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Justifying The Cost Of Solar Panels


Durbanite
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For sometime we have been debating whether to have a solar panel fitted or not and got around to doing some maths. To have a 120w solar panel with a MPPT charger fitted costs in the region of about £400. Before any one says anything, we need the epanel to be fitted and the cost is £60. If we are off EHU for 30 days in total we save about £4 per night or £120 overall.

Our fridge on its own uses 420gm gas per 24hours, the cost will be about £21 gas used in the 30days. Minus this from the £120 saved and you are left with £99 saving. If you add in the cost of heating the hot water and cooking, this probbaly knocks off at least another £14 bring the saving down to about £85.

Divide the £400 by 85 and it takes you over 4 1/2 years just to break even. If my figures are correct surely this means that fitting a solar panel is not really a viable option unless you rally a lot or spend weeks on a site with no EHU.

Granted we could opt for a lower wattage panel, but there is not a significant difference between the 100w and 120w panels. A 80w panel which we think is the absolute minimum is about £100 less.

The only real advantage I can see at the moment is that the battery is topped up during the winter and you can use CLs that are sometimes better located to an area than others with EHU and they are quieter CLs.

Can you persuade me otherwise?

 

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If you're in the slightest bit a DIY person, get all of the parts you need from ebay and fit it yourself. I did a 150w panel on my Senator, took about 2 hrs and cost just a fraction under £200 including all of the mounting brackets, controller, adhesive etc.

 

Since fitting it I have been away several times without ehu and it's been fine. I have seen peak charging currents of 9 amps which is about right considering the panel is flat. Your additional budget could be used to double up on panels which would make best use of your controller and provide a lot more power.

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There is more to it than just cost to be factored in . . the solar panel enables you to have longer periods off hook without worrying about "will the battery last out?"

Roughing it . . but in comfort . .

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There is more to it than just cost to be factored in . . the solar panel enables you to have longer periods off hook without worrying about "will the battery last out?"

I would think that the longest we would be off EHU would be about 2- 3 days so maybe a backup battery is a cheaper and betetr option?

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I'm not sure that it comes down to justifying the cost there are more things to take into account and effectively it is a judgemental decision that only you can make.

You could apply the same question to caravans over other forms of excursion. Tents are less costly, accepted in more places at lower charges etc, but we have chosen to caravan.

Pete
Range Rover(s) towing Buccaneer Caravel

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Well I got a 50w panel and controller, but the panel isn't fixed to the roof. I bought it to see how the wife felt about rallying. I've got a 85amp/h battery and after adding a guage, to see how it's charing we can in bright sunlight get 3. 2 amps, normally it's about 2. 5. This means that we don't have to worry about running out of juice. We use calor at the moment, but am looking to change to flogas as it seems cheaper, and cant justify the cost of safefill just yet.

 

My setup cost me £80 all in, including cables, panel is freestanding, allowing to move it to face the sun to get most benefit. We use to use haven sites and club sites, but after rallying wife doesn't want to go back to haven, and cost of club sites seems to be getting dearer and dearer. We've broken even after about 18 days away. So depending it can work out a lot cheaper. We keep our van on the drive, and now no longer need to keep it hooked up to keep battery charged, so are saving money there as well.

 

I am going to get a bigger panel, probably a semi flexible one to bond to the roof, and also keep the freestanding one. Our 50w can easily keep up with have 2x led striplights on all nights for the kids, as well as a car radio during the day for something to listen to, we very rarely use the tv though. For gas, we find we use a 6kg bottle for 4 nights in the colder months, and in summer it can last 15 days, so gas costs are minimal. We only switch the water heater on an hour before we need it.

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After 5 years I have upgraded from a 14 to a 43, £50 second hand. ....we have been off EHU for 10 days so far and expect another 7 nights before we return. ....with 2 hours Tv and normal use of lighting we think we will survive!

 

Geoff

Kia Sorento KX-1 CRDI 4WD towing an Elddis Affinity 530

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After 5 years I have upgraded from a 14 to a 43, £50 second hand. ....we have been off EHU for 10 days so far and expect another 7 nights before we return. ....with 2 hours Tv and normal use of lighting we think we will survive!

 

Geoff

Our issue is that the wife likes to watch Sky TV in the evenings so about 5 hours plus use every day. I think that between the digibox and the TV they consume about 90w.

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Around 40Ah per night then, just for the TV.

I work it out at about 40ah for both? 5hrs x 45w/12v=18. 75ah for one unit so 2 would be 37. 5ah? A 120w panel on a good day will input up to 84ah which would then cover the other stuff running like water pump, fridge and lights.

