Running the numbers: How many solar panels do I need?
There's no question that installing solar panels on your home is good for the climate – and your wallet. Taking the time to calculate how many solar panels you need can help you make sure you get the best value, right from the start.
There's no question that installing solar panels on your home is good for the climate – and your wallet. Taking the time to calculate how many solar panels you need can help you make sure you get the best value, right from the start.
Just by running the numbers and spending a bit of time figuring out your energy needs, you'll be able to make sure your solar panel installation is fine-tuned for energy independence, maximum cost savings, and a positive environmental impact.
In this guide, we'll take you through everything you need to know to figure out how many solar panels it takes to power a house. Let's get into it…
How many solar panels will I need on average to power a house?
There are a few things that can affect how many solar panels you'll need for your home. Factors such as house size, solar system size and annual energy consumption all need to be considered to get to an accurate figure.
That said, if you’re thinking ‘how many solar panels do I need for a 4-bedroom house?’ or a 3-bedroom house, or so on, the table below shows you the average panels needed for various house sizes:
View the table in full-screen here.
Of course, these are rough estimates, based on installed examples. Every property has its own unique factors that affect how much power is generated, like irradiance, roof pitch, roof orientation, local meteorological factors and shading.
You’ll be able to find out more about how these factors affect your property when you get a quote, along with a more refined estimate of how many panels you’ll need.
How to calculate how many solar panels I need
Want to determine exactly how many solar panels you'll need to power your home efficiently? We've put together a three-step process below to help guide you to the right number with minimum fuss.
1. First, you'll need to work out your energy consumption by finding out your daily energy consumption in kilowatt hours (kWh). Don't worry, it's easier than it sounds – our friends at British Gas have put together a detailed guide here.
2. Now it's time to estimate solar panel output.
Work out the production ratio of your solar panels: calculate how much electricity your solar panel produces under the average sunlight and weather conditions in your area. In the UK, the average production ratio is around 3.225 watt-hours (Wh) per day per watt (W).
Then multiply that number by the wattage of your chosen solar panel.
So, for one 350W panel, you'll come out at 395.06kWh per day. While one 450W panel will generate 507.9kWh.
3. Finally, divide your daily energy usage by the daily output of one panel to calculate the number of panels you'll need.
There's quite a lot to process there. So we've put together a handy infographic below to give you a quick and easy way to remember the steps.
What are the factors that affect the number of solar panels I need?
There are several factors that could influence the number of panels your house might need. Let's look at some of the most important considerations.
Your household energy consumption
Your household energy consumption has a big impact on how many solar panels you'll need. Want to calculate your average consumption? Grab all your recent energy bills and look for your kilowatt-hours (kWh) figure on the bills. Add up all the figures and divide it by how many bills you're using. That will get you your monthly average. For a yearly total, simply add together your monthly kWh over a 12-month period.
Solar panel efficiency
The efficiency of a solar panel is defined by how well it can convert sunlight into usable electricity. Now, the exciting news is solar panel efficiency is getting better all the time. That said, the level of efficiency can vary by solar panel brand and even model. The material used for a panel can influence its efficiency too, with monocrystalline solar panels tending to be most efficient, closely followed by polycrystalline and thin-film solar panels. The most common domestic panels tend to be polycrystalline.
Read more about solar panel efficiency in our dedicated guide here.
Solar panel location and sunlight coverage
This basically means where you live! Where you and your solar panels are in the UK will have an impact on their energy-generating performance. In the UK, solar panels in the south perform slightly better than in northern areas – so that’s also something to factor in to your calculations.
There are some great online resources that can estimate peak sunlight hours and potential energy output for your area. Try PVWatts Calculator to get estimated figures in just a few seconds.
Amount of roof space for solar panel and orientation
Of course, before you start your solar journey, one of the big questions is how many solar panels can I fit on my roof?
A larger roof will accommodate more panels but features such as skylights might also inhibit solar panel fitting, so you'll need to take that into account.
Panels need to ideally be south-facing with a slight tilt towards the west to maximise exposure to sunlight, as well as being installed at the optimum tilt angle—in the UK this is typically between 30° and 40°.
Finally, it's important to consider things like trees and other buildings that could stop your panels from catching the sun's energy at different times of the day.
What restrictions are there on the number of solar panels you can have?
As with most elements of UK building law, there are potential restrictions on the number of solar panels you can install. It's also important to consider compliance for financial incentives and any grid connection limits. Here are some key things to think about:
Planning permissions
Luckily, most domestic solar installations are considered 'permitted development'. That means you won't need to worry about planning permission when you install them. But there are exceptions. If you live in a conservation area, a listed building, or another specially designated area you might need permission. If you're in any doubt, it's best to contact your local planning authority before you start to install any solar panels on your home.
Financial incentives
You probably know there are financial incentives available if you choose to install solar panels – which is great news. Just be aware there are sometimes specific installation requirements that you need to stick to in order to get them.
For example, the Smart Export Guarantee (which lets you sell excess electricity generated by your solar panels back to the grid) has set criteria on the capacity you're allowed. You can find out more about the scheme in this guide from our friends at British Gas.
Grid connection limits
When installing solar panels on your home, you'll typically need to inform your Local Distribution Network Operator (DNO). And if you're putting in a larger system, they may limit the solar capacity connected to the grid. Generally, smaller systems can connect with fewer restrictions, but larger systems will require approval.
Building regulations
Modern solar panels tend to be lightweight, and they're extremely safe. But it's still crucial to comply with structural safety and electrical standards for the solar panel installations in your home. It'll prevent potential roof damage, and it'll help you avoid electrical hazards. Considering things like proper mounting will prevent wind or weather-related damage, while sticking to electrical standards will reduce fire risk and help safeguard both your property and the grid.
Start your journey into solar savings with Hive
If you’re ready to transform your energy usage and harness the power of the sun, here at Hive we’re totally ready to help…
Check out our top-rated solar panels and get set for a brighter future!
Let’s Get Sharing
More Articles
Wait or worth it: How much do solar panels cost in the UK?
Solar panel grants: Everything you need to know
