First Edition energy cards can sell up to $35 each, but only if they are fully graded PSA 10s (see also our article How and Why to grade Pokemon cards). The average 1st Edition card is going to sell for about $2 each. This means that energies are among the cheapest of First Edition cards that you can get.
Part of the reason why original energy cards are not worth anything is that they do not do anything special. The design from the original energy cards was copied for the very first sets of Pokemon. This means that they do not really stand out from the crowd. In case you wanna sell your Pokemon cards, check out our article TOP 5 sites to sell Pokemon cards.