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How solar PV makes it affordable to buy an EV

Using real-life examples, we explain how solar PV, battery storage, time-of-use tariffs, smart charging and EVs work together.

1. Solar PV

At a domestic property, you will usually be limited to installing 4-5 kWh of PV without requiring permission from your district network operator. This will likely cost you between £5,000-10,000 (incl. Installation and VAT). The price varies due to access costs, brands, installation types, technologies and warranties.

2. Solar battery storage

We offer a range of different manufactured batteries and the prices vary due to a number of factors. The main factor is the capacity size. At present, we offer units that range between 2-15 kWh. The price may also be affected by the brand, features (charging from grid/working during a power outage), materials or specifications.

Typically, you can expect to pay between £4,000-8,000 (incl. Installation and VAT). The price would decrease when installing alongside solar panels, though, because of a reduced VAT from 20% to 5% and that the overall price would decrease as its a part of a package.

3. Time-of-use tariffs

Time-of-use tariffs are a type of differential tariff. Energy suppliers are able to offer tariffs with fluctuating rates at different times of the day. This is achieved by using the data provided by your smart meter.

The first energy supplier to introduce a time-of-use tariff was Green Energy UK. Since then, Bulb and Octopus Energy have both introduced their own versions. It is expected more suppliers will begin to offer time-of-use tariffs as smart meters are rolled out to homes and small businesses. This benefits both consumers and the grid as our energy use can be shifted to non-peak times.

4. Smart charging

There are smart chargers available that work specifically with microgeneration systems like a domestic solar PV system. The charging current is automatically adjusting alongside your panels’ production so the energy is fairly split between your home and EV.

You also have the option to charge from grid too. This means for a faster charge and if you have a time-of-use tariff, you can charge your EV with free or cheap electricity.

Typically, a smart charger can cost anywhere between £750-1,000 (incl. Installation and VAT). There is a government grant for electric car home chargers. The Electric Vehicle Homecharge Scheme (EVHS) grant is provided by the Office for Low Emission Vehicles (OLEV). The grant covers up to £500 for the initial outlay of the charger.

5. Electric vehicles

Electric vehicles (EVs) are usually cars or vans that use electric motors and rechargeable batteries rather than a combustion engine. However, other EVs can include rail vehicles, aircraft and spacecraft.

Currently, the most popular electric car in Europe is the Nissan Leaf. According to Nissan’s website, the starting price is from £27,995. The range is up to 168 miles under WLTP combined cycle test conditions. The battery capacity is 40 kWh.

The Nissan Leaf is also eligible for the maximum government grant of £3,500 under the Plug-In Car Grant.

This price is in comparison to the UK’s most popular car, Ford Fiesta, that has a starting price of £15,670 on Ford’s website.

When together, what does this all mean

Go Ultra Low has a really informative website with calculators embedded. In the home charging calculator, we entered the Nissan Leaf 40 kWh 2.Zero Auto and a home charger power output of 7 kW. We chose 7 instead of 3 as we install the Zappi charger that has a 7 kW power output.

The default domestic electricity costs (p/kWh) was 16.5p. We changed the radius of the EV to 168 miles.

The results:

The Nissan Leaf would take just under six hours to fully charge, at a cost of only £6.60 — that’s about 3.9p/mile. The average petrol or diesel car costs around 12p/mile, meaning it would cost you around £20.20 to drive the same distance.

In 2017, the average distance travelled in the UK by car was 7,134 miles. This means the annual running cost of your Nissan Leaf would have been £278~. If you had a petrol or diesel car, it would have cost you £856~.

Average weekly road fuel price statistics have been published since 2003, by the UK Government’s Department for Business, Energy & Industrial Strategy:



On average, fuel prices have increased by 3.79% year-on-year.

You would have even lower running costs if you were on a time-of-use tariff. Octopus Energy has an EV tariff called Octopus Energy Go. This tariff has a rate of 5p/kWh between 00:30-04:30 am (four hours). The cost per mile would, therefore, be 1.2p. If you exclusively charged the car at this rate, you would have had an annual running cost of £86~.

