Two weeks after moving into my flat, I had a letter from my landlord asking to increase the Nebenkosten by an extorionate amount (around 25%, I think), saying that the other tenants had to pay large overpayments because of large consumption of fuel and also because fuel prices had risen.

The landlord asked me to agree to the increased cost, rather than demanding it, so I just ignored it, and my Nebenkosten have remained the same. I didn't feel inclined to pay back money for other people's previous heating bills. I took advice at the time and was told that the landlord can enforce an increase in Nebenkosten only at the standard times for vacating flats (April/Sept).

However, since I have only just moved in, I am obliged to stay until Sept 2008, according to my lease. Does this mean that the first date at which they can increase my Nebenkosten will be September, or will it be April?

Is there a way I can make sure that a future increase won't be because I am paying back for heating when I wasn't even a tenant?

kfc.

Normally you always receive a detailed billing for your hot water and heating consumption charges and are always charged only for the tenancy period.

What your landlord tried to do was to adjust the charges to the expected consumption - if the charges stay the same, you will most likely have to pay a hefty lump sum once the reconciliation between the provisions and the actual charges will be made.

I've just reread the letter I got and, now, taking into account your post, I can see that it may not be as sinister as I first thought (although they were asking to increase the Nebenkosten from 150 CHF to 230 CHF!!). I still think it was sharp practice to have me sign the lease on the understanding of costs of 150, though, which they must have known at the time that the other tenants were now paying 230CHF.

However, I might reconsider in the light of your post. In the UK, fuel prices are supposed to be going down now. Is that the same here? If that's the case, then maybe I needn't worry too much.

kfc.

fuel prices are going down (maybe) due to the poor performance in the dollar. Oil is internationally traded in $$$$$'s.
Dollar has performed miserably against the £ sterling, however has been pretty static regards the Swiss Franc.