Why is there a strong burning plastic smell from my consumer unit only at night?

A burning plastic smell coming from your consumer unit is one of the most serious warning signs your home's electrics can give you. The fact that it happens mainly at night is an important clue, and it helps narrow down the likely causes. Why it happens at night At night, certain electrical loads run for long periods without interruption. Storage heaters charge overnight on cheaper Economy 7 or Economy 10 tariffs. Electric vehicle chargers run for several hours. Immersion heaters, tumble dryers, and overnight appliance chargers all place a sustained demand on circuits. A loose connection or overloaded cable that causes only gentle warmth during short daytime use can overheat significantly when that same current flows continuously for six or eight hours. Heat builds up, insulation softens, and you get that unmistakable burning plastic smell. Common causes Loose connections at the main switch, individual circuit breakers, or the busbar are the single most common cause. Even a slightly loose terminal causes arcing and localised heat. An overloaded circuit, particularly a ring final or radial circuit feeding a high-draw appliance, can cause cables inside the consumer unit to run hot. A failing or ageing MCB or RCD can develop internal resistance and generate heat without tripping. Rodent damage to cables entering the consumer unit can cause insulation breakdown under load. An old or non-compliant consumer unit, particularly one made from non-fire-retardant plastic or without a metal enclosure, is itself a fire hazard if internal heating occurs. What you should do right now 1. Do not try to investigate the inside of the consumer unit yourself. 2. If the smell is strong, persistent, or you see discolouration, smoke, or scorch marks, switch off the main switch immediately. 3. Do not reset any tripped breakers. 4. If you see flames or smoke, leave the property and call 999. 5. If there is no immediate danger but the smell is present, call a registered electrician tonight, not tomorrow. How to find a safe electrician Always use an electrician registered with a Part P competent person scheme. In the UK, look for NICEIC, NAPIT, or ELECSA registration. You can verify registration on each scheme's website. Do not use an unregistered person for consumer unit work.