Oil radiator heaters. https://www.amazon.com/Rellorus-Radiator-Adjustable-Thermostat-Electric/dp/B0B2DNHYMC/ref=sr_1_3_sspa?keywords=oil+filled+radiator&qid=1670007337&sr=8-3-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzN085WFVLU0Q3VkczJmVuY3J5cHRlZElkP... safe and low energy. Get one with tipping safety switch so if it falls over it'll auto shut-off.