Temperature inside refrigerator = t₂ °C

Room temperature = t₁ °C

For refrigerator,

${{{\rm{Heat\,given\,to\,high\,temperature}}\,\left( {{Q_1}} \right)} \over {{\rm{Heat\,taken\,from\,lower \,temperature\, }}\left( {{Q_2}} \right)}} = {{{T_1}} \over {{T_2}}}$

${{{Q_1}} \over {{Q_2}}} = {{{t_1} + 273} \over {{t_2} + 273}}$

$\Rightarrow {{{Q_1}} \over {{Q_1} - W}} = {{{t_1} + 273} \over {{t_2} + 273}}$

$\Rightarrow 1 - {W \over {{Q_1}}} = {{{t_2} + 273} \over {{t_1} + 273}}$

$\Rightarrow {W \over {{Q_1}}} = {{{t_1} - {t_2}} \over {{t_1} + 273}}$

The amount of heat delivered to the room for each joule of electrical energy (W = 1 J)

${Q_1} = {{{t_1} + 273} \over {{t_1} - {t_2}}}$