I have both electric and gas running into my home ... with gas being used for hot water (Infinity system) and cook-top.

Electricity usage obviously varies with time of year (heaters in winter), lighting, clothes & dish washing, etc etc.

My gas bill, however, shows a very wide variation where I would have assumed, in a household of just two adults, it would be pretty even throughout the year?

Mid-winter months are double the summer months.

Since we on average take the same number/time for showers, and use the appliances that draw hot water much the same too, why would gas usage graphs show definite highs and lows?