As soon as the sun starts shining, our wallets take a hit - from the cost of keeping cool to having a staycation, it all adds up. Key takeaways: Keeping cool during a heatwave can quickly push up household bills, with running a fan overnight costing around £5.67 a week and portable air conditioning averaging £15.56 a week. Summer extras at home can soon add up, from filling a paddling pool (£6.55) to watering the garden and hosting a BBQ, so it’s worth budgeting ahead.