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How much is too much Solar Power and how much is just enough?


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11 minutes ago, Tony1 said:

 

The name on the front is 'ICEKING', but there's no leaflet for it so no idea about specs- I would guess it was new with the boat 6 years ago.

As far as I'm aware, 40-50Ah per day is about normal for an under-counter fridge without a freezer compartment? So at the moment I'm not looking for a replacement. 

 

Most of the ICEKING fridges are F energy rating, which is about as bad as it gets... 😞

 

https://www.ice-king.co.uk/products/fridges/under-counter-fridges/

 

Power consumption (174kWh/year) is at least 50% higher than better-insulated modern fridges, or getting on for double the best ones (99kWh/year)...

 

https://www.sust-it.net/energy-saving/undercounter-fridges

Edited by IanD
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2 minutes ago, IanD said:

Most of the ICEKING fridges are F energy rating, which is about as bad as it gets... 😞

 

https://www.ice-king.co.uk/products/fridges/under-counter-fridges/

 

Power consumption is at least 50% higher than better-insulated modern fridges, could be double the best ones...

 

Wow, that's a shocker. I'm wondering if they chose this because the space is unusual, and there were not many that fit in there. 

 

The thing is that for 8 or 9 months it doesnt matter anyway, I have enough solar to power it easily. 

 

If I need engine charge on say 100 days each year, and if that does cost me say £50 or so, then a better model would cost about what- £35 for the same amount of usage? 

 

At the moment, as inefficient as it is, the financial case for buying a new one does not seem to be totally clear, if it only saves me £15 per year.... 

 

 

 

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Just now, Tony1 said:

 

Wow, that's a shocker. I'm wondering if they chose this because the space is unusual, and there were not many that fit in there. 

 

The thing is that for 8 or 9 months it doesnt matter anyway, I have enough solar to power it easily. 

 

If I need engine charge on say 100 days each year, and if that does cost me say £50 or so, then a better model would cost about what- £35 for the same amount of usage? 

 

At the moment, as inefficient as it is, the financial case for buying a new one does not seem to be totally clear, if it only saves me £15 per year....

 

Like many other things with boats, changing something that works doesn't always make financial sense... 😉

 

It all depends how much you want to get engine running hours down, and whether your power cost per kWh allows for engine wear/servicing/eventual rebuilding as well as fuel -- my guess is that it doesn't, looking at your numbers.

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16 minutes ago, Tony1 said:

 

The name on the front is 'ICEKING', but there's no leaflet for it so no idea about specs- I would guess it was new with the boat 6 years ago.

As far as I'm aware, 40-50Ah per day is about normal for an under-counter fridge without a freezer compartment? So at the moment I'm not looking for a replacement. 

 

 

Mine is around 28Ah - 30Ah per day. (and it has a freezer compartment) but it does depend on ambient temperatures and how many times you open the door.

Model Waeco CR80

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11 minutes ago, IanD said:

Like many other things with boats, changing something that works doesn't always make financial sense... 😉

 

It all depends how much you want to get engine running hours down, and whether your power cost per kWh allows for engine wear/servicing/eventual rebuilding as well as fuel -- my guess is that it doesn't, looking at your numbers.

 

Thats a good point- engine servicing and running hours can be a very significant cost.

 

My approach is to consider the 100 days or so that I need engine charging each year as the starting parameter/scope. If my rough estimate is right that it uses 40-45Ah per day, or about half an hour of engine running/charging time, then that would be very roughly 50 engine hours per year, just for the fridge. 

 

If I go for worst case of a service costing £150 every 200 hours, then the fridge is currently costing me about a quarter of a service each year, which would be a bit less than say £40 (I'd rather overestimate or round upwards on costs).  

Straight away that doubles my original estimate of the annual costs from £40 to £80.

 

The next question is - how much would a more efficient fridge cost, and how much less power would it use? 

If a better fridge uses half the power, then to be honest its worth a closer look, as that might be about £40 per year.

 

I do have friends and family in this area who would probably be prepared to have a fridge delivered, and drive it to my boat, but in 6 months time I'll have moved southwards and it might no longer be an option.

Its certainly something to think about, but not top of my to do list. 

 

 

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25 minutes ago, Alan de Enfield said:

 

Mine is around 28Ah - 30Ah per day. (and it has a freezer compartment) but it does depend on ambient temperatures and how many times you open the door.

Model Waeco CR80

 

Those are excellent fridges I hear, but I'm hoping my next fridge will be a normal domestic fridge for a couple of hundred quid, but with a very high rating for efficiency

 

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1 minute ago, Tony1 said:

 

Those are excellent fridges I hear, but I'm hoping my next fridge will be a normal domestic fridge for a couple of hundred quid, but with a very high rating for efficiency

 

The problem is that the ones with the lowest energy consumption are also more expensive, because more efficient pumps/cooling and better insulation cost more, and the cheap brands don't bother because they're bought on price not energy consumption...

