Oil Filled Radiator vs Convection Heater: Factory Guide for Buyers

If you're sourcing electric heaters for a European or North American distributor, you'll eventually face this question: oil filled or convection? Both sell. Both have loyal customers. But the wrong pick for your market means returns, complaints, and dead stock. Here's the difference from someone who's built both on the same line since 2009.

How They Actually Heat

A convection heater pulls cold air in at the bottom, runs it over a finned element, and pushes warm air out the top. It's simple. Heats a room fast. The moment you switch it off, the warmth stops. That's the trade-off.

An oil filled radiator heats diathermic oil inside sealed columns. The metal body becomes the heat source. It takes 15–20 minutes to feel warm, but it keeps radiating for another 20–30 minutes after shutdown. That thermal mass is why people say oil filled feels "softer."

For a wall mounted electric heater in a bathroom or hallway, convection wins on response time. For a bedroom where you want steady overnight heat without a fan noise, oil filled wins. This is the core of the infrared heater vs convection debate too — infrared heats objects, convection heats air, oil filled sits in between.

Wattage and Room Size: The Numbers Buyers Get Wrong

Every year I see purchase orders for 2000W oil filled radiators destined for 8m² bedrooms. That's overkill. The rule we give clients:

• 1000W for up to 10m²
• 1500W for 10–15m²
• 2000W for 15–22m²
• 2500W+ for open-plan or workshop spaces

A 2000W unit pulls roughly 2 kWh per hour. At UK average rates around £0.24/kWh, that's about £0.48/hour to run. A 1000W low wattage electric heater halves that. If your market is cost-sensitive, stock 1000W and 1500W first. The 2500W units sit on shelves unless you're selling to tradespeople.

Build Differences That Affect Your Margin

Convection heaters are cheaper to make. No oil, no sealing process, fewer leak tests. Our FOB on a 2000W convection panel runs about 18% below the equivalent oil filled radiator. MOQ is 200 pcs for both, lead time 15–45 days depending on whether you need custom tooling.

Oil filled radiators have more failure points. Weld quality on the columns matters. If the oil leaks, you get a return and a bad review. We pressure-test every unit at 1.5x working pressure. Ask your supplier what their leak test protocol is. If they can't answer, walk.

Convection units fail mostly at the thermostat or the element. Cheaper to fix, cheaper to replace. For Amazon sellers, that lower return cost often matters more than the lower unit price.

Certifications and Market Fit

CE and RoHS are baseline for EU. UKCA for the UK. ERP compliance covers standby power and thermostat accuracy — non-negotiable if you're selling into Germany or France. For bathroom models, you need IP24 at minimum. Don't let a supplier tell you IP21 is fine. It isn't.

A wifi smart electric heater adds maybe $4–6 to your BOM but lets you charge $20–30 more at retail. The app development is usually shared across SKUs, so the marginal cost drops fast. If you're building a private label electric heater line, start with a wifi convection panel and a non-wifi oil filled radiator. That covers both buyer types without doubling your tooling.

Which One Should You Stock?

If your customers are renters, students, or small apartment dwellers: convection. Fast heat, lower price, lighter shipping.

If your customers are homeowners, older buyers, or anyone who complains about fan noise: oil filled. Silent electric heater searches are real and growing. Oil filled owns that space.

If you're selling into workshops or garages: neither. Go industrial fan heater. Different product, different conversation.

A practical split for a first container: 60% convection, 40% oil filled. Adjust after one season of sell-through data.

One Honest Takeaway

The oil filled vs convection decision isn't about which heats better. Both heat. It's about which one matches your buyer's patience and your return budget. Convection is cheaper to make and cheaper to replace. Oil filled commands a higher retail price but demands tighter quality control. Pick based on your market's tolerance for waiting, not on spec sheets.