Is an 80W panel sufficient for a motorhome?

Have just bought a motorhome and want solar panels suitable for long term living in van.  Would your 80w panel be sufficient, and what other items would I need ready for fitting this panel on my van?
Thanks - Andrea

Hi Andrea,

Whether 80W is sufficient depends entirely on what appliances you want to power! In the summer, for a few lights / water pump / radio etc it would be more than adequate; in the winter it might not be enough, especially if you also want to run things like a TV, laptop, or fridge.

Try our solar calculator to get an idea of what appliances you might be able to power.

If you buy the 85W solar panel kit it includes the regulator and all the wiring you need for fitting the panel. The only other thing you will need is some means of mounting it on the roof - it shouldn't be too hard to make up some suitable mounting brackets.

Solar for heat gun and lighting

Hi - I am going to start a business car window tinting in a standard basic garage; however I have no means of electric so I wonder if you have a solution. I need enough energy to power a normal light supply and also to be able to power a heat gun for 2-3 hours (not constant) a day. I do not have lots of money so would be looking for the cheapest solution. Thank you - Kieran

Hi Kieran,

It's possible - but it might not be all that cheap!

You can use our Solar panel calculator to work out how big a system you need. For example, a 40W light for 4 hours and a 1000W heat gun for 30mins per day would need about 516 watt-hours of electricity each day. 200 watts of solar panels would give you that much for most of the year, but probably still not enough in winter.

Some idea of the costs:

200W solar panels - about £800
regulator - £95
batteries - about £150
inverter - £148.

So it does add up!

regards, Andy

Running 240V appliances by solar power

I would like to build a device where a solar panel is connected to a UK standard plug socket, to power UK standard (240 volts I think) electrical appliances.  As far as I am aware I need a solar panel, a diode, a regulator, a battery, an inverter, and a plug socket.  The unit would be stand-alone, not connected to the national grid, but able to power standard 240v electrical appliances, e.g. electric kettles.

My questions are these.  Is this project possible (I assume it is, beacause it can be done on a larger scale by linking solar panels into the house mains electricity)?  How do I calculate the energy input output requirments of the components (can I use any components of different energy flow allowances with each other)?  Do the components have to be conected in a special way?

Thank you, Chris

Hi Chris,

Yes, the project you describe is certainly feasible, and in fact it's quite common to use solar power in this way to power 240V appliances where you don't have a national grid connection.

You can use our solar panel calculator to work out how much power your appliances will take, and how big a solar panel array would be needed to power them. The inverter size you need depends on the maximum power you need to draw from the system - so a laptop charger would be fine with a inverter of a couple of hundred watts; a kettle however would need a 2kW inverter at least.

You don't need a diode in the system if you have a regulator - the regulator stops the panel discharging at night.

regards,
Andy
Midsummer Energy

Solar powered cool box

Hello - I am looking for a solar panel which I can use with a cool box in our motor home. At present the box connects into the cigarette lighter. Is there a panel that has the facilty for plugging in such an item? Thank you - Tony

Hi Tony,

You could fit a cigarette lighter socket to any solar panel very easily, which would allow you to power your cool box directly. Something like the Spectra 20W panel might just be big enough to power a small cool box.

However, you should note that the voltage on a solar panel varies strongly depending on what appliances are attached to it and how much sun there is. Some appliances can accept a wide range of input voltages and would be fine with the variable voltage; others might not like a voltage of perhaps 18-20V applied to them! When you are running off a battery the voltage is very stable, normally between 12 and 14 volts.

Most cool boxes run on peltier cooling modules, which I am fairly certain would work fine when attached directly to a solar panel. However, I can't promise that it would work.

regards,
Andy
Midsummer Energy

Battery types and powering appliances directly

Hi, Could you please tell me in your opinion what is the best battery to use with solar power. Life span and cost are of paramount importance. Also, can you use solar power on very sunny days without charging batteries? Direct to a cooker? I am just learning/starting out to put solar on a caravan/motorhome. Thanks - George.

