( ( On ( sweltering ( summer days ) ) ) ( , ( ( city ( power supplies ) ) ( ( ( are often ) ( ( ( taxed ( by ( increased ( air ( conditioning use ) ) ) ) ) , ) ( as ( citizens ( struggle ( to ( beat ( the heat ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN On) (S (VP (VBG sweltering) (NP (NN summer) (NNS days))))) (, ,) (NP (NN city) (NN power) (NNS supplies)) (VP (VBP are) (ADVP (RB often)) (VP (VBN taxed) (PP (IN by) (NP (VBN increased) (NN air) (NN conditioning) (NN use))) (, ,) (SBAR (IN as) (S (NP (NNS citizens)) (VP (VB struggle) (S (VP (TO to) (VP (VB beat) (NP (DT the) (NN heat)))))))))) (. .)))
On sweltering summer days, city power supplies are often taxed by increased air conditioning use, as citizens struggle to beat the heat.
(ROOT (S (NP (NP (DT A) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN increase)) (PP (IN in) (NP (NN length)))) (VP (VBZ happens) (PP (TO to) (NP (NN metal) (NN railroad) (NNS tracks))) (PP (IN during) (NP (NP (DT the) (NN heat)) (PP (IN of) (NP (DT a) (NN summer) (NN day)))))) (. .)))