Campervan vs House Heating Comparison
It’s freezing outside, don’t you get cold? I get this question a lot. Not to worry, I have a 6 kilowatt Webasto diesel heater installed so my Sprinter stays nice and toasty. It’s sized for larger vehicles, and can easily keep my fairly well insulated campervan as warm as I desire, even when it’s below zero outside. Really, I measured the hot air coming out of the vent at a toasty 216 deg F! But I usually keep it around a reasonable 50 degrees inside the van so I’m not wasting excessive energy.
Hot air outlet. Carrie hooked me up with a thermal camera to have some fun with… cause we’re nerds.
I was having a discussion with my friend Mike recently about how much the heater runs and how well insulated the van is. I pointed out that it almost certainly takes more energy to heat his house than it does to heat my van, as the van is so much smaller. I wasn’t totally sure though, and this got me thinking. How much energy am I actually using for heat, and how much is it costing me? How does that compare to a typical home? Putting my engineering background to some good use sounded fun, so follow along to indulge your inner nerd.
First question, how much fuel do I use?
This is my biggest uncertainty in this analysis. My gut feel from watching the fuel gage is that on the cold days we’ve had recently (around zero F), I’ll use ballpark 1/16 of a tank of fuel in a day to keep the van heated. My tank holds about 25 gallons, so that’s 1.56 gal/day. This is very much a guess though.
I looked at this from another angle to corroborate this number. The spec fuel consumption rate for the heater ranges from 0.19-0.66 l/h. Using some rough estimates that my heater typically runs at about 50% power (.43 l/h), and 40% duty cycle (meaning it’s running 40% of the time, or 9.6 hours out of the day) when it’s this cold out, I get the following:
Close-ish. I’m just going to split the difference and assume a use of 1.32 gal/day.
It’s been cold this year, the Webasto Dual Top has gotten a workout.
How much energy is this?
Thinking back to my days working with combustion engines, the Lower Heating Value of diesel should probably be about accurate for how much usable energy the fuel produces (now this is getting fun). A standard value for this looks to be 36 MJ/l.
And to placate an old boss who always insisted I give him values in units he could relate to:
Great. This probably doesn’t mean a lot at first glance, but don’t worry, we’ll make sense of it later.
Note the cold rear doors and ribs on the ceiling.
So how much does this cost me?
Diesel fuel right now is around $2.90/gal, so:
That seems pretty reasonable. But it makes me wonder how much of this cost is specific to the fuel, and how it would change if I’d installed, say, a propane heater. Looking at the cost per energy content of different fuels provides an easy way to compare this. Here are the calculations for diesel:
The national average for residential propane is currently about $2.50/gal, but if you’re refilling smaller tanks (automotive style) it looks like the cost is more like $4/gal so that’s what we’ll use. We need the Lower Heating Value here as well, which is 24.4 MJ/l.
I also looked at some other common fuels and ranked them all according to cost.
Fuel energy comparison, and costs for van at zero deg F
It’s interesting to see how much more expensive propane is than the other fuels, at least when buying in small quantities. Further, if I had installed a propane heater instead of diesel, I’d barely get over two days of serious heating from a standard 20 lb propane tank (disregarding any efficiency differences, and assuming the energy use I calculated above)! A 20 lb tank holds about 4.7 gallons of propane. We can figure out how much energy this is, then use my daily energy requirement from above to calculate how long this will last in zero degree temps.
I had no idea propane was that expensive, or that you needed so much of it compared to other fuels! I chose the diesel heater primarily because I didn’t want the hassle of a second fuel, but now I have two more good reasons.
Frost inside the windows is just a reality in winter, no matter how good the insulation or heater.
House Analysis
So, now that we have a good idea of the energy use and cost for an insulated Sprinter campervan, let’s see what typical energy consumption is for a house. Mike and I were able to pull up historical data for his 2600 square foot house in Wisconsin, and found that his highest recent usage was 180 Therms over a month with 1286 heating degree-days. His place was built in the 50’s and is reasonably well insulated, so it should be a good representation of a typical house.
Degree-days are a measure of how cold it is for how long, and are used to normalize energy use across different climates. They’re typically stated with a base temperature of 65 F, which, for simplicity, we’ll assume is the interior temp. Since Mike and Carrie are reasonable people concerned with their energy use, they keep their house more like 60 F. When we adjust for this we come up with 1131 degree-days for their specific house over that month (which would equate to an average outside temp of 24 deg F). This means we can do some simple math to figure out roughly how much energy their house will use at a given exterior temperature.
Since it’s been around 0 F recently and that’s what I’m basing my van heating case on, we’ll use that same temperature to evaluate Mike’s house. With a base temp of 60 F and an exterior temp of 0 F, we end up with a 60 deg difference.
Comparing that to my van energy use of 1.7 Therms/day, we see that Mike’s house uses over five times the energy to heat as my van does on the same day. Woohoo, I do use less! Although for a fair comparison, we’ll need to do the degree-day adjustment for my van as well to account for the lower temperature I keep it at.
Since I usually set the Webasto Dual Top thermostat to about 50 degrees, and the exterior temp we based my energy use on is around zero, the temp difference is 50 deg. So getting a temperature-specific number looks like this:
If I were to keep the van at 60 deg like Mike’s house, I’d use about 2.05 Therms/day. Therefore my energy use is really closer to a quarter of Mike’s.
However, Mike quickly pointed out that he has approximately thirty times more square feet than I do, and when you look at it that way I’m using over six times the energy per square foot! This isn’t too surprising considering how difficult it is to effectively insulate a vehicle made of metal ribs and single-pane glass.
The weak spots are definitely the doors and windows.
