Nor do many comparison sites. A variable direct debit (VDD) allows the supplier to take only the amount you owe from your account. A Monthly or quarterly direct debit usually means the supplier takes an agreed fixed amount from your account, but can be read as a VDD.  If it is an agreed fixed amount you can be sure the will not ...

Money supermarket does not give monthly variable direct debit when you input details for gas, yet it it appears on best buy list. Uswitch will only give me green tariffs.   Both sites are on the energy watch approved list - watch this space