Inverter Size Compared to Your Boat Size?

[RupertW]

We have a cheapo 1000w invertor bought a few years ago and only occasionally used until this season (basically for laptop recharging and Torqueedo fast charging if we were in a hurry).

This year I’ve bought some more components and used it to heat hot water from excess solar so it is used every day and I might change it to a more suitable (and alas I guess much more expensive) one.

That is on a 42 foot boat.

 

[CrikeyChris]

I have a Mastervolt 1500W/60A Dakar inverter charger, paired with a 440 Ah battery bank. Will run a 2000W fan heater on the lower heat setting (probably about 1000W) but not for long - a ‘overload’ light comes on the control panel and inverter switches off. Not sure if it’s a fault with the unit but think it is probably due to the battery bank being unable to supply the current at an acceptable voltage. So in short the inverter has to be paired with an appropriate battery bank ( using cables &terminals capable of taking the current).
On a 12m sailboat.

 

[TernVI]

I have a 14ft racing dinghy, self inverting.....

 

[AndrewB]

I have a square-wave 1000w inverter, bought to allow power tools to be used briefly for pressing jobs when away from mains power. Any kind of extended use would soon flatten the batteries. My nominal 70A engine alternator can't keep up.

Does anyone know if its OK to use a square-wave inverter with a microwave oven? I tried mine briefly and it did appear to work though the oven gave out an alarming noise.

A square-wave inverter definitely doesn't work with small induction chargers e.g. Braun electric toothbrush. In fact it kills them. This has been said here before.

 

[FlyingGoose]

I have a square-wave 1000w inverter, bought solely to allow power tools to be used briefly for pressing jobs when away from mains power. Any kind of extended use would soon flatten the batteries. My nominal 70A engine alternator can't keep up.

Does anyone know if its OK to use a square-wave inverter with a microwave oven? I tried mine briefly and it did appear to work though the oven gave out an alarming noise.

A square-wave inverter definitely doesn't work with small induction chargers e.g. Braun electric toothbrush. In fact it kills them. This has been said here before.

pure sine wave for microwave only , you will blow the oven over time

 

[noelex]

We have a 49 foot boat and a pure sine wave inverter with a P30 rating of 2500VA. So we have close to 2500w for resistive loads (such as the electric kettle).

However, the size of the inverter is more related to the devices you wish to run rather than the size of the boat. It is worth keeping the inverter on the small side as much practical while still having enough power to run the maximum loads. Don’t forget start up loads, power factors and ambient temperatures. Some reserve is needed to allow for these factors.

In our case, in the better months we have plenty of power for electric cooking and water heating, so the inverter is sized to run an induction hot plate and electric kettle. It also runs power tools and a washing machine. Other than these higher load AC appliances, the rest of the boat equipment is on 24v so in winter months when electric cooking becomes unviable, the inverter is only infrequently used.

 

[CLB]

This thread is nuts. Inverter size has nothing to do with boat size.

I have a 35 foot boat, what size shoes should i wear ?

I agree. A much better question would have been relating inverter size to battery bank size. Now that might have been interesting.

BTW, is there a general rule of thumb for such things. Ie X watts of inverter per 100Ah of battery bank? I know, in practice, there are many pieces of string of many different lengths, but sometimes there are basic guides to follow if you have nothing else to go on to provide a very rough starting point.

 

[paulajayne]

Victron 5 Kva multi with 900 Amp/h house bank and 5 Kva Genny - 48 foot Ferro Ketch liveaboard.

Living on board and crossing big wet bits it is nice to have home comforts - Microwave, induction hob ETC.

 

[Norman_E]

Again this issue has no relation to boat size, but to the uses you need the inverter for. My boat is 45 feet, but its irrelevant. When I bought the boat it had a CLD Systems inverter of 800 or 900 watts driving a mains voltage fridge compressor. That was a fully automatic inverter that drove the compressor when there was no mains input. When the inverter failed it could not be replaced so I fitted a 1500 watt inverter and a switching arrangement that allowed me to run the fridge directly grom mains, or via the inverter. I chose 1500 watts because I needed to be sure that the inverter would cope with compressor start up current.

 

[prv]

BTW, is there a general rule of thumb for such things. Ie X watts of inverter per 100Ah of battery bank?

I think it would depend too much on what you intended to use the inverter for, in particular how long the loads would be on.

Pete

 

[CLB]

I think it would depend too much on what you intended to use the inverter for, in particular how long the loads would be on.

