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  • Bill Kinney

Gas? Or Electric?

With the popularization of electric induction cooking on land, a similar trend has been going on in the boating world. Electric induction cooking is becoming more popular, and it is definitely the “in thing” to do. But does it make sense to convert an existing boat galley from propane (or as is more common in Europe, butane) to all electric? Let’s look at things…


Cooking

Electric induction cooking has been around for years, but has only recently taken hold in a major way. The stove top “induces” tiny electric currents to flow in the metal of the pan, and this rapidly heats the pan. When you are cooking with an inductive stovetop, the heat is immediately responsive, it gets hotter and cooler with no lag when you turn the dial. From a cooking perspective, they are infinitely superior to traditional electric cooking using a resistance element.


You can probably start many a fight to the death among serious cooks trying to decide if inductive cooking is better, equal, or inferior to a proper gas stove top. Let’s leave that to the cooking nerds for now and say they are roughly equivalent.


For stove top cooking, an induction cooker is much better than a traditional electric cooker, however there are no “induction ovens.” Electric ovens are all simply resistance heaters. In theory, a sophisticated control system could control an electric oven’s temperature more precisely than a similar gas oven. In the real world, very few small ovens have such a control system, and the temperature control in gas or electric is not significantly different. In the typical boat oven, I am going to call this also a tie.


In all cases here I am assuming that reasonably high end equipment is being used. Certainly there are both gas and electric cooking equipment on the market that are, shall we say, "crap."


Safety

The first, and for many people, the last and only, argument for switching to electric cooking is safety. Certainly the boating community is well aware of the potential hazards of propane. A propane leak in a boat can lead to a violent explosion and fire. The things that need to be done to have a safe propane installation are well known and (usually) carefully followed because people are hyperaware of the issue.


When we look at actual claims data for fires onboard boats published by BoatUS/Geico, we see the following breakdown:

  • 37% DC Electrical System

  • 9% AC Electrical System

  • 19% Engine

  • 14% Fuel

  • 12% Other

  • 9% Unknown

This tells us a very different story than we might expect. Notice that propane does not even appear on the list, but is buried down in the “Other”category. What we see is that the electrical system onboard is statistically MUCH more dangerous. Especially the kind of high amperage DC supply that is needed to power an inverter capable of running galley cooking equipment. Propane turns out to have a very low rate of accidental fire on boats BECAUSE people are so scared of it, and take such care with it.


The conclusion from this is NOT that electrical systems are inherently more dangerous than propane, but something a bit more subtle. BOTH systems can burn your boat down and kill you in the process. Both systems when installed and maintained properly are safe. We incorrectly assume that 12 or 24 volt systems are somehow “intrinsically safe.” Actual data on the cause of boat fires shows us this is a very bad assumption to make.


Power Needs

An important point to remember: Electric cookers do not modulate their power needs, rather they are all controlled by turning themselves ON/OFF as needed. Set your 1800 Watt induction burner to 50% and it is not drawing a steady 900 Watts, but rather it is pulling 1800 Watts half the time. The consequences of this are very important for your electrical supply.


If you are cooking a complex meal and using three 1800 watt burners, and the oven rated at 1200 Watts, your electrical system needs to be able to supply: (3 * 1800) + 1200 = 6600 Watts because at some point in time all four heating elements might be on and drawing their full rated power, even if each one is turned to a very low setting. 6600 Watts is 55 Amps at 120 Volts, or 30 Amps at 220 Volts. This is beyond the capability of a 120V/50A shore power supply and right on the edge of a 220V/32A shore power connection, even if nothing else on the boat is running.


At least one of the very high end marine cookers is made by a company that recognizes this problem, and the equipment has circuitry to limit the total power draw, but even these need a power supply of 5000 Watts.


