Like a lot of car owners, I’m thinking about replacing my diesel car with one powered by battery. I’ve identified a model that I’d like, but I’m puzzled by the infrastructure I’ll need. As far as I can tell, it’d be cheapest to charge the car overnight, using a suitable tariff like Economy 7. But I’m reluctant to commit to installing a charger until I’ve worked out what to do next.

Should I check with my energy supplier first to see if it has a suitable tariff, or go ahead and get the charger installed in the hope that I can find a suitable tariff afterwards. Or should I just buy the car and sort out charging issues later? SP, London

Your caution is understandable since electric cars, while promoted by the government for their green credentials, made up only 1.1% of car sales this year and, although cheaper to run, they cost more than the average traditional car to buy.

For pioneers like you, there’s the issue of rapidly evolving battery and charging technologies and the dearth of public charging points. According to David Lewis, founder of the advice website electriccarhome, the cost of charging depends on where, when and how often, you charge. Charging at home overnight on an off-peak tariff would cost 5p per kWh rising to 30p at a motorway service station. At work, or at a hotel, it could be free if you have an obliging employer or all-in deal.

A number of energy companies offer cheap night-time rates for electric car owners, depending on where you live.

Find the provider first, preferably an eco-friendly one since that’s the whole point, and get a free smart meter installed before you bring the car home. If you have off-street parking, it’s safer and faster to get a dedicated charging point installed and you get a £500 government grant towards the cost.

Lewis advises asking your electricity supplier to confirm that the type of charging point you have in mind is “smart” enough to charge automatically during the off-peak charging window. Once you’re up and running that 5p off-peak tariff could buy you 10,000 miles for around £132 a year.

If you need help email Anna Tims at your.problems@observer.co.uk or write to Your Problems, The Observer, Kings Place, 90 York Way, London N1 9GU. Include an address and phone number. Submission and publication are subject to our terms and conditions