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1 minute ago, Tony1 said:

 

Those are excellent fridges I hear, but I'm hoping my next fridge will be a normal domestic fridge for a couple of hundred quid, but with a very high rating for efficiency

 

 

 

I like to have various options to allow for some redundancy.

 

It is not unknown for Inverters to decide to "have a holiday" so I double up on everything possible.

My freezer is 230v AC, but the fridge is 12v DC

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2 hours ago, Tony1 said:

My rough calculation is based on the assumption that my engine burns about 1 litre of diesel per hour, during which time it generates about 90-100Ah of charge. 

Only if your alternator is pushing out 90-100 Amps for that hour! And I doubt if it is for longer than a few minutes (unless you are running some high powered appliance at the time, in which case the energy generated is not being stored in the batteries anyway).

2 hours ago, IanD said:

Most of the ICEKING fridges are F energy rating, which is about as bad as it gets... 😞

 

Or in other words they are F KING useless!😃

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17 minutes ago, David Mack said:

Only if your alternator is pushing out 90-100 Amps for that hour! And I doubt if it is for longer than a few minutes (unless you are running some high powered appliance at the time, in which case the energy generated is not being stored in the batteries anyway).

 

I'm not 100% convinced about the 1 litre per hour estimate, but the charging rate of 90 amps plus is actually the one variable I have some kind of accurate idea about.

I use no less than three BMV712s as part of the charge/battery monitoring setup, and I check the charging rate at the start and end of the process. 

Because I have lithiums, the charge rate varies very little if at all- they soak up every bit of charge you put into them.

 

This is why I was very careful not to push the alternators too hard, and check their temperatures during testing - I knew the chosen output that I used would have to be maintained for at least an hour, without them getting too hot. 

I've set the B2Bs up so that they generally stay in bulk charging mode until they are told to switch off, either by the engine being stopped, or by the SoC-monitoring BMV712 unit sensing they batteries have reached the 'normal' upper limit of 85% SoC. 

 

So I can count on a steady 90 amps (depending on ho many of the B2Bs I engage) from start to finish. Lithium batteries are a pain to look after in some ways, but they dont half charge well. 

In the high summer, when the solar panels are throwing another 60-70 amps into the batteries, its more difficult to tell what charger is doing what, but if I'm not sure whether a particular B2B is still operating, I will sometimes use a clamp-ometer to check the current flowing from each of the B2Bs. 

 

Edited by Tony1
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56 minutes ago, David Mack said:

Only if your alternator is pushing out 90-100 Amps for that hour! And I doubt if it is for longer than a few minutes (unless you are running some high powered appliance at the time, in which case the energy generated is not being stored in the batteries anyway).

 

Or in other words they are F KING useless!😃

 

F is the New A

Most chest freezers that are currently rated as A+ will be classed as F under the new system.

 

New energy rating for white goods to help cut your bills | This is Money

 

 

 

Edited by Higgs
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7 minutes ago, Max Headroom said:

Newbie question 

 

Would a twelve volt fridge draw more amp/hour power than a 240v fridge drawing 12v through an inverter (same load). 

Thankyou 

Depends...

 

12V fridges are more expensive and not as efficient as good quality 240V fridges, so the fridge itself uses more power. The inverter has losses (maybe 10%? -- some are worse, some are better) which closes the gap a bit. If the inverter is only there to run the fridge then the inverter itself takes some power, which closes the gap even more.

 

Generally speaking, if you have an inverter anyway then a good quality 240V fridge will be cheaper to buy and run than a 12V one. If you have to buy and run the inverter just to run the fridge, maybe not...

Edited by IanD
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This is an interesting video by Sterling from a few years ago- one of the things that struck me was that there was a decent power saving to be had if there is no freezer compartment. 

My fridge came without a freezer, and I'm ok with the compromises that involves at the moment, but there's no denying that the longer food storage periods offered by a freezer would give more flexibility to stay off grid and away from towns for longer periods, if that is something of interest to you personally. 

 

Now that I have a lot of solar, running a fridge+freezer would not be an issue at all between March and October.

So when the current one fails, I'll definitely give at least some thought to getting a new one with a freezer compartment. 

 

 

 

Edited by Tony1
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16 minutes ago, Max Headroom said:

Newbie question 

 

Would a twelve volt fridge draw more amp/hour power than a 240v fridge drawing 12v through an inverter (same load). 

Thankyou 

 

Ian has summed it up very well, but just as an 'adder' it depends on which model of fridge you are talking about.

