Finding the chase and cutting to it

This seems an odd time to write this post, as there is no anniversary coming up. But it is a conversation that comes up every so often. Here’s my answer to it.

When we first got our Nissan Leaf Tekna in January 2014, it inspired this section of the blog, and ultimately, the podcast of the same name, Driving off the Grid. Many of us early adopters made this choice because we wanted to lower our carbon footprint. The question is, did we manage it?

Working out of total cost of ownership, carbon dioxide wise.

Basically, through car wings, we knew our efficiency was around 5 miles per kilowatt, or 0.2 kWh per mile. We’ve done 44,682 miles since we’ve owned it. Therefore, about 8,936.4 kWh, or 9MWh.

Now, we got solar cells in August 2014, so our first 4,000 miles were driven from the UK grid. After that, around 55% were charged from the grid, the other 45% from our solar cells.

(These are all averages. During the summer, we were 100% solar powered, during the winter, 35%. Now we have the house battery, nearer 75% all year round. My best ever efficiency for a journey was ten miles per kW, my worst was 3.7 miles per kW, five per kW is what we tended to average over a month.)

So, 4,000 used 800kWh which would have generated 335 kg carbon dioxide. The grid supplied 22,375.1 miles *.2 kWh = 4,475.02 kWh, over 12 years 8 months. Our solar cells provided 18,306.9 kWh at 0g of CO₂ per kWh. Let’s split the remaining 4,475.02 kWh over that time, circa 353.292 kWh pa.

Given those figures as our base line, we then look at the carbon intensity of the grid, as provided by NESO.

See the table below for how that gives our carbon footprint per annum for each year of ownership.

Year	Grid kWh Consumed	UK Grid Carbon Intensity (g/kWh)	Estimated CO2 Emissions (to 2 dp in kg)
2014	353.292	419	387.64
2015	353.292	350	123.65
2016	353.292	300	105.99
2017	353.292	250	88.32
2018	353.292	230	81.26
2019	353.292	210	74.19
2020	353.292	180	63.59
2021	353.292	170	60.06
2022	353.292	160	56.53
2023	353.292	150	52.99
2024	353.292	124	43.81
2025	353.292	126	44.51
2026 (Jan–Sep)	353.292	126	44.51
Total	4,475.02		1,322.45 kg

So, our travels in our Leaf have caused around 1.3 tonnes of CO₂ to be generated.

The producing the battery would have caused ~3.6 to 4.8 tonnes of CO₂ to be generated. Thus our total carbon footprint has been 3.9 tonnes.

That’s an awful lot for a green vehicle.

Shall we compare? Petrol and Diesel are much easier to compute. They have fixed CO₂ footprints per mile.

Petrol car would have generated around 280 grams per mile, so 12,510.96 kg. A Diesel one would have generated around 277 grams per mile, so 12,376.914 kg.

So, essentially, we have saved a maximum of 7,588.51 kg of CO₂. We have used considerably less than doing those journeys with a car with an internal combustion engine (ICE).

But that is not the full picture. We swapped out a 2008 BMW 650i. It generated 430g of carbon dioxide per mile. That car would have generated 19,213.26 kg instead. By comparison, we saved 14,290.81 kg.

Now, many would argue that building a new car uses more carbon dioxide than running an old car. I have ignored what the total cost in terms of carbon dioxide for making the BMW or the Nissan. I have assumed they are equal, but I did take out and include the battery.

When we look at the engine block, pistons, exhausts, spark plugs, etc, servicing costs, they probably equate. Of course, our battery and car are still on the road and still performing as well as they did coming off the showroom floor.

Per mile, and in its life-time, the EV is using 110g carbon dioxide per mile and this is just going down, as > 90% of the energy we use for the car this year has come from our solar cells and home batteries.

At some point, our battery is going to need replacing. I think it makes sense to do that.

In terms of financial cost, a new 24kWh battery would cost us ~ £2,500 fitted and including VAT. A 40kWh battery would cost us ~ £4,800 fitted and including VAT. We’d still be better carbon dioxide generators than using the old ICE car. In general, ICE produce more CO₂ as they get less efficient, pistons get clogged, pipes get blocked… I ♥ our Leaf.

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If you’d rather listen than read, check out the partner episode on the Driving off the Grid podcast, published on the 2^nd October 2026.