With the London ULEZ being extended and the cost of living getting higher, a self-charging hybrid is a tempting choice, whether you’re looking at new or 2nd hand cars. By combining a petrol engine with an electric motor and battery pack, efficiency is improved and CO2 emissions are reduced.

You can get a self-charging hybrid in all manner of different cars and SUVs. There are tiny superminis like the Toyota Yaris, practical hatchbacks such as the Honda Civic, and even seven-seat SUVs like the Kia Sorento. In other words, there’s something to suit everyone.

How do self-charging hybrids work?

To put things as simply as possible, the battery is charged as you slow down or by the car’s engine in certain circumstances. This energy is then used to power an electric motor that can either drive the car on its own for a mile or two or boost the petrol engine.

The battery can also be used to power the car’s electrics without the engine running for an extended period when you’re stationary, or if you come off the accelerator on the move. All this lightens the load on the engine, improving economy and emissions.

How are they different from mild or plug-in hybrids?

Mild hybrids have much smaller motors and batteries that in most cases don’t allow the car to drive on electricity alone. Instead, the motor can assist the petrol engine while the battery also allows longer engine off periods than a regular petrol or diesel car. They’re cheaper to buy but don’t boost efficiency as much as a self-charging system.

Plug-in hybrids have much larger batteries than even self-charging hybrids. With ranges in excess of 50 miles in modern PHEVs, it’s possible to do much of your motoring on electric power alone. You do have to factor the cost of electricity into your running costs though, and PHEVs are pricier than self-charging hybrids. They also tend to have smaller boots than petrol or diesel models.

Will a self-charging hybrid save me fuel?

Probably, but it’s not guaranteed. Self-charging hybrids work best in urban areas, with the stop-start traffic helping to charge the battery and low speeds maximizing electric running. A good self-charging hybrid supermini can easily do 60mpg or better around town, although this will drop significantly when you hit the motorway.

Constant high speeds are still better suited to diesel engines, with a modern Golf TDi capable of over 70mpg if you’re careful. Expect a self-charging hybrid economy to sit in the 40s-50s. It’s also worth considering that many of these hybrids have small fuel tanks, limiting range.

What are the other advantages?

Buying a self-charging hybrid should keep you on the right side of any ULEZ zone, and there are other savings besides fuel, too. Self-charging hybrids’ low CO2 emissions help put them in a lower company car tax bracket than equivalent petrol or diesel cars.

Older pre-2017 hybrids may also benefit from exceedingly cheap or free road tax. You can check the DVLA website to see what any prospective purchase will cost every year.