What Size Diesel Heater Do You Need?
Key takeaways
Most Webasto, Espar, & Chinese diesel heaters produce more than enough heat to adequately heat a van…
But if you’re wondering exactly what size you need, or if a larger heater would be better, keep reading.
Related: Best Diesel Heaters for Van Life
How to Calculate How Much Heat You Need
To calculate how much heat you need for your van, just multiply the square footage of your vehicles living space by 20 BTU’s.
20 BTU’s (or British Thermal Units) is the standard measure of heat output recommended per cubic ft of space used in home heating and air.
Formula for Calculating Heat Needs:
(Length x Width x Height of Living Space) x (20 BTU’s)
As you can see from the table below, most reasonably sized vans will stay adequately heated with 3,000-12,000 BTU’s (assuming your floor, ceiling, and walls are well insulated). If you’ve converted a school bus or box truck camper or something larger, just use the calculation to check the cubic footage.
| Vehicle | Length | Width | Height | Cubic ft | BTU’s |
| Sprinter 170 Ext | 15.75 ft | 5.83 ft | 6.58 ft | 604.19 ft³ | 12,083 |
| Ram ProMaster 159 | 12 ft | 6.25 ft | 6.41 ft | 480.75 ft³ | 9,615 |
| Ford E-Series | 10.11 ft | 6.13 ft | 4.49 ft | 278.41 ft³ | 5,568 |
| VW Van | 8.85 ft | 4.925 ft | 4.42 ft | 192.65 ft³ | 3,853 |
| Dodge Caravan | 7.29 ft | 5.16 ft | 5.08 ft | 191.09 ft³ | 3,821 |
| Chevy Astro | 10.5 ft | 4.65 ft | 3.90 ft | 190.41 ft³ | 3,808 |
| Ford Transit Connect | 9.79 ft | 4.05 ft | 4.12 ft | 163.35 ft³ | 3,267 |
Webasto, Espar, and Vevor all provide diesel heaters that produce over 12,000 BTU’s.
Related: Diesel Heater Installation Cost
| Heater | Max BTU Output | Source |
| Webasto Air Top 2000 STC | 7,000 BTU/h | Product Manual |
| Espar Airtronic S3 Commercial D2L | 7,506 BTU/h | Product Manual |
| Vevor 3KW Diesel Air Heater | 10,236 BTU/h | Product Manual |
| Webasto Air Top Evo 40 | 12,000 BTU/h | Product Manual |
| Espar Airtronic M3 Commercial D4L | 13,648 BTU/h | Product Manual |
| Espar Airtronic M3 Recreational D4R | 13,648 BTU/h | Product Manual |
| Vevor 5KW Diesel Air Heater | 17,060 BTU/h | Product Manual |
| Webasto Air Top Evo 50 | 17,000 BTU/h | Product Manual |
| Espar Airtronic L3 Commercial D6L | 20,472 BTU/h | Product Manual |
| Vevor 8KW Diesel Air Heater | 27,297 BTU/h | Product Manual |
| Espar Airtronic XL3 Commercial D8L | 27,297 BTU/h | Product Manual |
Is it Better to Have a Bigger Heater?
Larger heaters produce more heat, but as long as your minimum capacity is met, more BTUs just gets you warm faster.
| Heater | Max Output | Time to 12,000 BTU |
| Vevor 8KW Diesel Air Heater | 27,297 BTU/h | 26 Minutes |
| Espar Airtronic XL3 Commercial D8L | 27,297 BTU/h | 26 Minutes |
| Espar Airtronic L3 Commercial D6L | 20,472 BTU/h | 35 Minutes |
| Webasto Air Top Evo 50 | 17,000 BTU/h | 42 Minutes |
| Vevor 5KW Diesel Air Heater | 17,060 BTU/h | 42 Minutes |
| Espar Airtronic M3 Commercial D4L | 13,648 BTU/h | 52 Minutes |
| Espar Airtronic M3 Recreational D4R | 13,648 BTU/h | 52 Minutes |
| Webasto Air Top Evo 40 | 12,000 BTU/h | 60 Minutes |
| Vevor 3KW Diesel Air Heater | 10,236 BTU/h | 70 Minutes |
| Espar Airtronic S3 Commercial D2L | 7,506 BTU/h | 95 Minutes |
| Webasto Air Top 2000 STC | 7,000 BTU/h | 102 Minutes |
Are Larger Heaters More Efficient?
Its difficult to calculate the fuel consumption of each heater at a specific BTU output, but manufacturers state the minimum and maximum fuel consumptions, and the differences are stark.
| Heater | Max BTU/h | gal/h | Cost Per 24 Hours |
|---|---|---|---|
| Espar Airtronic XL3 Commercial D8L | 27,297 | 0.25 | $24 |
| Espar Airtronic L3 Commercial D6L | 20,472 | 0.19 | $18.24 |
| Webasto Air Top Evo 50 | 17,000 | 0.16 | $15.36 |
| Vevor 5KW Diesel Air Heater | 17,060 | 0.13 | $12.48 |
| Webasto Air Top Evo 40 | 12,000 | 0.11 | $10.56 |
| Espar Airtronic M3 Commercial D4L | 13,648 | 0.12 | $11.52 |
| Espar Airtronic M3 Recreational D4R | 13,648 | 0.12 | $11.52 |
| Vevor 8KW Diesel Air Heater | 27,297 | 0.13 | $12.48 |
| Espar Airtronic S3 Commercial D2L | 7,506 | 0.07 | $6.72 |
| Vevor 3KW Diesel Air Heater | 10,236 | 0.09 | $8.64 |
| Webasto Air Top 2000 STC | 7,000 | 0.06 | $5.76 |
What Size Diesel Heater Should You Buy?
Considering all of this… The right size diesel heater is the one that produces enough BTUs to cover your vehicles heating requirements based on this formula:
(Length x Width x Height of Living Space) x (20 BTU’s)
If you’ve got that, you can be confident that whichever size diesel heater you choose will provide you with more than enough heat.
