How Many Solar Panels Do You Need to Charge a Lightbulb?

Solar Power - All Night Long... A solar storage battery can provide solar energy day or night

Solar panel output depends on a wide variety of different factors, from panel efficiency, to the amount of panels in your system, to where you live in the UK, and many other things.

So why does it matter how much electricity our lightbulbs use? Well it has been stated by energy conservation groups that our lightbulbs account for 20% of our electricity bills – so how many solar panels do you need to power the lightbulbs in your home?

How Much Electricity Do Appliances Use?

Home Appliances Electricity Usage – kWh/year Cost Over Year
Fridge-Freezer 427 kWh £62
Plasma TV 658 kWh £95
Desktop PC 166 kWh £24
Electric Cooker 317 kWh £46
1 Lightbulb 109 kWh £12

To calculate the usage of 1 lightbulb we knew that a 60 Watt lightbulb would use up 0.06kWh of electricity per hour. We decided by looking at each of the seasons that 5 hours was a good average for the amount of time a lightbulb would be on each day. This worked out as 0.3kWh per day and 109kWh per year.


But Who Has One Lightbulb?

Nobody! We had a look online and decided that 9 lightbulbs is a good average amount of lightbulbs for many homes and bungalows. Accounting for all of those lightbulbs we can work out that these cost us upwards of £108 per year in electricity costs! AND that is if you remember to turn them off!


How Much Sun Does A Solar Panel Need?

You might think that solar panels need red-hot summer sunshine to work but this is not actually true, whilst solar panels are more efficient on clear sunny days they still produce electricity on cloudy, rainy, foggy or cold days.

On average across the whole year we get around 4 hours of bright clear sunshine a day, which equates to 1460 hours of sunlight across the year. (So to calculate your panels minimum output 4 hours of sunshine a day is a good place to start).

So with 9 lightbulbs in our home, running for 5 hours a day on average, this means we would need 981 kWh of electricity to power them for the whole year.


So, to figure out how much electricity we need from our solar panels we divide our lightbulbs electricity requirements by the minimum sunlight our panels will get each year:

981 kWh by / 1460 hrs of sunlight per year
= 0.67 KW’s

After this we must know the KW’s each of our solar panels can produce. So if we get a high efficiency 120W solar panel, this equals 0.12KW’s. So we divide the energy we need by the amount of energy each solar panel can produce to find out how many solar panels we need.

0.67KW / 0.12 KW
= 5.58 panels.

Which means that you would need 6 solar panels to provide the electricity needed for 9 light bulbs in your home for a whole year.

12-16 Panels

Most UK solar panel systems are made up of between 12-16 solar panels, averaging at around 3.5 KW’s for the whole system. So, if you opt for a standard solar panel array you wont just be saving on the 20% of your bill made up by your lights. You would be saving considerably on the costs of every single appliance.

How Many Panels Would Fit On Your Roof?

BUT! We Only Use Lightbulbs At Night!

 Well, most of us are out of the house during the day and most of us only use our lightbulbs in the evening… but thanks to solar storage batteries you can benefit from your solar electricity day and night.

A solar storage battery will store electricity generated by your panels during the day for use in the evening. As soon as the sun goes down and your panels stop generating, your solar storage battery would discharge the electricity it has stored across the day.

Battery manufacturers claim that you can cut your bills by a further 50% with a solar storage battery, as you would be buying less electricity back from the grid during peak hours.

How Much is Solar Storage?

Solar Panels are “contagious”

Keeping up with the Joneses used to mean getting a bigger car to match your neighbours’ or making sure your lawns are neat and tidy – but in the 21st century, it means going solar.

EPC - small changes

A recent study suggests solar  is “contagious” as people are more likely to install PV panels if their neighbours have.

This is most likely down to the fact that seeing panels on a neighbour’s house serves as a constant reminder that they’re enjoying big savings on their bills AND receiving regular tariff payments.

How long is the solar payback in your neighbourhood?

A new report published by The Guardian highlights the difference in the time it takes for solar panels in different regions to payback their investment. It’s no great surprise that southern cities get on average more hours of sunshine per year than the north, but Met Office statistics show that the difference is not actually that great.

Unsurprisingly, cities in the south came out tops, with Plymouth, Exeter and Truro named as the three cities with the highest return on investment for domestic solar panel installations. In Plymouth, it takes only 8.4 years for a domestic solar panel installation to pay for itself, compared with the national average of 9.5 years.

You will notice on the table to the right that all the northern regions show payback will be less than 10 years, and given that the term in which the FiT payments are guaranteed for is 20 years, you can see why solar is still such a popular investment.

To read the full article – click here.

MP reaffirms solar as a great investment

This week we received a letter from MP Gregory Barker, with some information concerning solar and the Government’s plans for renewables. The letter remained positive with its backing of renewable technology and also commented on the fact that a 4kW system now costs £11,500 less than two years ago.

As it currently stands, installing solar panels at this price could pay for themselves within 8 years due to the Feed-in-Tariff (FiT) payments and the reduction in electricity bills. The FiT payments would be guaranteed for a further 12 years (20 years in total) and the savings on your electricity indefinitely, resulting in serious earnings by the homeowner.

With the FiT payments being indexed linked and set to rise with inflation each year, along with increased savings as energy prices rise year-upon-year, solar panels remain a smart investment.