Yes, these little differences are really annoying for old pedants like me. I think you’ll find, though, that while unit prices are usually quoted with only four significant digits, in calculations they are used with (at least) six. Suppliers fix their prices in various ways, but I think OVO decide on an ex-VAT price with six significant digits. The quoted prices with and without VAT are then quoted after rounding to four digits. Your first example uses a unit price of 22.06p, but it’s possible that the actual unit price is £0.220648.
An apparent ‘error’ of up to .005p would account for the 8p difference you calculated in the cost of 1695 units. So long as this rounding is applied consistently, accumulated errors will really be negligible. If you’re really keen to get to the bottom of this, you could perhaps use your browser’s developer tools to look at the myriad resources used to present the Billing details page. Here’s an example, showing just my electricity standing charge calculation for the month so far:
"electricityCharges": [
{
"sprn": "110000****018",
"standing": {
"netCharge": {
"pounds": "8.45"
},
"rates": [
{
"rate": {
"pence": "46.92"
},
"endDate": "2026-01-18",
"cost": {
"pounds": "8.4456"
},
"startDate": "2026-01-01",
"days": 18
}
]
},
You’ll see that a calculated value of 18 x 46.92/100 = 8.4456 is presented as 8.45. I’m sure you’ll agree that this is all quite reasonable.
