Domestic Fridge/Freezer Size Considerations

Firstly, has your narrowboat got adequate room to house a domestic under counter fridge and/or freezer? The standard size of a 230v under counter fridge / freezer is approximately 850mm high x 550mm wide x 600mm deep. This is particularly important if you’re looking to replace a narrowboat fridge / freezer or if considering galley layout and counter depth.

There are of course other alternatives to an under the counter freezer, such as a chest freezers.

Running a Domestic Fridge or Freezer off an Inverter

The market for new narrowboats is rapidly moving towards a home from home type familiarity, almost all new narrow boats are installed with inverters more than capable of running a domestic fridges / freezers.

To consider running a 230v fridge / freezer whilst away from a 230v hook up / shore power you will need to generate the power from the 12v battery bank via an inverter. Whenever the fridge / freezer is on so will the inverter, so the reliance will be on two appliances for your refrigeration not one.

Domestic Fridge / Freezer Price Benefits

Well immediately on face value the 230v appliances are much cheaper average price around £150 inc VAT and depending on where you make your purchase guarantees of 2 years can come as standard, with the option to add a further 3yrs for around £35.00.

Domestic Fridge Power Consumption (Watts/Amps)

For the purposes of this example we will use a 230v fridge. A freezer would produce a similar set of figures for comparison.

Well let’s try an make this simple. Firstly lets summerise the developments in fridge economy over the last 5 years …..Since 2010 to 2016 energy consumption has been reduced by nearly 70%, making a fridge a much more appealing proposition for canal boats and narrowboats.

At the time of writing this guide 230v fridges are generally certified A+ rated so let’s work with this. The average energy consumption of a 230v fridge is quoted as 169kWh per year so how can we translate this for calculating the impact on a canal boat or narrowboat 12v battery bank?

• We need to x1000 to convert to watts and then divide by the amount of hours in a year (365×24) which equals 8760. So 169×1000/8760= 19.29 Watts per hour.
• We now need to make this relevant to the hourly amp hour draw on your battery bank. Which is watts divided by volts or 19.29/12= 1.6amp/hrs.
• Finally we need to factor in the energy efficiency loss generating the power for the fridge through an inverter for this we add 20%, 1.6×1.2=1.92amp/hrs.

This is very interesting as a leading 12v fridge manufacturer quotes power consumption between 2.2 – 2.5 amp/hrs that’s 14% higher power draw than a standard 230v A+ rated fridge!!

• 230v domestic A+ rated fridge amp usage per day = 46amps
• 12v marine fridge amp usage per day = 52.8amps

However… Do you need to factor in the inverter being on 24/7? This is really important… How do you, or will you use your inverter? Or let me ask this question another way… Forget the fridge for a minute, do you want 230v on demand i.e do you want to plug a mains powered device in, turn the socket on and have power? If the answer is yes then you don’t need to factor in the power draw of the inverter as it will be permanently on anyway. If the answer was no, then you will perhaps be turning the inverter on as and when you require power. If this is the case then you should factor in the power draw of an inverter being on, and this makes all the difference.

Average inverter power draw is 1.2amps per hour or 28.8amps a day when switched on. Now let’s re-evaluate the comparison…

• 230v fridge amp usage per day = 74.8amps
• 12v fridge amp usage per day = 52.8amps

This is a game changer as now a domestic fridge draws over 40% more power than a 12v marine fridge. A massive difference hence why we posed the question should you consider this in the calculation.

Battery Cut Off/Protection when Running a Domestic Fridge or Freezer

Assuming you are investing in a inverter fit for purpose to run a fridge / freezer 24/7 if required, the inverter will have a low voltage warning alarm and a low voltage cut off to protect against heavy battery power discharge which can dramatically reduce the life of a battery bank.

12v Fridge / Freezer Size Considerations

Well this is where a significant amount of choices are available in comparison to the standard household fridges / freezers. This can be a decision maker in its self. If replacing a gas fridge for example there are direct size replacements in the 12v marine fridge market.

Also depending on the capacity you require a standard size fridge may well be too big for your needs and a smaller more energy efficient option could be more beneficial.

• Freezer capacity ranges from 34 – 109 litres
• Fridge capacity ranges from 40 -142 litres

12v Portable Fridges for Narrowboats

A portable fridge is also an option to consider, particularly if you only use your canal boat or narrowboat occasionally. The fridge can then be used for other purposes away from the boat e.g a secondary fridge at home or camping trips.
A variety of sizes are available up to 65 litre capacity.

A visit to any camping store will demonstrate the variety of equipment available, in terms of type. size and price. You can of course opt for a traditional insulated cool box/bag however these only keep items cool with ice blocks so are very time limited and probably only suitable for a day’s cruising, but require no electrical input. Thermoelectric cool boxes are similar to the above but with the addition of an electric fan which can be powered using 12v. How cool these keep your food is dependent on the outside temperature, so again a short term solution. A compressor coolbox (or fridge) is the better option for longer term use. You can set the temperature for your food or even freeze it and it is unaffected by the ambient temperature. These are powered through 12v.

Price Disadvantage of 12v Fridges or Freezers

Well this is not a plus point 12v fridges / freezers on average cost around £600, four times the price of a household fridge / freezer.

12v Fridge / Freezer Power Consumption (Watts/Amps)

Well before we looked seriously at 230v v’s 12v fridges, one of the main assumptions we had was 12v marine fridges would consume less power than their 230v equivalents. Since making the calculations on similar sized fridges surprisingly with today’s energy conscious consumers and manufacturers this assumption is now a myth. In fact on paper it seems a like for like sized 12v marine fridge may consume up to 14% more power. The difference comes if you factor in the power draw of an inverter being on 24/7 as mentioned above if you do this a 12v fridge is consumes 40% less than a 230v domestic fridge… So a very important question is would you always run inverter in the background anyway whether you had a 230v or 12v fridge? If yes I think you can run with the opinion that a 230v fridge is more efficient.

What power benefits are there then? Well first and foremost running a 12v fridge removes the continuous need to run an inverter or even own or install one in the first place. Many traditional boaters rely on 230v power as little as possible and might not install an inverter and perhaps just have a generator for essential running of 230v appliances like washing machines.

However, today’s boater favors a home from home environment with high end inverters (units which input 12/24v and output 230v) which aren’t cheap, many installed on today’s canal boats / narrowboats run in excess of £2000.

Removing the demands of running a 230v fridge 24/7 via an inverter may arguably reduce wear and increase the life span of an inverter? It will also remove the reliance of continuous inverter operation. It is not uncommon for inverters to shut down on occasion due to temperature overload, more common on hot summer days, and can leave you short of electric for an hour or two. If the inverter develops a fault or stops working so does your fridge, opting for a 12v marine fridge with a direct link to the leisure batteries will avoid this problem all together.

12v Battery Powered Fridge Installation Tip!

For 12v marine fridge installations to ensure power efficiency and avoid volt drop it is essential you specify the wiring correctly in relation to the cable length to the battery bank.