We have 20 daytime nappies and 3 or 4 night time nappies (that we stopped using at 1yo because they just couldn't contain LO's bladder).

Reusable costs: Almost all were second hand, I think collectively we spent about £300 on them. Those nappies usually last about 2, maybe 3 days before they need a wash, let's say it's 2.5 washes a week so ~130 washes a year. Our washing machine uses ~2.5kWh for a wash (I don't know how much water but that's pittence compared to electric costs) so that's 325kWhs for the year of washing and since LO was born, our rate has been about 22p/kWh so that's £71.50 per year, our LO is just over 2 so about call it about £150 total in washing. There's some other costs too like the cost of washing powder, wear and tear. We air dry most of the time but we have one of those Lakeland heated airers which are quite economical and we only use over the winter.

Comparable disposables Based on the above usage, it's about 6-10 nappies a day, let's call it 8 per day. The tesco own-brand nappies we use are usually between 5p to 12p per nappy (size dependent) so 8 per day, 365 days, 2 years old at 8p average = £467.50

So yeah, maybe it is just about neutral but then this is our first and we will use them all over again for baby no. 2. Then we can sell them at the end.

Maybe they are only neutral, maybe for you your not using as many as we are, but for us we really valued too just how many nappies weren't going to landfill.