The Offshore Voyaging Reference Site

Q&A: Is The Espar Heater Really That Hot?

Question: My experience with diesel heat is that it’s hard to light, hard to control, it smells and the deck is covered in soot. That was 25 years ago with the stainless steel pot belly stove in [a] Westsail. You rave about the Espar diesel heater. Is the Espar really that good and does it address my previous experience with diesel heat?

Answer: Yes, the Espar (Eberspaecher) really is that good. Our Espar D8 has run for about 4000 hours and has never let us down. Very occasionally, as it fires up, we get a slight whiff of diesel but that clears as soon as it completes the ignition cycle.

The key issues are good installation and to make sure you have it serviced at least once every two years. (If you are mechanically inclined and can pry the service manual out of the dealer’s hands, you can learn to do this yourself.) Also, you should make sure you run it regularly (not a problem for us).

On the installation, it is vital that the power cables are heavy enough and that you follow the instructions for the fuel pickup and fuel pump installation to the letter. Mess up in either of these areas and the thing will drive you crazy. Also, see our comments and photograph on a proper exhaust for an offshore boat.

If you will be far from service help, it is probably worthwhile investing in one of the little black boxes that allow you to read diagnostic codes and reset errors on the Espar, as well as a few spare parts including a glow plug. Also, keep in mind that on the air units the blower motors only last 2000 to 3000 hours. We carry a spare.

Having said all that, if we were to do it again with what we know now and keeping in mind our heavy usage, we would have installed a water, rather than air, circulation unit from Espar or possibly a Refleks from Denmark. The advantage of the Refleks is that it is a much less complex machine than the Espar and uses no electricity (the Espar is a power hog). The advantage of the Espar is automation: Need heat? Flick a switch and you got heat.

The disadvantage with both water circulation solutions is that they are more complex to install than the air unit we have. Also the Refleks requires a real chimney, rather than the simple exhaust of the Espar, and with a water coil to feed the radiators, which we would need to heat our aft cabin, which is very large.

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Neil McCubbin

Our experience with Espar
We installed a 5 kW air unit while finishing the interior of 47 foot Milvina in Quebec, outdoors. It keeps the interior about 20 deg C above the outdoors, unless the wind is really howling.
Used a lot for 3 winters.
Since we do not sail when the weather is below zero, that is plenty of heat.
While sailing, it warms us up, and more importantly dries out the interior very well. The 4 amps while running is of course a nuisance, but we do not normally run for more than an hour or so.
We had 3 years in south with zero use, and 3 in cool climates with about 30 hours/year use.
The key problem is reliability.
It has failed to start twice. Each time back to the shop (luckily there was a service shop nearby both times). In each case the only trouble was that the controller needed resetting. This requires special gadgets.
Both repairs took only a few minutes once diagnosed, but cost us a few hours to remove the heater and a charge of about 80 Euros.
Had the failures happened in a remote location, the inconvenience would have been major.
I find it infuriating that Espar designs a system that can shut off and prohibit restart due to some minor glitch.
Does anybody have a solution?
I am glad we have the air unit rather than water, because by pulling in outdoor air and heating it, the boat dries out quickly.
We have an outlet in the foul weather gear locker that dries stuff well.

Ed Seling

Back in the late 80’s I spent 4-5 years with an Espar DL 1 (Their smaller unit). I put up with it because I felt it safe to leave on at a low setting while I was at work but I did not like it at all. On the coldest days it would either not start, the blower would seize up, the pump would not function, or any of a number of other things.

When we got our 41ft. “Moonshadow” I installed two Sigmar (now Force 10) diesel heaters, one in the main cabin and one in the aft. One does the job in almost all weathers though in Newfoundland we occasionally needed two.

They gravity feed off a day tank and need no electricity other than two small fans to keep the cabin heat from stratifying. They are easy to light, offer a cheery flame, and if properly adjusted give off little smell or smoke. Sometimes I fail at this and there is a bit of soot around the chimney on deck but a quick wipe with a soapy rag takes care of that. Once a year I clean out the burners and while a dirty job it does not take long.

They take in combustion air from the outside using a balanced draft system which makes them virtually immune to blow backs in the windiest weather. Gusts of 70 kts and more, such as we had in winter Newfoundland, and our flame only danced a bit and never blew out.

They do require a stack which interferes with sailing and the carburetors prefer to be fairly level but we are not really cold weather sailors so it is not a problem for us. Push comes to shove, we have engine heat.

We have been with these heaters for about 15 years now and could not be happier.


wild bill

We have the small espars in equipment where I work and have found they were virtually trouble free once we started using kerosene instead of diesel. Much cleaner combustion and other than the occasional blower motor reliable.

Terry M. Day, Jr

One company that I worked for used Espar heaters in their trucks for heating. I found they were glitchy when they did work and temperature was hard to control.

I would be very reluctant to recommend Espar to anyone. As for smell, I never noticed a diesel smell. They do burn clear and leave no “soot”. They smoke a white cloud out the exhaust when first start then go clear.

Again, I have no experience with the Marine version, but the truck versions were unreliable and expensive to fix.


Espars being unreliable is a bunch of BS. I’ve used them for 25 years in a series of boats in Canada (where we know what cold is). The first one a D1 (600btu), second one a D3 (11,000btu), third and fourth ones A4 (12,000btu). If you install them properly and use them properly they are bullet proof reliable. As mentioned pay close attention to the fuel system installation as per the manual and use heavy power connection wiring (since the glow plug runs for approx. 1 minute at start-up and draws big amps). The biggest mistake I see people make when operating their Espar is not utilizing the proper shut-down technique EVERY time you turn the unit off. The technique is to run the unit on high for a few minutes to make sure the glow plug is hot and clean then use the Espar’s switch on the thermostat to turn the unit off. If you simply cut power to the Espar to shut it down without going through its shutdown sequence you will have nothing but problems.
Espars are very “smart” devices with a built in microprocessor that checks several things like supply of diesel being rec’d, clear exhaust pipe, availability of combustion air, etc. Upon sensing problems in any of these (plus some more) areas the unit will not run and instead display an error code.
There is nothing quite like turning a switch on, dialing in a temperature then relaxing in your cabin or berth while its cold outside. The posting above Terry M Day mentions a poor experience at heat regulation in trucks which is likely because most truck installs don’t use the thermostat to regulate heat (often they just have a much simpler timer based control to run the unit for a while at full then shut down).
Bob W

Jim R.

I have an Espar air heater (D5L I think) in my new to me boat. It has not worked since purchase. Any advice on service for it between North Carolina and Florida?