid, you have to carefully regulate your energy usage.

In this video, you can watch the shared experience of a family that has an off-grid system.

Otherwise, keeping the connection to the network will give you two important advantages:

• The first one is that through incentive programs, you can sell the excess of your power by sending it to the grid. In this way, not only will your system will pay itself faster but you will be able to make a profit off it in the long term.
• Also, considering the nature of electrical solar systems, they can’t generate power, evenly throughout the year. So instead of paying extra cash for batteries, you will take the power offset directly from the grid.

So generally speaking, it is very convenient to have that grid-connection.

How much sunlight does your house get?

This is a very important factor that will determine if you can install an appropriate system that meets your energy needs.

Usually, the solar panels will be installed on your home roof. The amount of sunlight your roof gets will decide the amount of energy that could be produced.

A solar contractor can estimate that just by asking for your home address and using a geolocation service like google maps, but, for an exact measurement on how much shade might be on your roof (due to nearby trees or other obstacles), roof tilt, orientation or the other factors that are involved, they might need to visit your house.

Another factor that decides the amount of sunlight you get is the weather. Even though there are solar panels that have high efficiency in generating power even on cloudy days, but none less it can heavily penalize your home system efficiency.

As obvious as it may sound, just remember more sunny hours mean more power is generated by each solar panel. So the total number of solar panels that you’ll need and consequently the cost of your system is influenced by the “sun hours” you get.

The “sun hours” is a technical term that refers to the hours of “peak sun”, which translates into 1000 watts of sunlight per square meter of surface.

You can have an estimation of how much sunlight hits your roof a year by visiting Google Project Sunroof. It also helps you to see how much you could save by using solar power.

How much energy do you need?

Solar system sizes are measured in kilowatt (kW) that refers to the amount of electric energy generated by solar panels per second.

Now, we don’t need to dive into physics lessons, just keep in mind the watt (W) is the measurement unit for power and 1 kW = 1000 W.

In order to decide the size of your system, you have to know your yearly energy usage. You can get that by looking at your energy bills and adding up your monthly energy usages, which is also what any solar expert installer will ask you for. Also, you may consider adding another 20% on your calculation because over the years the efficiency of the solar panels will reduce. This way you will be sure that your system will provide your needs.

Looking at your bills, you will find that the electrical companies charge you in kilowatt-hour (kWh). So you need to find out how much energy in kilowatt-hour (kWh) a solar power system could produce in a year. And in order to do the calculation, you need to know how many “sun hour” the solar panels will get once installed on your house-roof.

For a quick estimation, you can consider 4 hours as an average of peak sun in the U.S. Multiply this number by 365 (number of days in a year) and by the size of the system to find out the average amount of energy (kWh) that system could provide. For example, a 5 kW system can generate on average 7,300 kWh of energy per year.

4 (hours) × 365 (days) × 5 (kW) = 7,300 (kWh)

Now, you have a very rough idea of the size of the solar power system you need to cover all your electric energy needs.

How much a home solar power system will cost?

The total cost of a solar system for your house is determined by different factors such as:

• The system size
• The system components (Solar panels, mount type, inverter, wires, etc.)
• Installation cost
• Sales tax (varies by location)
• Maintenance cost (Some contractors have included this service at no additional cost)
• Government incentives (like ITC that make you save up to 30%)

So in order to find the best options for you, I recommend that you compare different solar contractor offers, locals and big ones.

If you are a U.S. resident, you can find incentives and policies by visiting the database of state incentives for renewables & efficiency.

To give you an idea, the average size of the home solar system installed in the U.S. is 6 kW which will cost about $20,000 not considering the incentive benefits that could reduce the cost down to around $13,000.

How long will it take to make profit from your system?

There is no unified answer to this question because of the different incentive policies in each state in the United States. It means that you need to do some calculations by yourself that are not very complicated:

• Get your total system cost (considering all government incentives and any possible local rebates that you can reduce from initial cost).
• Get your annual electricity bill rate, plus any additional rebates you may have from other incentive programs that give you credit for every kW/hour generated by your system.
• By dividing them, you will get a fairly good estimate of how long it will take for your system to repay itself.

Payback time = Initial investment ⁄ Annual return

Generally speaking, it can take an average of 6 to 9 years, depending on the size of your system and the incentives that you’ve got. That means, after this period you could potentially earn money from your system.

This is not an exact calculation and does not consider other factors such as solar panels performance reduction over the years, or the maintenance costs you may have due to the failure of some components.

Keep in mind that solar power systems have very long term warranties: Usually 10-12 years on equipment and up to 25 years on solar panels performance at 80%.

If you do the proper research to choose a good solar contractor, the home solar power system could be a profitable investment for your house. Not only will they save you a huge amount of money on your bill, they will also add extra value to your property, help the environment in the long run and after some years they could start generating profits.

If you want to know more about the environmental impacts of solar energy technologies, I wrote a detailed article with many references on it.