House Costs
Finally, let’s look at the cost for Mike’s house.
For comparison sake, it would cost me $4.59 to keep my Sprinter at the same 60 deg interior temp as Mike’s house on the same zero degree day. So, even with Mike using economical Natural Gas, it’s still quite a bit cheaper overall for me to heat the Sprinter with Diesel than for him to heat his house with NG. Vanlife wins again!
Obviously when we look at any of these measures on a space basis, a house is far more efficient than a van. That said, I’m glad to see that it at least costs me less than half of what it costs to heat a normal house.
I feel like my Sprinter is fairly well insulated, and short of spray-foaming the entire thing, there aren’t many changes I can think of that would be significant improvements. The thermal images show that the weak spots are the doors and large structural metal areas, and there isn’t a whole lot you can do about that. Maybe replacing all the weatherstripping would help, but I doubt it would be cost effective. Vehicles made of sheet metal and single-pane glass just aren’t designed to be insulated efficiently.
These screw heads are routinely covered in frost.
One thing I was quite happy to see was that my curtains appear to be pretty effective. They’re made with a layer of decorative fabric on the front, a radiant barrier fabric on the rear, and are secured pretty tightly to the ribs around the windows via sewn in magnets. I highly recommend this method!
I’ve been pretty happy with the performance from the Webasto diesel heater, and am glad to see that it’s not costing me an exorbitant amount to keep it running. The van is able to handle sub-zero temperatures without many problems, which is great for trips to the ski resorts or just hanging around Wisconsin in January… because why wouldn’t you want to do that? While it’s awesome to have the capability to withstand Wisconsin winters, I fully intend to use my home’s self-propelled feature soon to get me to a warmer place where keeping the van heated isn’t a concern.
*Note: I made a number of assumptions and simplifications in this analysis, including omitting efficiency differences between different style heaters and combustion. These are just rough calculations to give an overall idea of energy consumption and how the van stacks up to a traditional house.
Degree days and BTU’s takes me back to my old days at Wisconsin Gas.
All this makes me go brrr and I say you need to come visit AZ again soon!
Yeah Karla, you guys definitely have the weather advantage this time of year! Maybe I’ll make it down there before too long. I’m sure not coming during the summer though 😉
Impressive! Thank you for doing the detailed analysis so I can point people to this post to explain how my long distance van road trips aren’t single-handedly causing climate change.
It is surprising that propane is more expensive per day given that it doesn’t include highway taxes. It’s also surprising how often it needs to be refilled. Burning propane releases a lot of water vapor, and that causes issues with condensation (and interior frost!) in the winter. Being able to camp out at a ski resort for 3 days in a snowstorm is a big advantage of using Diesel for heating and driving.
It’s surprising that your heat vent is nearly boiling although if the duct is small that might focus the heat. I got the Espar D4 (13kW) instead of the D2 because I have the longer Sprinter and I had read that the D4 uses less electricity in the low mode. The problem is that my D4 is so efficient at moving air (with an 8cm duct diameter) that it heats the entire van up, shuts off, and then has to go through the louder boost cycle. The D2 would probably need to stay on throughout the night, so the extra cost of the D4 wasn’t worth it. It also doesn’t seem to turn back on normally if I set the thermostat for less than 67 F, so that’s what I use. Definitely not the most efficient temperature when it is 0F outside…
While I don’t mind camping in the snow before a ski trip, it is nice to camp in places where it is warm enough to avoid running the heater at night.
Have you tried one of the 12v electrical mattress heater? I bought one and it seems too hot even on the lowest setting. But it is useful for stealth camping in neighborhoods where running the Diesel heater would make some noise.
Haha, yes it does probably seem on the surface like driving every day might be worse than living in a house as far as CO2 emissions and impact. I’m guessing it’s still a lower overall environmental impact, but don’t really have a feel for how it compares. That’s another analysis I’ve been thinking of doing for a while, but haven’t found the motivation for that one yet.
I was pretty surprised at how propane came out too. I need to find someone with a propane heater and see how their use compares to this.
That sounds like a really annoying problem with your D4, I’d definitely get that checked out.
I’ve never tried an electric pad, good tip. Not sure how much power those draw, but I do try to limit big electrical loads. I’d also say the heater is a lot more important for overall comfort hanging out in the van than it is for sleeping.
Yes, the Diesel air heaters are key for making #vanlife enjoyable in cold temperatures. Graphite Dave Orton on the Sprinter forum swears by his Electrowarmth heating pad but he didn’t install a Diesel air heater in his Sprinter or Transit and he lives in coastal California where it doesn’t get that cold. I’ve used the heater duct of my Espar D4 to thaw my feet after a bike ride near Mammoth Lakes where it was snowing in June so I definitely think a Diesel air heater is necessary for high altitude camping, biking and skiing, especially in winter.
I only used the heating pad once or twice last winter but it was only covered by a sheet so I felt the heating wires each night for the winter whole trip. I took it off before the Alaska trip and was happy to not sleep on wires. This time I put it under a slightly cushioned mattress cover so I won’t feel the wires and it will help dissipate the heat when it is on. Even the lowest setting (which apparently uses 1.5 Amps DC) was too hot. I’ll report back if it is more comfortable.
This is AWESOME. Well played, sir. I’ve always wanted to calculate this and blog about it, but now I can just point people to your post! Engineering FTW. Keep on living your dream!
Glad you appreciate it Dakota! It’s fun to do these kind of quick ballpark calcs to see how vanlife stacks up. I’d love to do a full energy analysis of my life in the van vs a house, but that sounds pretty complicated and I haven’t quite gotten the motivation yet. Thanks!