Ok, 25% of 27.5q BTU = ~ 7q BTU So we need extra 7q BTU of electricity, right? Which is about 18% of 37.8! So, not 7, not 9, we would need at least 18% extra

Ok, 25% of 27.5q BTU = ~ 7q BTU So we need extra 7q BTU of electricity, right? Which is about 18% of 37.8! So, not 7, not 9, we would need at least 18% extra electricity. TLDR: Your math was wrong!