Thinking about going solar? One of the first questions homeowners ask is: How many solar panels will I need? The answer is, it depends on your household’s roof square footage and typical electrical energy use. It depends on your existing wiring and structural nuances. It depends on the solar panels you plan on using. It depends on your budget. And it depends on your plans.
If that sounds confusing, don’t worry. This guide breaks it down into simple chunks to help you get started on your solar journey. And remember, the question isn’t necessarily ‘how many solar panels can I fit on my roof?’ – rather, it’s ‘how many solar panels do I need?’ Keep that specific question in mind, and you’re off to a perfect start.
Understanding your energy needs and roof space
Start by checking your annual electricity use on your energy bills, usually in kilowatt-hours (kWh). The average UK home uses about 3,000 to 4,000kWh per year, but this depends on how many people live there, appliances and lifestyle. Detached homes tend to use the most; mid-terrace and flats tend to use the least (per Ovo Energy). A smart meter or energy monitor provides more precise data.
Now, your roof size limits how many panels you can fit. Most panels are around 1.7m² and produce between 300 and 400 watts (W). Higher wattage panels generate more power but may cost more and take up slightly more space. South-facing roofs with no shading perform best, but east- or west-facing roofs can still work pretty well. And just so you know, ‘shading’ includes shadows from trees or even nearby chimneys. The best way to make sure you’ve got an optimal setup is to get a professional survey before you commit to solar panels.
How to calculate how many solar panels you need
Now it’s time for the next step. Let’s calculate how many solar panels your household needs. You can estimate how many panels you’ll need to invest in via the following simple steps.
- Find your annual electricity use in kWh (see the previous section of this article).
- Divide by the average annual output per kW of solar in your area, typically 850-1,000kWh/kW in the UK. This means how much electricity one kilowatt of installed solar panels typically generates over a whole year, based on your local sunlight conditions.
- This gives the system size in kW to cover your use.
- Divide this system size by your chosen panel wattage (in kW) to find the approximate number of panels.
For example, based on 3,500 kWh/year and 900 kWh/kW average output, with 350-watt (0.35 kW) panels:
- 3,500 ÷ 900 = 3.89 kW system size
- With 350 W panels: 3.89 ÷ 0.35 = about 11 panels
Typical systems are:
- One- to two-person homes: four to seven panels
- Average families (three to four people): nine to 12 panels
- Larger homes (five+ people, electric heating): 12 to 18 panels
Note that you don’t have to cover 100% of your electricity to save money. Smaller systems reduce grid use and bills, and some start small and add later.
Panel efficiency, future planning and professional advice
More efficient solar panels convert sunlight into electricity better than standard panels. In other words, you don’t need as many to yield the same results. So, if your roof area is limited, choosing higher efficiency panels lets you fit fewer panels while still meeting your energy goals. However, these panels often come with a higher price tag. It’s a balance between available space, budget and desired system size.
Looking ahead, your electricity needs might grow. For example, if you plan to charge an electric vehicle at home or install an electric heat pump for heating and hot water, your energy consumption will increase significantly. These changes mean you might want a larger solar system now or one that can be easily expanded later, so factor that in to avoid costly upgrades in the future.
Lastly, while rough calculations are useful to get started, every home has unique features. Roof shape, shading from trees or buildings, orientation towards the sun, and even your home’s wiring all influence how well a solar system will perform. We can’t underscore the importance of a professional solar survey enough. This ensures your system is the right size, neither too big (which wastes money) nor too small (which leaves you buying more power from the grid). A well-designed system maximises your savings and helps you get the best return on your investment.
Get your solar panels from Electrical Innovations
Ready to take the next step? Give Electrical Innovations a call for a free, no-pressure chat. We’re a local Derby team that’s been helping homes go solar since 2006. We’ll listen to what you need, design the perfect system for your home, and ensure a smooth installation for long-term rewards.
Let’s work together to get the most efficient solar system possible installed in your home. Reach out today.