It seems the smallest panel that should be okay would be 80w with output 56ah per day. If using a MPPT charge controller even on a cloudy day the out put should be okay.

I am no mathematical genius so may be totally wrong with my figures.

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I would of thought you could have to factor in the weight of extra batteries and the extra fuel used to carry them around ? some people have upto 4x 120A batteries + the solar panels weight .

 

 

Dave

Jeep Commander 3. 0 V6 CRD

Isuzu D- Max Utah Auto

Elddis Crusader Storm 2000 Kgs, Unipart Royal Atlas Mover .

 

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I work it out at about 40ah for both?.

Sorry, that's what I meant: 40Ah just to watch TV :)

. .. some people have upto 4x 120A batteries + the solar panels weight .

 

 

Dave

What a lot of folk overlook is that they now need to input more charge. More batteries just means more capacity, you still have to put back what you take out (plus say 20% on top).

 

Tony

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I would of thought you could have to factor in the weight of extra batteries and the extra fuel used to carry them around ? some people have upto 4x 120A batteries + the solar panels weight .

 

 

Dave

We wouldn't even consider two batteries as neither one of us would be able to lift them.

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But you can only take out a small percentage of a battery before you start to damage its life this why you need high supply of AH s so you only take a small amount from the battery bank . Thats why you need a extra battery if you have a higher demand and some companies recommend you should have 5x your 24h demand. As said solar can pay if it is used regularly or full timing but if your only going away a few weeks a year stick to EHU or a couple of nights off the grid as it will never give a return

 

A 100 Ah battery needs 120 Ah put back into it or as you say 20% extra

 

 

 

Dave

Jeep Commander 3. 0 V6 CRD

Isuzu D- Max Utah Auto

Elddis Crusader Storm 2000 Kgs, Unipart Royal Atlas Mover .

 

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We have ended up in the last 3 years hardly ever being off EHU or without the generator. Perhaps the odd night here or there on an Aire. Battery gets charged by EHU, car and solar panel. Even in winter I tend to leave the heating on very low to keep the inside dry and stop mould erupting everywhere. About the only thing it does in reality is make sure that the battery stays charged all the time and recharges it if I do something in the van to use power.

Enjoy every minute of every day. It doesn't last nearly as long as you'd like, and there's no guarantee of coming this way again.

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But you can only take out a small percentage of a battery before you start to damage its life this why you need high supply of AH s so you only take a small amount from the battery bank . Thats why you need a extra battery if you have a higher demand and some companies recommend you should have 5x your 24h demand. As said solar can pay if it is used regularly or full timing but if your only going away a few weeks a year stick to EHU or a couple of nights off the grid as it will never give a return

 

A 100 Ah battery needs 120 Ah put back into it or as you say 20% extra

 

 

 

Dave

Thanks probably better to forget about solar altogether and stick to EHU sites. Use the money instead to visit the Outer Hebrides etc.

Edited by DeltaTIowner
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Thanks probably better to forget about solar altogether and stick to EHU sites. Use the money instead to visit the Outer Hebrides etc.

What a strange reaction to the sound and encouraging advice. Each to their own. ....

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What a strange reaction to the sound and encouraging advice. Each to their own. ....

I chickened out initially and decided against a solar panel, but then got brave and put in the order for a 120w panel so we are now going solar. :D

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I disagree with the statement that 'taking more than a small percentage from a battery damages its life'. All use of a battery 'damages its life' as it leads to sulphation and eventual demise. However, the construction of the battery varies (should vary) according to its use, and a proper leisure battery will tolerate comparatively deep discharge well as that is what it is designed for and still last at least 5 years if otherwise well cared for.

Enjoy every minute of every day. It doesn't last nearly as long as you'd like, and there's no guarantee of coming this way again.

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I disagree with the statement that 'taking more than a small percentage from a battery damages its life'. All use of a battery 'damages its life' as it leads to sulphation and eventual demise.

I considered picking up on that point but decided that the subject would start to take a complex path if I did.

 

Suffice to say that DoD and battery life is not a straight curve (if you can have such a thing). The greater the DoD the shorter the battery life. At some figure well below 50% (the figure depends on the battery) the life drops off a cliff.

 

Tony

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Our issue is that the wife likes to watch Sky TV in the evenings so about 5 hours plus use every day. I think that between the digibox and the TV they consume about 90w.

Ouch. ....we don't even do that at home. .....don't have Sky anyway. ....so best of lu k!

 

Geoff

Kia Sorento KX-1 CRDI 4WD towing an Elddis Affinity 530

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Depth of discharge.

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Hi,

If you have motor movers you will have a fully charged battery ready to go !

Skoda Scout 4x4 pulling a coachman Amara 520/4 at 93%---- when full!

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