The question that everyone wants the answer to. Annoyingly, the answer is not that simple. Be prepared to do the research, but from the examples we have seen, it can be so worth it.
There are many factors to take into consideration when converting a gas car, the best place to start is looking at the original car and how many aspects you would want to keep from that. Older cars will be much easier to convert as they do not have all of the technology that you get from modern cars. Rich Rebuilds, a Youtuber who focuses on Teslas and EVs, has a video looking into this.
For example, a common choice is the classic VW Beetle, and this would be quite an easy choice for an EV conversion. This is partly because they do not have any complicated touchscreens or sat naps etc and there are already many choices of kits on the market. These kits can be on the expensive side though around $20,000-30,000 before labour costs.
One of the suppliers that has been around for a while that does the VW kits is EV West. They specialise in Beetles, Porsches, and various other classic VWs. They have narrowed their scope to these vehicles as parts need to be tailor-fit to the retro powertrains. This allows them to offer a one-stop-shop for the crate kits.
With a mounting plate, you can mount a motor right on the transmission. Then you just need to connect the batteries depending on the range that you want, add the controller unit which connects the pedals to the motor, and then you a pretty much ready to go. There will of course be some more parts involved, such as the charger, wires and fuse boxes but companies like EV West will include those within the kits. Be aware that not all kits include the batteries.
The batteries is where the main part of the cost comes in. One battery can be tens of thousands of dollars by going with Tesla cells. There are other options as well though with used Nissan Leaf batteries, or if you know what you are doing, using individual cells from laptop batteries.
To give you an idea on range, the 50-100 kW range should suit for a daily driver giving around 100-250 miles depending on the type of vehicle.
The most popular choice seems to be going for a brand-new powerful motor that costs thousands of dollars, but some go to junkyards and use an old forklift motor which is a fraction of the price. If you do decide to do this, then just make sure to not if it is DC or AC, as yo may need to invest in a converter. It is also worth noting that 1 kW is roughly 1.34 horsepower.
Another YouTuber, Botts Fine Vids, shows an overview of his Karmann Ghia conversion. He had converted a Beetle before the Ghia so has some experience with conversions. This build is incredibly thought out, Bott’s knows exactly what is needed and does a good job breaking down and explaining the process.
Amazingly, Bott’s is able to keep the cost for the conversion to under $20,000 by doing the work himself, keeping things to the minimum and by taking a compromise on range but is still able to dramatically improve the performance.
We know that this is not an definitive explanation of how to build an EV but hopefully this helps to guide you in the right direction. If you were thinking of building a restored Land Rover with roughly 300 miles of range and air conditioning then you would be looking at a cost of about $100,000.
But, if you are capable of taking on a lot of the work yourself and have an old Miata knocking around, then you could possibly get it converted with a range of 150 miles for about £15,000. It depends just how much you are willing to do yourself and if you are comfortable using some old junkyard components.