Hi George,

Standard leisure batteries available from any motoring store are absolutely fine for most purposes on caravans and motorhomes. As long as they are kept well charged they will have a lifespan of at least 5 years - it is batteries that are poorly charged that soon loose their capacity and need replacing.

'Sealed lead acid' or 'AGM' batteries will tolerate being discharged deeper than standard leisure batteries (and also never require topping up with water). But the extra expense is not worth it in most applications.

Cookers consume very large amounts of power - normally several thousand watts. You would need an enormous array of solar panels to power a cooker. It wouldn't really be very practical! In general you are much better storing the power from the panels in batteries rather than trying to use it directly.

Power from horizontal solar panels

Hi. We wish to use solar panels on the roof of a narrow boat, but we do not want to be turning and tilting these panels. So they will be horizontal.  Is it better to use the polycrystalline or amorphous panels in this situation? Regards, Jim.

Hi Jim,

It doesn't make a great deal of difference to be honest - with almost any panel you will reduce the output by about 1/3 in UK latitudes by keeping it horizontal. But personally it's exactly what I do on my own narrowboat - I reckon the saving in hassle in not having to reposition the panels every time I move is worth the small reduction in power!

 

The Unisolar panels (both the framed and adhesive-backed versions) do perform a little better in indirect light than crystalline panels such as the BP Solar and Kyocera panels, so might give you a tiny bit more power in a horizontal position. I would particularly recommend the adhesive-backed panels as a great solution for narrowboats. They are more expensive, but they are extremely easy to fit, virtually indestructible, and look fantastic.

 

hope that helps

Solar for off-grid house in Spain

I would like the price for a full solar energy system to be installed in Spain to run 2 small 3 bedroom houses which have just been built side by side.

The system needs to be off grid, and able to run all potential electric mod cons (though not air conditioning). Thanks, Mike.

Hi Mike,

A typical household in the UK uses around 12.5kWh per day. On a
typical UK summer's day you would need an array of around 2500W of
solar panels to generate sufficient electricity over the course of a
day to replace that power.

On the one hand you have better sun resources in Spain, and with
energy efficient appliances you can reduce the 12.5kWh needed per day
considerably; but on the other hand there will be times - overcast
days in winter - that the panels produce less than 12.5kWh per day. On
balance, a 2500W array will give you a pretty good amount of power to
play with - but you do have to remember that fundamentally a battery
bank is a limited resource, and if people leave all their appliances
on over a couple of dull winter days it will run out!

Your battery bank needs to be capable of storing considerably more
than one day's power, as it's bad for the batteries to be heavily
depleted, and also you have to have a good reserve for those overcast
days when the panels are not doing very much. As a minimum, I would
say a battery bank of 40kWh for a 2500W array.

So, the system components for each house would comprise:
- 2500W of solar panels. Approx cost £9000.
- 32 x 110Ah 12V batteries (capacity= 32 x 110 x 12 = 42240Wh).
Approx cost £2500
- Solar Regulator. Approx cost £200.
- Inverter to produce 240V AC from DC battery bank. Approx cost £1500.
- Wiring, mounting system etc. Estimated cost £1500.

So total system cost is around £14700 per household, plus installation costs.

You may be able to save 10% on that as the figures I have quoted
include VAT of 17.5% - there is a lower rate of 5% on energy efficient
installations on houses in the UK, which you may qualify for.

The cost is pretty much proportional to the size of the system. It is
perfectly possible to run a household on a system half that size (and
half that cost), with careful use of electricity. Many people in
caravans and narrowboats live quite happily with solar arrays less
than a quarter that size or even smaller. On the other hand, if you
want to be able to run everything under the sun (so to speak), you'll
find that even a 2500W array per household is not enough, particularly
in the winter.

Hope that helps - Andy