Choosing the right inverter for your boat

Date posted: 24 October 2015

Having an inverter on board your boat allows you the pleasure of using luxury electrical gadgets such as televisions, printers, microwaves and dare I say it hair dryers! Inverters are also essential for recharging the more important items on board such as your hand held VHF batteries, phones, ipads and electric tools. Inverters simply and silently convert 12V DC battery power to 230V AC electricity – for operating mains powered devices when you don’t have access to grid power.

Before you go out and buy an inverter there are a number of factors to consider. Depending on your requirements once away from the pontoon, I would recommend you keep both a generator and an inverter on-board because they complement each other.

I’m pretty confident that I’m not the only sailor, that has run boat batteries down to zero on an overnight sailing trip; leaving the radar on! (School boy error I know – I learnt from that mistake). This is just one example of why having a generator on board is exceptionally useful. (There will be a November blog article on generators).

Let’s get back to inverters; inverters either produce a true sine wave or a modified sine wave. The true sine wave inverter being more efficient and expensive, but will run your equipment such as a microwave or printer, these pieces of equipment will not function successfully using a modified sine wave, lights will buzz slightly and electric fans will hum, this does not occur with a true sine wave inverter.

help choosing your converter

image of pure and modified sine waves

True sine wave inverters will also cause less damage in the long term to attached recharging devices. True sine wave converters are more expensive ranging in price from £150 – £1000 depending on the output watts, but in terms of investment, money saving in the long run.

Initially even before looking for an inverter you will need to determine the maximum amount of 120 volt AC power you and your crew are going to require at any one time.

Please remember though that the inverter runs from your battery, so you will need to keep a close eye on the state of your battery bank. This obviously won’t be an issue if you have an engine alternator running.

The best way to work out Watts’s usage is to check the data plate on the appliances. Although even this is not infallible as wattage will vary depending on the selected power setting of a motor driven gadget, for example a small electrical fan heater set on high will use additional power.

The equation should be volts X amps = watts, for example my laptop runs at 19V 1.75A which will equate to 33.25 watt’s.

I would recommend that you create a chart, initially going round and listing all the electric items on the left hand side of the page, in the next column, Volts for each item, and then Amps, followed by calculated Watts. This will make it easier in the final column to calculate the accumulative Watt’s requirement.

It is then recommended that you add an additional 20% to the number of watt’s required; this will then give you a correct indicator for the size of the inverter required. You should also consider how you attach equipment to your converter, how many plug sockets or USB points will you require?

I hope that you have found this article helpful, if you have any helpful comments for fellow sailors we would be pleased to hear from you.

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