Pete

Yes, that was one of the pieces of string I referred to. I guess, in theory, you could have a 3kW inverter on a 100Ah battery bank and use it for the full 3kW as long as it was for a very, very short amount of time. I have toyed with the idea of fitting an inverter for years, but keep coming back to the fact that my 230Ah domestic bank is not really ideal for a large inverter, and then when I start to think about a smaller one, I begin to wonder what I would use it for that cant be dealt with by the stand alone 300W plug-in jobbie that I already carry.

 

[cherod]

I'm looking to get some info on your boat size and the size of the inverter you chose... I'm familiar with the fact that you should add up all your devices wattages and choose an inverter from there...

But, out of curiosity, what size and kind of boat do you have, and what size inverter did you choose to install?

May you have fair winds and following sea,

YannikPronto

34’ boat. Don’t have any 240v equipment on board except the battery charger and the hot water element, so don’t have any inverter.

Pete

Is your hot water element 12v / 240 ( only used when plugged into the wall ) / both ,,, What size is the element and tank pls ?

 

[cherod]

,44 ft boat. 3000w pure sine wave inverter to run power tools and watermaker in the unlikely event we lose the genset. Its switchable to all power outlets in the boat. We also have an 800w pure sine wave inverter for small stuff. This one is wired to a dedicated socket on the nav station

Quite comprehensive ?

 

[prv]

Is your hot water element 12v / 240 ( only used when plugged into the wall ) / both ,,, What size is the element and tank pls ?

Like the vast majority of yacht hot water systems, it’s 240v and powered only from shore power. I don’t remember the element rating; maybe 1000 watts? The tank is relatively small but gets much hotter than a domestic system, so that you use less hot water and more cold for a given temperature at the tap. When away from marinas (which is most of the time) it’s heated by the engine. It gets up to temperature pretty quickly and stays hot well into the next day, so we only need to resort to the kettle if we don’t motor for two days.

All very standard and the same as the majority of boats out there.

Pete

 

[cherod]

Like the vast majority of yacht hot water systems, it’s 240v and powered only from shore power. I don’t remember the element rating; maybe 1000 watts? The tank is relatively small but gets much hotter than a domestic system, so that you use less hot water and more cold for a given temperature at the tap. When away from marinas (which is most of the time) it’s heated by the engine. It gets up to temperature pretty quickly and stays hot well into the next day, so we only need to resort to the kettle if we don’t motor for two days.

All very standard and the same as the majority of boats out there.

Pete

Ty , so it is a colorifier ( not wholly dependant on the electric element ) did you fit the system your self or did it come . ?

 

[cherod]

42ft 600w quasi , never use it unless the child needs a laptop on .
everything else is 24v , never missed 240v , although the wife wants a hairdryer, I suggested the bilge blower, she hit me

So you have a 42 ft boat which i assume has a fairly large batty bank , why do yiu not fit an inverter , they are cheap and easy to install ,,, ( just asking ) ?, ty R

 

[FlyingGoose]

So you have a 42 ft boat which i assume has a fairly large batty bank , why do yiu not fit an inverter , they are cheap and easy to install ,,, ( just asking ) ?, ty R

680 amps and a small inverter for the daughters laptop , everything else has been re wired to 24v and 12 v , I put in USB sockets in all cabins and have a large gas storage , I can take 2 x 15 kg bottles , no microwave, have never owned one , even in the house, nothing like a whistling kettle for your tea on the gas hob.
Strange that we think we need 24Ov But we don't really , fora long term cruiser power needs are different, washing machine, water maker , etc. but for the UK na no need
So no need for 240v , the bilge blower was not a good idea, so I Have to turn the heating on and the wife leans down and dries her hair muttering to herself and sending profanities my way,

 

[JumbleDuck]

This year I’ve bought some more components and used it to heat hot water from excess solar so it is used every day and I might change it to a more suitable (and alas I guess much more expensive) one.

Are 12V immersion heaters not available?

 

[RupertW]

Are 12V immersion heaters not available?

Of course but depending on the cable run from batteries to tank they are incredibly efficient at heating expensive thick cables as well as the water. Our run is nearly 5 metres. A 240v element works when we most need it at the marina but can also be used using the same thin AC cabling (even with stepped down voltage to match solar input) when at anchor or sailing.

 

[Buck Turgidson]

Are 12V immersion heaters not available?

google gives lots of options up to 600W. not sure how long that would take to heat a reasonable (25l?) amount of water? I wash in a bucket so a kettle full meets my needs