Octopus Go’s “peak” rate (the 20 hours around 00:30-04:30) varies a little depending on where you are in the UK but hovers around the 14p/kWh mark. This means that if you’re planning to fully charge your car every night, for two hours it would be at the 14p/kWh rate. This could be an additional cost of around £138~ per year.

Go Ultra Low estimates that in comparison to the Ford Fiesta Zetec, the Nissan Leaf could save you £440 in VED Road Tax over three years.

Go Ultra Low also states that the maintenance costs for an EV are about half of that for a petrol or diesel car. The Car Experts estimates this to be around £171~ per year, meaning an EV would be around £86~.

Without an EV, the UK Government estimates that the average home uses 3,800 kWh of electricity per year. Based on Go Ultra Low’s default rate of 16.5p/kWh, this is an annual cost of £627~.

Adding a PV and storage system

If you incorporated a 4 kW solar PV system, a 5 kW battery and a 7 kW Zappi charger, you may pay around £10,000 (incl. Installation and VAT). The system alone could produce anywhere between 3,500-4,000 kWh depending on a number of factors. You can expect a saving of at least 50% per year on electricity bills, as some of your energy usage will be when the panels aren’t producing. That’s a minimum saving of £313.

The battery would store any surplus energy and allow you to use this free energy when the system isn’t in production. Day-to-day, this could help increase your savings from anywhere between 51-100%.

If we assume that the system reduces your expenditure by 85%, that is an annual saving of £533~. The government reported that between 2017-18, the average home’s electricity bill increased by 8%. If this trend continues, your savings would also increase year-on-year.

Your initial outlay would be £34,495:

40 kW Nissan Leaf (27,995 – 3,500 government grant = £24,495)
4 kW solar PV system, 5 kW battery storage & 7 kW Zappi charger (£10,000)

Your average savings would be:

YearYearly savings (£)Total savings (£)

This table takes into account a possible annual increase of 8% for the unit price of electricity. It also takes into account a possible annual increase of 3.79% for fuel prices. It also carries an annual VED tax saving of £146.67 based on Go Ultra Low’s comparison of the Nissan Leaf to the Ford Fiesta Zetec.

For this set-up, you may export around 10% of your solar production. Under the new Smart Export Guarantee, you will be entitled to earnings for every kWh that is exported back to the grid from your energy supplier.

Octopus Energy is already offering 5.5p/kWh before the legislation has been introduced. Based on 10% of 4,000 kWh per year, you could earn £220 over 10 years.

In this scenario, you would also still be paying for 15% of the average home’s energy usage, 3,800 kWh per year. If we assume this is at 14p/kWh under the Octopus Energy Go tariff, you would pay £1,156.02 over 10 years (accounting for the potential 8% unit price increase year-on-year).

This means after 10 years, you would have spent (34,495 + 220 + 1,156.02 – 19,584.91 =) £16,286.11.

Comparison against an ICE vehicle alternative

If you were to only purchase the Ford Fiesta Zetec, your initial outlay would be £15,670.

Your average losses would be:

YearYearly losses (£)Losses (£)

This means after 10 years, you would have spent (15,670 + 22,437.39 =) £38,107.39 on your car and electricity.

This article does allow for assumptions but predicted figures have been calculated using both UK Government historical data and information from reliable sources. This case study shows that it is economical, over the long-term, to go green.

Both tables don’t take into account several factors, for example, the depreciation of value for the vehicles. However, we feel it’s important to note that after 10 years, it is predicted that electric cars will be far more economical to purchase and maintain than the average petrol or diesel car.

We would also like to stress that most solar panels are warranted to retain between 80-90% of their original output after 25 years. Most battery models are warranted for 10 years but are designed to last 20+. This means by going green, you would be future-proofing your home and continue saving for the long-term.

We used examples of a new EV and ICE vehicle but you would be able to purchase older models or even spread the costs through a financing option. We also offer a range of different financing options for solar PV, battery storage and the rest of our available technologies.

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