* Spot falls in Poland, rises in Hungary
* Czech solar tax upheld by constitutional court
PRAGUE May 16 (Reuters) - Czech Cal '13 electricity contract hovered around an all time low hit a day earlier, pressured by bearish fuel prices and the euro zone worries, while the spot power declined on milder weather and lower demand, traders said on Wednesday.
The Cal '13 rose 5 cents to 47.70 euros ($60.94) per megawatt-hour in late afternoon trade on the Prague-based Power Exchange Central Europe, with the discount to neighbouring Germany at 1.3 euros. It hit the same level in the over-the counter trade.
On the near curve, a bank holiday in Germany, with large changes in power consumption as a result weighed on day ahead power which fell 28.25 euros per megawatt-hour from 43.15 euros a day ago in the over-the-counter market.
"The holiday in Germany is the main reason behind the low spot plus why peak is below base today," one trader said.
A Czech tax on solar power producers was upheld by the Constitutional Court on Wednesday, keeping in place a part of the government's drive to trim budget deficits and tame a solar boom in the central European country.
Around the region, the benchmark German Cal '13 contract was down 17 cents to 49.90 euros in late afternoon trade on Germany's EEX.
Day ahead on Poland's POLPX exchange fell to 168.10 zlotys ($49.39) from 181.81 zlotys while electricity for Thursday on Hungary's HUPX edged higher to 55.63 euros from 46.36 euros.
Oil prices slid with world shares and the euro as investors fled from riskier assets due to the Greek crisis, while a surprise build in U.S. crude inventories helped send the WTI benchmark to a more than six-month low.
EUAs for December delivery, the bellwether carbon contract, were down 3 cents to 6.52 euros a tonne at 1539 GMT. ($1 = 0.7828 euros) ($1 = 3.4034 Polish zlotys) (Reporting By Maja Zuvela, editing by William Hardy)