My 12v fridge uses less than 30Ah per day but it is an expensive boat fridge, not a 'caravan fridge'.

It depends on the type of fridge - compressor or absorption ?

Some modern fridges have 2 compressors.

And so on.

 

Look at the actual power usage figures for each of your choices (add 10% to the 230v fridge to allow for losses in the inverter) and then you can tell.

 

Alternatively post the fridge models / specifications here and someone will tell you.

 

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5 minutes ago, Tony1 said:

 

This is an interesting video by Sterling from a few years ago- one of the things that struck me was that there was a decent power saving to be had if there is no freezer compartment. 

My fridge came without a freezer, and I'm ok with the compromises that involves at the moment, but there's no denying that the longer food storage periods offered by a freezer would give more flexibility to stay off grid and away from towns for longer periods, if that is something of interest to you personally. 

 

Now that I have a lot of solar, running a fridge+freezer would not be an issue at all between March and October.

So when the current one fails, I'll definitely give at least some thought to getting a new one with a freezer compartment. 

 

 

 

 

That is a useful video, but note that they're comparing a 12V fridge with 230V ones from Lec, which are nowhere near the best for energy consumption -- there were better 230V fridges then and there are *much* better ones now, but the better ones do tend to cost more money -- see here, the best Lec is half the price of the best fridge (Leibherr) but uses almost twice as much energy...

 

https://www.sust-it.net/energy-saving/undercounter-fridges

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36 minutes ago, IanD said:

 

That is a useful video, but note that they're comparing a 12V fridge with 230V ones from Lec, which are nowhere near the best for energy consumption -- there were better 230V fridges then and there are *much* better ones now, but the better ones do tend to cost more money -- see here, the best Lec is half the price of the best fridge (Leibherr) but uses almost twice as much energy...

 

https://www.sust-it.net/energy-saving/undercounter-fridges

 

I was impressed with the performance of the 240v model in the video, so its good to know there are better-performing models available.

 

One thing I noticed with mine is that running the thermostat a bit higher makes a bigger difference than I would've expected to its energy use. I now have mine set at 3, which seems acceptably cool, and my estimate is that it runs (on average) at about 1 amp or less during an 8 hour 'overnight' period.

During the other 16 hours (lets say the 'day'), being opened more often, fresh (and warm) contents inserted etc, the compressor will kick in more often and it will use more- but with all the other stuff running during the day its hard to pin down its energy usage.

I would guess its average might be 2 amps during that period, so perhaps I'm looking at 8Ah overnight plus 32Ah daytime usage over a 24 hour period- maybe 40Ah in total. And that's a fridge with a poor energy rating, as you discovered. 

 

Interestingly, when I set my thermostat at level 6 (of 7), the energy usage overnight was roughly doubled, and the daytime usage would also have increased, although maybe not quite proportionally. The reduction in temp was at most a couple of degrees, judging roughly by feeling the different items by hand.

 

I'm not sure I'm going to attempt all of the necessary maths when the time comes that I need a new fridge. Clearly the expensive models are cheaper to run but more expensive to buy, so perhaps there is a sweet spot somewhere. 

To be honest what will be the main factor for me personally is the unusual size of the under-counter space. Trying to carve out more room for a slightly larger fridge (for someone whose carpentry skills are very rough) does not seem worth the mess and the effort.

So my main initial criteria will be that the new fridge is no more that 50cm wide and 85cm high.

The winner will be the best 'affordable' fridge of that size, by which I mean it's no more than about 30-50% more expensive than the average/standard models available. 

 

Getting 12v wiring installed will also be an expense, so unless there is an outstanding and affordable 12v model, I'll probably end up with another 240v one. 

 

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14 minutes ago, Tony1 said:

During the other 16 hours (lets say the 'day'), being opened more often, fresh (and warm) contents inserted etc, the compressor will kick in more often and it will use more- but with all the other stuff running during the day its hard to pin down its energy usage.

I would guess its average might be 2 amps during that period, so perhaps I'm looking at 8Ah overnight plus 32Ah daytime usage over a 24 hour period- maybe 40Ah in total. And that's a fridge with a poor energy rating, as you discovered. 

 

Rather than guess, why not get a plug in 'wattometer'. Simply plug it into the 3-pin plug, then plug your fridge into it and it will tell you exactly your Wh over any time period you wish

 

Something like this (other models, prices and suppliers are available)

 

LCD Energy Monitor Plug In Electricity Power Consumption Meter Watt Kwh Analyzer | eBay

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15 minutes ago, Tony1 said:

 

I was impressed with the performance of the 240v model in the video, so its good to know there are better-performing models available.

