Solar Panels

Can Solar Panels Power a Whole House?

By:Michael Johns

powering a whole house with solar panels

So you want to power your whole house with solar panels.

I admire your quest.

And I’m not about to kill your dream, the opposite in fact.

It’s very possible to run a whole house with solar power.

You just need to understand how the equipment works and the amount of electricity you need to generate.

For a normal house, you can offset your whole energy bill with enough solar panels! 

But it is important to understand you’ll still be reliant on the main grid at certain times.

In this article, you’ll learn how to power a whole house with solar panels. Plus, we’ll look at running completely off-grid buildings.

Below you’ll find two different methods as a normal house operates differently from an off-grid property when it comes to solar panels.

So let’s get stuck in.

How to Completely Power Your Home With Solar Panels

We’ll start by looking at how you go about running a normal house with solar power. This is the most common way systems are set up as it gives you the best performance at any time.

How Home Solar Panels Works

A residential solar panel system is grid-tied. This means your house can draw power from both the solar panel and the main grid. Plus, it means you can send excess electricity to the mains grid and be rewarded with credit. 

This is an important concept to understand as it underpins how you run a whole house with solar panels. During peak sun hours you will be able to generate plenty of electricity from solar panels. Generally, this is 4 or 5 hours a day when you need to do all of your electricity production. This is because at night you won’t be able to use your solar panels. The aim during peak sunlight hours is to produce the total amount of electricity you use over a 24 hour period. You will use some of this electricity to run your house and the excess will be sent to the main grid in order to earn credit.

When your solar panels stop producing enough electricity, you will need to draw power from the main grid. Hopefully, during this time you will have earned enough credit from your solar panels that it offsets your main grid energy usage.

How solar panels power a house
Solar panels send power to your house and to the main grid

This is the most practical and cost effective option. You can also look at installing backup batteries to store your own power. This is great for an emergency outage, but it will be very expensive to add enough battery capacity to run your whole house completely off-grid.

With this knowledge, we can now go through how to calculate the number of solar panels to run a whole house.

  1. Work Out Daily kWh Consumption

The first thing you need to do is work out how much energy you use each day. You can find the information on your utility bill. It will be marked as a total in kWh. Usually this is the total energy consumption per month. To work out the daily kWh simply divide the total by number of days.

Let’s say it’s 800kWh per month divided by 30 days:

800kWh ÷ 30 days = 26.6 kWh per day.

  1. Work Out Daily Wattage

Next we need to convert the kWh (Kilowatt-hours) into Wh (Watt-hours) per day. This will make it easier to work out the number of solar panels later.

Remember, 1 kilowatt is 1000 watts.

So just multiple the kWh by 1000 to get Wh.

26.6 kWh x 1000 = 26,600Wh per day. 

  1. Divide by Peak Sun Hours

As we discussed, they only produce most of their electricity during peak sun hours. This is when the sun is strongest in the middle of the day. Usually this is roughly between 11am and 3pm. Around 4 hours per day. 

The aim is to generate all your electricity needs during these hours. To work out how much energy your solar panels need to generate per hour divide the daily Wh by peak sun hours.

For example, 26,600Wh ÷ 4 Hours = 6650 Watts.

So you need a solar panel system that generates 6650 Watts.

Peak sun hours vary depending on where you live. You can use this map for an estimate in your region:

  1. Number of Solar Panels Required

Now we know the total power requirements of a solar panel system, we can work out how many panels you will need. 

To do this divide the Total Watts by Individual Panel Watts.

The average residential solar panel is 250 watts.

In our example that means 6650 Total Watts ÷ 250 Watts = 27 solar panels.

In this scenario, to power a whole house you will need 27 solar panels.

Running an Off-Grid Building with Solar Power

If you are thinking of running a whole building from solar power completely off-grid then a different approach is needed. This is because you won’t be able to lean on the main grid when electricity production slumps from your solar panel, e.g. at night or cloudy weather. You will be at the mercy of the sunlight, weather, and seasons. 

How Off-Grid Solar System Works

Quite often you will find these systems installed in remote cabins, boats, and campervans where energy usage is low. The solar panels generate electricity in the same way but excess is stored in batteries for later.

The solar panels generate electricity which is sent to a battery for storage. Then you draw power from the battery through a power inverter. This has two benefits. Firstly, it creates a way to store electricity. Secondly, it delivers a stable power output which can be inconsistent from smaller solar panel installation. 

Inverter charge controller wiring diagram for solar panel
Solar panel charges a battery which is then used to for power
  1. Total Daily Energy Consumption

The process for working out the size of the system you need is very similar to the steps above. Total daily energy consumption will be harder to work out as you won’t have utility bills to rely on. You will need to calculate this based on the power of the appliances you intend to run.

  1. Divide by Peak Sun Hours

With your total energy consumption you need to divide this by the peak sun hours in your area. Use the information in step 3 above.

  1. Number of Solar Panels

Again, divide your total daily wattage by solar panel power. Use the same formula as step 4 above. 

Off-grid solar panels come in many different types and sizes depending on the application. You can find 50 watt, 100 watt, 200 watt and many more.

  1. Battery Storage Capacity

The additional step here is calculating the amount of battery storage capacity you require. This is important to ensure you have enough batteries to give you enough power to run through a night or during bad weather. 

You can find many different sizes of batteries and you should match this to the amount of energy you want to store. For example, if you use 500Wh a day in an RV you might consider adding 500Wh of battery capacity so you have a full 24 hours backup if your solar panels are offline. There is no right or wrong rule here as off-grid systems have an impossible number of variables to take into account. 

FAQ on Solar Panel to Power a Whole House

I’m sure you have a number of questions still buzzing around your head. Let’s answer the most common ones:

Can a house fully run on solar power alone?

Yes, it is possible to run a full house on solar power. Generally, you will still need to be connected to the main grid in order to draw power. This is because solar panels don’t produce electricity at night and you will need electricity from the mains during these times.

How many solar panels would it take to power a house?

The average American household uses 20 to 30kWh each day. This would require between 21 and 30 standard residential solar panels rated at 250 watts. The exact amount of solar panels is based on total energy consumption, peak sun hours, and equipment power.

Can solar panels power a house 24/7?

Technically no, solar panels can’t power a house for 24 hours a day. This is because they don’t produce electricity at night and perform poorly in early morning and evenings. To achieve complete running from solar power you either need to offset the main grid with credit or install battery storage to produce electricity outside of peak sun hours.

Can solar panels power your whole house during a black-out?

Don’t expect your solar panels to run your house during an outage. The systems are grid-tied and will not produce power to your house when supply from the main grid is offline. This is to protect engineers working on the main grid during a black-out. If you want to power your house with solar panels during a black-out you will need to add a battery backup.

Running a Whole House with Solar Panels Summary

By now you should have an understanding of the ins and outs of using solar panels to run a whole house.

To be honest, you will still be connected and drawing power from the main grid at certain times. Your best option is to install a big enough system to completely offset your utility bill each month.

Leaning on the main grid is the only option if you want guaranteed electricity 24/7. 

Although, for remote buildings and vehicles with low energy requirements it’s perfectly possible to live using solar panels and battery storage.