Of course, most boats that install induction cooking are hoping to run it off batteries, which means that DC power is being used to run an inverter, to make AC power to actually run the cooker. 6600 Watts is 275 Amps at 24 volts, and 550 Amps at 12 volts. This is a LOT. These kinds of very high power DC systems need to be installed and maintained very carefully. Something as simple as a single loose connection can generate enough heat to start a fire.


Just generating this much AC power requires larger inverters than most boats less than 65 feet or so would have installed. Either a major redo of the electric system would be needed, or running the generator to cook.


Fuel Availability and Cost

The following cost analysis is admittedly very rough. Total costs for energy are hard to pin down, and vary a lot from one locality to another, not to mention these costs change quickly over time. I think the differences are large enough that the conclusions would hold up pretty much anywhere. We do not need a really sharp pencil to see what the trends are.


We carry three 10 pound propane tanks. Each of those tanks lasts about 2 months of normal daily cooking. We have never been anywhere that propane was so difficult to find we were down to using our last tank. We have found propane to be very inexpensive—a rounding error in our total cruising budget. About $50 to fill all three tanks. So roughly $8.30 a month. Kind of down the line about even with toothpaste...


For most boats, it is a bit of a pipe dream to have solar panels supply enough power to run electric cooking. Some catamarans have enough surface area that they can reach this target, but it is a very expensive project! Everybody else is using a generator to produce the the extra energy needed.


Here is a very dirty secret: Generator supplied electricity on a boat is EXTREMELY expensive. Our generator, when operating at full load (its most efficient setting), makes about 5.5kW-hours per gallon of fuel burned. So a kW-hr of energy costs almost a dollar, just in fuel. Add in maintenance and depreciation, and the total costs for a kW-hr of energy are pushing $2. That’s about 15 times the average retail cost of grid power in the US. Our generator was specified and designed to run at close to full load almost all the time. Most marine generators run at far lower average load, and will therefore consume a lot more fuel per kW-hr produced.


Our daily fuel use (WITHOUT cooking) for power generation is about 0.5 gallons, maybe a bit less. We carry about 150 gallons of diesel fuel, or about 10 months of supply if we only ran the generator, and never used the main engine. I would estimate our electrical power needs would roughly double if we used 100% electric cooking. So electric cooking would cause our fuel use to double and add roughly half a gallon a day of fuel to our current usage, or 15 gallons a month. At current prices for marine diesel this is about $75 a month. Almost 10 times as expensive as using propane, and that’s NOT counting the maintenance and depreciation costs of the generator.


But! But! But! SOLAR!!!!!

Yep. There is that. We have 630W of solar installed on our boat that supplies about 1/2 of our total power needs (excepting the watermaker). This is about all we can fit in ways that I am comfortable mounting. Every once in a while, I revisit the costs of adding solar and seeing if it makes sense.


Because of mounting limitations, we are limited to some of the more expensive solar options, flexible and semi-flexible panels. To double our solar capacity, and significantly reduce our generator run time is not at all cheap. For good quality panels about $6/Watt. To double our capacity would be 630 *6=$3800 + installation materials and costs.

Note, that's STILL not enough for us to cook electrically with solar, just run our current systems (NOT including the watermaker)! $3800 buys an AWFUL lot of diesel fuel. More than 3 years worth at $6/gallon.


So The Answer Is…

It might read like I am totally opposed to electric cooking. I am not. We have an electric oven on board that gets regular use in addition to our propane one. I boil water every morning for my coffee using an electric kettle. Modern induction cooking is very slick. It doesn’t add a lot of excess heat to the boat cabin. It is clean. I have used an induction hotplate, and they are totally awesome. For some kinds of cooking they are better than gas burners. Such an induction hotplate is on our list of purchases to be made when we are next in a place where 220V appliances are readily available. I would never say anybody was wrong if they wanted to cook only that way.


Just don't do it because someone tells you it is "safer." There is no evidence that it is. And CERTAINLY don't do it because someone tells you it is "cheaper." It is absolutely NOT.

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