 

One thing I noticed with mine is that running the thermostat a bit higher makes a bigger difference than I would've expected to its energy use. I now have mine set at 3, which seems acceptably cool, and my estimate is that it runs (on average) at about 1 amp or less during an 8 hour 'overnight' period.

During the other 16 hours (lets say the 'day'), being opened more often, fresh (and warm) contents inserted etc, the compressor will kick in more often and it will use more- but with all the other stuff running during the day its hard to pin down its energy usage.

I would guess its average might be 2 amps during that period, so perhaps I'm looking at 8Ah overnight plus 32Ah daytime usage over a 24 hour period- maybe 40Ah in total. And that's a fridge with a poor energy rating, as you discovered. 

 

Interestingly, when I set my thermostat at level 6 (of 7), the energy usage overnight was roughly doubled, and the daytime usage would also have increased, although maybe not quite proportionally. The reduction in temp was at most a couple of degrees, judging roughly by feeling the different items by hand.

 

I'm not sure I'm going to attempt all of the necessary maths when the time comes that I need a new fridge. Clearly the expensive models are cheaper to run but more expensive to buy, so perhaps there is a sweet spot somewhere. 

To be honest what will be the main factor for me personally is the unusual size of the under-counter space. Trying to carve out more room for a slightly larger fridge (for someone whose carpentry skills are very rough) does not seem worth the mess and the effort.

So my main initial criteria will be that the new fridge is no more that 50cm wide and 85cm high.

The winner will be the best 'affordable' fridge of that size, by which I mean it's no more than about 30-50% more expensive than the average/standard models available. 

 

Getting 12v wiring installed will also be an expense, so unless there is an outstanding and affordable 12v model, I'll probably end up with another 240v one. 

 

The 50cm width (and maybe depth -- how deep is the space?) will be your biggest problem, this vastly reduces your choice of fridge, especially efficient ones...

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7 minutes ago, Alan de Enfield said:

 

Rather than guess, why not get a plug in 'wattometer'. Simply plug it into the 3-pin plug, then plug your fridge into it and it will tell you exactly your Wh over any time period you wish

 

Something like this (other models, prices and suppliers are available)

 

LCD Energy Monitor Plug In Electricity Power Consumption Meter Watt Kwh Analyzer | eBay

 

I'm tempted to get one of these, I must say.

With other things I can get a reasonable idea of their energy usage using the Victron BMV712.

As I'm sure you know, I can also do this with the fridge- but only when its actually running. 

The problem is that the compressor kicks in intermittently as needed, and I cant say how much of the time its actually on. 

 

I think pre-lithiums and pre-solar, I would have had a sharper interest in getting an accurate idea of the fridge energy usage, but as I have all the (solar) electricity I need for 8 months of the year, its become a more academic question. 

Still, it does appeal to my inner academic (yes, very much inner) to know what it uses over 24 hours..... 

 

Edited by Tony1
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1 hour ago, Tony1 said:

 

This is an interesting video by Sterling from a few years ago- one of the things that struck me was that there was a decent power saving to be had if there is no freezer compartment. 

 

 

 

I think he may be a bit bias selling invertors and not fidges. I am sure Shoreline would say the opposite

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2 minutes ago, IanD said:

The 50cm width (and maybe depth -- how deep is the space?) will be your biggest problem, this vastly reduces your choice of fridge, especially efficient ones...

 

The maximum available depth is 60cm, although I believe I would have to leave an air gap. 

I did have a bit of a browse a few months ago out of interest, and I was a bit alarmed at the lack of options.... 

 

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2 minutes ago, Tony1 said:

 

I'm tempted to get one of these, I must say.

With other things I can get a reasonable idea of their energy usage using the Victron BMV712.

As I'm sure you know, I can also do this with the fridge- but only when its actually running. 

The problem is that the compressor kicks in intermittently as needed, and I cant say how much of the time its actually on. 

 

I think pre-lithiums and pre-solar, I would have had a sharper interest in getting an accurate idea of the fridge energy usage, but as I have all the (solar) electricity I need for 8 months of the year, its become a more academic question. 

Still, it does appeal to my inner academic (yes, very much inner) to know what it uses over 24 hours..... 

 

 

It really is a great 'toy' you can see how much boiling the kettle takes, or the toaster, or the microwave, or washing machine cycle and then measure things like the daily usage of the fridge and freezer.

 

I can live without it but its 'stuff', I like to know.

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1 hour ago, Max Headroom said:

Newbie question 

 

Would a twelve volt fridge draw more amp/hour power than a 240v fridge drawing 12v through an inverter (same load). 

Thankyou 

If you really want the lowest power draw possible, do this.  You'll save more electricities than using either a 240v or a 12v fridge.

 

https://www.bimblesolar.com/cheap-solar-fridge

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