Oil Filled Radiator vs Convection Heater: A Factory Comparison

We've been building both oil-filled radiators and convection panels on the same floor since 2009. Buyers ask me this every week: which one should I stock? The honest answer is that it depends on your customer's room and how they use it. Here's the breakdown I give them.

How they actually heat

A convection heater pulls cold air in at the bottom, runs it over a hot element, and pushes warm air out the top. It heats the air fast. Turn it on and you feel warmth in a minute or two. Turn it off and the warmth goes away almost as fast.

An oil-filled radiator works differently. The element heats diathermic oil sealed inside the fins. The metal body gets hot, then radiates and convects heat into the room. It's slower to start — maybe 10 to 15 minutes before you feel real warmth — but it keeps giving heat after you switch it off. That stored heat is the whole point.

For a bedroom, most buyers prefer the oil unit because it's silent and the heat feels gentler. For a workshop where someone needs warmth now, a fan-assisted convection unit wins.

Wattage and room size

The rule we use in the factory: 100W per square meter for average insulation, 120W for poor insulation, 80W for well-insulated new builds. A 2kW oil-filled radiator covers roughly 20 square meters. A 1.5kW convection panel covers about 15 square meters.

If a buyer tells you they need an electric heater for a large room, don't just sell them the biggest unit. Two 1.5kW units on opposite walls heat more evenly than one 3kW unit. We see this in returns data — oversized single units create hot spots and cold corners.

Running cost reality

A 2kW heater running four hours a day at €0.30/kWh costs about €2.40 a day. That's €72 a month. This is why the energy efficient electric heater question keeps coming up. The truth is that all resistive heaters convert nearly 100% of electricity to heat. There's no magic efficiency gap between oil and convection. The savings come from using a thermostat properly and heating only the room you're in.

Where oil-filled units can save money: they keep radiating after the thermostat cuts power, so the element cycles less. In a well-insulated room, that can mean 10-15% less run time over an evening. Not huge, but real.

Noise and thermostat control

Convection heaters with fans make noise. Cheap ones make annoying noise. If your customer wants a silent electric heater, oil-filled is the safe pick. No fan, no clicking relay if you spec a good thermostat.

On thermostats: mechanical bimodal thermostats swing 3-4°C. Electronic thermostats hold 1°C. For a wifi smart electric heater, you need electronic control anyway. We build both, and the electronic version adds about $4 to the BOM at 200 pcs MOQ. Worth it for the retail price bump.

Safety and certifications

Every unit we ship for EU retail carries CE, RoHS, and ERP compliance. UK buyers need UKCA. Don't let a supplier tell you CE covers the UK — it doesn't anymore.

Key safety features to spec: tip-over switch, overheat cutout, and IP rating if it's going near water. A bathroom unit needs IP24 minimum. We see buyers try to pass a standard panel as a bathroom heater and get burned on returns.

What to stock

If you're a distributor building a range, here's what I'd do:

• Oil-filled radiators: 1.5kW and 2kW, 7 to 11 fins. Core SKU for bedrooms and living rooms.
• Convection panels: 1kW and 2kW, wall-mounted or freestanding. Fast heat, lower price point.
• One wifi smart model in each category. This is where the margin is.

MOQ is 200 pcs per model. Lead time is 15-45 days depending on whether you need custom packaging or just private label on our tooling. Private label electric heater programs are straightforward — your logo, your manual, your carton. Custom tooling is a different conversation with a different timeline.

The honest takeaway

There's no universal winner between oil-filled and convection. Oil-filled gives slower, steadier, silent heat and works better in bedrooms and well-insulated rooms. Convection gives fast heat and lower cost, better for workshops and quick warm-ups. If you're sourcing from an OEM electric heater manufacturer in China, ask for both and let your customers' room sizes decide the mix. Stocking only one type limits your range and your margin.