• Solar
  • Mar 06, 2020


We’ve compared two similar BMWs: the BMW 320d and the BMW i3. The first an ICE (the new name for any car with an internal combustion engine) and the second an electric vehicle (EV). Both cars are relatively compact in size and heading up towards the high-end of the market, ideal for perhaps a retired couple or single person needing a sensible but luxurious daily drive.

The i3 is well-loved EV, capable of doing around 193 miles on a single charge with a 42KWh battery. It compares well in size and in specification to the 320d, which is also an excellent daily drive.

We’ve made this comparison much tougher for the EV by including the cost of installing a solar PV system to our user’s home. Will our test-case user – a retired couple driving 10,000 miles per year – be able to recoup this extra outlay with the savings they’ll make on electricity and running costs? Could they even make savings? And all this in the knowledge that they’ve considerably reduced their carbon footprint in doing so.

Let’s see….

Driving cost breakdown

Purchase price

If you want to purchase the i3 outright, you’ll pay £35,080. For the 320d, you’d pay around £34,500 upfront. Surprised? The price of the EV is pretty similar – only a difference of around £580.

However, we’ve got to add the cost of getting a solar PV system installed. We’ve added a cost of £5,918 for the panels and installation. You’ll also need to get a home EV charger fitted – again we’ve included this one-off cost in the comparison. Overall, you will pay just shy of £41,000 to purchase an i3, a home charger, and have solar PV installed.

BMW i3 vs. BMW 320d. Does going electric really save you money?
We added a 5kW solar installation to this comparison for lower costs over every mile


Most new cars nowadays are bought on finance, and our user is doing just that. You can still save money if you finance your PV and EV instead of buying them outright. We’ve assumed a £4,648 loan deposit for both the car and the solar installation, plus a £432 monthly payment. This compares well to the 320d’s pricing of a £5,175 payment upfront and £262 per month cost. (We’re assuming a 48 month loan term for these figures.)

While the ICE is cheaper so far despite the initial higher deposit amount, you might be persuaded to go for the electric bundle because you value finding a cleaner way to get around. You’re also investing in an asset that will add value to your home and save you money on your energy bill too.

Fuel and electricity

We’ve estimated that you’ll pay around £25 per month to charge your EV up. This takes into consideration the fact that you’ll have to buy some of your electricity from roadside charging points, which are much more expensive than charging at home. Despite this, the cost of charging the i3 compares very favourably to the cost of fuelling the 320d – for this, expect to pay at least £149 per month.

If you’re able to charge your car at home using off-peak or night time electricity rates, you could be paying just 5p per kWh every night. For the i3’s 42kWh battery, you’ll pay just £2.10 to fully charge the car, which is pretty impressive.

Carbon emissions

An easy win for the EV! Greatly reduced CO2 emissions and local pollution are one of the main reasons why you should consider an EV, and the i3 delivers in this regard. You’ll emit at most 0.98 tonnes of CO2 per year running the i3. This figure comes from the average carbon intensity of grid energy, though the figure will be much lower if you go for a green tariff and your own PV generation. For the petrol 320d, you would treble this with 3.03 tonnes of carbon emitted per year.

As we stated, you can further reduce your CO2 emissions by changing your electricity tariff. Most electricity providers now offer an EV-specific tariff, and these tariffs generally source all their electricity from 100% renewable resources. If you’re combining a renewable energy tariff with a solar installation, chances are you can power your i3 without emitting any CO2 at all.

Running costs, servicing, tax and insurance

More reasons to make considerable savings with an i3. The i3 is actually cheaper overall to run every month, which is excellent news for anyone looking to save some money. In the last few years, you might have expected to pay more for your insurance if you drove an EV. Now it is just important to shop around, as some insurers are more open to this market sector than others.

The electric i3 is in insurance group 29, whereas the 330d is in more pricey insurance group 31. You won’t experience a massive saving on your insurance, but it is a saving nonetheless. As ever, insurance costs are highly dependent on your personal circumstances and driving history, so its best to obtain a quote before deciding what to buy.

You’ll also make savings when it comes to road tax. You won’t pay to tax the i3, as electric vehicles are exempt from road tax. The 320d is not exempt from road tax, and you should expect to pay £145 every year for the privilege of driving on our roads.

Servicing is much the same story – as we know, electric motors are much simpler than internal combustion engines. With fewer moving parts, there is less to go wrong. Less to go wrong equals lower servicing and maintenance costs.

Solar PV is pretty low-maintenance, and you won’t require anyone to come out and service it or maintain it after it’s been installed. However, we’ve added a small sum to cover any cleaning costs.

Overall, expect to pay £117 per month to run your i3, versus £135 to run the 320d. A significant saving over the course of a year.

Expected savings

This comparison takes a figure of 10,000 miles per year. If you drive further than this you’re likely to experience greater savings.

BMW i3 and a 5KW PV system BMW 320d
Total upfront cost (if you decide to pay upfront) £40,998 (£35,080 for the car and the charger and £5,918 for the PV) £34,500
Loan deposit for financing £4,648 £5,175
Monthly loan payment £432 £262
Loan period 48 months 48 months
CO2 emissions p/a 0.98 tonnes 3.03 tonnes
Cost per mile 2.64p 13.53p
Monthly electricity/fuel costs £25 £149
Tax, insurance and servicing £117 £135
Solar Running Cost £0 N/A
Total monthly costs £574 £546
Annual cost (year 1) £11,532 £11,727
Annual cost (years 2 – 4) £6,884 6,552

As we can see, the costs are very similar after four years. But at this point, with the loans paid off, you own both the car and the PV. After 10 years, and with 100,000 miles driven, you’ll have made a £8,127 saving if you buy the i3 and PV.

Should I buy a BMW i3?

If you’re buying a new car and want to do the right thing by the planet, an electric car like the i3 is the way to go. What you might not know is that electric cars cost less to run and require substantially less maintenance than conventional cars, which can make your life much easier too.

See how much you could save using our free EV and clean energy tool!