Heating fuels
The provisions on energy taxation allow private individuals to purchase for their own use liquid gas in cylinders that is "in free circulation in another EU member state", and to bring it into Germany free of tax: for example, propane for camping. This is conditional on their transporting such goods themselves. The tax exemption does not apply to other liquid fuels, though. This means that if you bring liquid heating fuels with you from another EU member state the tax becomes due at the time you move them into Germany, that is, at the time you cross the German border.
National provisions on the possession and storage of hazardous materials must be observed.
Wood pellets
As wood pellets are not energy products within the meaning of energy taxation legislation, and are thus not subject to energy tax, you may buy this product in another member state and bring it to Germany without paying any duty.
Transiting non-EU states while travelling within the EU
Where you transit a non-EU state (Switzerland, for example) when travelling from another EU country to Germany, you may import fuel products in the allowed quantities mentioned above without having to pay duty if you are able to show that the products are from free circulation in the EU. This will be easier if you can show invoices/receipts.
Contact and assistance
The Central Information Unit of the German customs administration (Zentrale Auskunft Zoll) is there to help you and will answer your questions by telephone, post, or e-mail.