[tex]\displaystyle\bf\\Formula~pentru~calculul~energiei~este:\\\\E = P\times t\\unde:\\E=Energia~in~KWh\\P=Puterea~in~KW~~~(Puterea~dezvoltata)\\t=timpul~in~ore\\\\E_{util\^a}=1,8~KW\times8~ore=14,\!4~KWh\\\\\eta=90\%\\\\\eta=\frac{Energia~util\^a}{Energia~consumat\^a}\\\\\\\eta=\frac{14,4~KWh}{Energia~consumat\^a}\\\\\\ Energia~consumat\^a=\frac{14,4}{\eta}=\frac{14,4}{90\%}=\frac{14,4}{0,90}=16~KWh~consumati.\\\\Costul~energiei~este:~~16~KWh\times 2 \frac{Lei}{KWh}=\boxed{\bf32~Lei}[/tex]
