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How much can a solar PV system reduce your reliance on the grid?

July 2018

Reducing electricity bills is the main driver for many customers looking to add photovoltaic solar panels to their home, but just how much can a solar PV system reduce your reliance on the grid? We looked at one of The Phoenix Works founders, Matt Morgan’s own 4kW home solar PV system to find out.


Matt & his family live in a three-bedroom, semi-detached home in Leeds and use around 4,600kWh of electricity per year. Having initially installed a solar PV system at his home in 2011, Matt was so impressed with the amount of power generated and savings on his electricity bill that he upgraded to an even bigger solar system in 2015.


In the area of the UK that Matt lives, he could expect his panels to generate around 3,800kWh a year – which, for context, is approximately the figure the Department for Business, Energy and Industrial Strategy uses as the average yearly electricity consumption of a UK household. Although the amount of energy generated by solar PV systems will vary throughout the year, as some days are brighter than others, on a particularly sunny day in June Matt’s solar panels generated 29kWh of energy in just 24 hours. On this specific sunny day, 29kWh was considerably more energy than Matt and his family required to run their home, using only 12.5kWh of electricity.


So where does all that excess solar energy go? During the day, Matt’s home was powered with 8.9kWh of electricity generated by his solar panels, meaning he didn’t have to buy any electricity from the grid whilst the sun was shining. The remaining 20.1kWh of energy would have been exported back to the grid as it was not needed in his home as it was being generated. On any day a solar PV system will generate more energy when the sun is at its highest / brightest, peaking between 12-2pm. But this pattern in most cases does not match the demand of electricity in an average home. Your morning coffee and hot shower sees a surge in energy use as does cooking dinner and watching evening television.


This is where battery storage can help maximise the return on investment from your solar pv system, allowing you to store energy when there is excess being generated for use in the evening. Without a battery installed, Matt’s home would be able to use the energy from his solar panels as it was being generated, but not store any of the ‘excess’ power. So, during the night – when the solar panels weren’t generating – Matt would need to buy 3.6kWh of electricity from the grid.


Fortunately, Matt’s home has a 13.5kWh Tesla Powerwall installed, and this changes his situation considerably. “We decided to add a battery to our home last year,” says Matt. “Both my wife and I work during the day, meaning that a lot of the electricity our solar panels are generating isn’t actually being used by us. So we decided that the ability to store that energy for use when we get home would be the logical thing to do.”


Because the Powerwall is able to store the ‘excess’ energy generated by his solar panels, Matt is able to store up his renewable electricity for use at a later time – when the sun isn’t shining, or when his household demand is particularly high. During the periods when his solar panels weren’t generating and when his household usage peaked during the day, Matt was able to use the electricity stored in his Tesla Powerwall rather than buying electricity from the grid. So just how much electricity did Matt buy from the grid? Almost none – a mere 0.01kWh. Essentially, Matt’s home was entirely energy independent on June 24th 2018.


Now, this was a particularly sunny day, and on a more typically cloudy and drizzly British summer day, we might not have seen such a high level of performance from the solar panels. However, across five months from May to September 2018, with solar panels and a Tesla Powerwall installed, the amount of energy Matt’s household imported from the grid fell from 1619kWh to just 18kWh. That’s less than two days’ worth of average energy consumption, spread across five months!


“Since having the Tesla Powerwall installed, our electricity savings have risen from around 30% to around 80%,” says Matt. “On sunny days we are able to power our home 100% from our solar and battery system, meaning that some days we don’t buy any electricity from the grid at all. It’s a great feeling!”

“The ability to generate and use our own dedicated renewable electricity gives us a sense of independence and pride that we’re doing our bit to help the shift away from fossil fuels.”

So not only has Matt’s solar and battery system resulted in a dramatically reduced carbon footprint from generating and storing his own renewable energy, his increased independence from the grid means he is saving a huge amount on his bills as well.


To find out how The Phoenix Works can help you find the right solar PV solution for your home click here.



EV charging bay

29kWh generated in

24 hours from 4kW solar

PV system

Electricity from the grid

reduced to 3.6kWh 

Electricity bills reduced

by 30%

Home 100% powered by

solar energy by adding

battery storage

Phoenix Works icon
The Phoenix Works is part of Phoenix Renewables Ltd

Company Registration Number: 7477370

VAT number: GB 109 6957 79

Registered Address:

Griffin House, 161 Hammersmith Road, Hammersmith, W6 8BS