How To Use Solar Energy In The Home – Why Use Solar At Home?

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How to use solar panels at home

Back in the 70s solar thermal heating was all the rage. That’s to say, it was very cool but in many Western countries people needed a little convincing.

The systems often didn’t look conventional enough for the average home-owner. They were bulky and spoiled the line of the building (as if that mattered when we’re destroying natural resources like gang-busters!)

Solar PV electric systems were around at that time – they’ve been around since 1949, can you believe – but they were expensive.

Even in 2000 solar panels were 3.5 times more expensive than now, so what happened? China happened. That massive nationwide manufacturing facility engaged gears and things change forever.

How are solar panels made?

The 2 main types of solar panels, monocrystalline and polycrystalline, are made from the same material but in a different way.

The core of all solar cells is a thin wafer of silicon crystal doped chemically in a certain so that electrons move freely in one direction and create an electric current when stimulated with sunlight energy.

A solar panel is an energy conversion process which is about 23% efficient at its commercial best. This means that for every 1000 watts of sunshine energy falling on 1 square meter of panel we get about 230 watts of electrical power.

It isn’t a very good deal, is it?

How long do solar panels last?

Many manufacturers give warranties up to 25 or even 30 years, but the panels don’t just stop working. No, they are guaranteed to still supply 80% of their original power when new.

A 100 watt panel will supply 80 watts in 30 years. That’s not too shabby.

Even then, solar panels are not ready for the scrap-heap. They will keep working away at a reduced rate for another 20 to 30 years – a 50-year working life is not a bad deal, much like a human being!

Are solar panels worth it?

I suppose most people would mean are they worth it financially, but our world is moving far beyond this way of reckoning – and very quickly.

We are moving towards a time when all resources, even clothing and food, will become in short supply. There are no complex reasons but just one – we are using everything up on the planet.

Whatever we can conserve is worthwhile because one saving has a knock-on effect on others and hopefully we can see our foolishness before it’s too late.

Anything that helps us utilize or create energy without belching smoke and dirt everywhere is winner in my book. Unfortunately, if only it were as simple as that …

Do solar panels cause pollution?

On the face of it solar panels seem quite inert. They are mostly glass, over 90%, but that glass has impurities such as lead and cadmium floating around in it.

It isn’t such an issue now because there are relatively few solar panels due for retirement but in the next few decades there are going to be millions of tons of old solar panel looking for a permanent home.

Meanwhile, there is little else we can do but make use of them to reduce our reliance on obvious fossil-fuel choices and at least try to keep our local living environment clean and healthy.

Ways to use solar energy.

13 Solar Uses Web Story

This is a bit of trick subject. Of course there’s only one way to use solar energy and that is to convert sunlight into electrical energy, so we can use it.

It isn’t until we really sit down with a pencil and paper and brainstorm it that we realize how many places and in how many ways we could use solar if we put our mind to it.

The obvious one is to go the whole hog – why not power the whole house with solar?

1. How many solar panels to power a house?

How many solar panels do I need for my home?

The average American house uses about 900 kWh/month, which is quite some power. Some houses use twice as much while other not so much, like everything else in life.

Taking this amount of energy, what would it take to convert your house to solar panels?

In passing, I’ll just say that the average U.S. of electricity is 13.5 cents a unit (a unit is 1 kWh), so solar power is well-worth considering. Let’s look at some numbers:

  • Average energy consumption = 900 kWh/month
  • It would take between 20 and 30 x 300Watt solar panels to supply the energy for the average house

There are a lot of variables here but thousands of householders are taking the road to energy freedom by the solar route.

The great thing about solar PV is you don’t have to go the whole hog. You can keep connected to the utility company (called grid-tie solar) and generate just part of your energy needs, or disconnect and go off-grid.

If you do stay on the grid and generate more power than you need, you can have a contract to sell the surplus back to the grid – sounds good, doesn’t it?

Off-grid is very tempting but there are hidden costs, such as buying quite a big battery bank to make sure the household can make it through the night!

It’s one thing having a huge solar panel array pumping out electricity in the middle of the day and quite another in the middle of the night.

In fact, with a fixed solar installation the amount of energy generated early morning and late evening is pretty derisory as well.

Most installers size a system by multiplying the power rating by 4 hours to give a reasonable assessment of the amount of energy you can realistically expect.

This can be increased by installing the solar array on an automatic sun-tracking mechanism, which can improve things by up to 65% but of course the downside is the capital cost. Cost analysis of each individual situation is needed.

Many States have a variety of tax credits, preferential loans and outright grants directly related to domestic and small business solar.

  • There are almost 1.5 million solar panels in use in the U.S.
  • The average domestic solar installation is 5kW (about 20 panels x 300 watts)
  • USA has more solar power workers than all the other energy industry combined
  • Almost 40% of installed solar in the US is in California
  • Solar installer is the fast growing job sector in America

Can you see where this is heading? Maybe it’s time to get on-board. Try the solar calculator below to see how many solar panels you might need for your home:

2. Can I use a solar panel to charge my phone?


iPhones, tablets and other charges seem such small things, that we hardly take them into account when adding up our electricity bills.

However, the global electrical energy bill amounts to billions of dollars! Look at the numbers:

  • Smartphones in the world is approximately 3.8 billion
  • Cost of charging 1 smartphone per year between 25 and 45 cents, say 35 cents/year
  • Total cost charging the world’s smartphones = 3.8 x 0.35 usd = 1.33 billion dollars!

That’s 1330 000 000 USD!

And that doesn’t include other charges for games, ipads, tablets, laptops and desk computers – even your WIFI box costs $10 a year to run. The total cost of charging is really massive.

Paradoxically, this burden on the planet’s resources is the easiest to address. Big projects take big finance and organization, but tiny charging jobs can be taken care of quickly and cheaply.

How to use a solar panel to charge a battery.

Charging smartphones with solar panels only if regulated

There’s all manner of advice and information about charging all kinds of appliances and it pays to check carefully before hooking up expensive electronic devices to solar panels.

All larger solar installations have their output regulated by a solar charge controller. This serves a crucial purpose – to keep the voltage down to a safe level so that the device isn’t damaged by allowing too much current to flow.

A battery needs a certain amount of charge at a certain voltage – if a higher voltage is maintained for too long, damage will result.

If it were me (and it is!) I would purchase a folding solar panel such as one of the high-quality Dokio models and use that as a central charger for all my devices.

It can sit on the inside of a window and also charge up any batteries you might need topping up.

The Dokio panels come with a dedicated solar charger that can charge a lead acid or lithium ion battery, but also features a couple of UBS-style 5 volt outlets that are just perfect for phones and tablets.

The batteries in these devices charge on a ‘constant voltage’ basis and the USB configuration ensures that the voltage is always within limits.

Can I connect a solar panel directly to a phone charger?

In order to connect any solar panel to a smartphone directly it would have to be very low power indeed if the battery isn’t going to overcharge.

A typical ‘large’ solar panel of 50 to 100 watts are known as ’12 volt’ solar panels, which is a nominal voltage. The actual open circuit voltage is much higher, about 21 volts.

Normally, when connecting such a panel to a load, the voltage is pulled right down as it tries to draw current. Some 12 volt DC devices might run but most will not.

However, the current draw from a charging smartphone is very low and the there is a danger of the solar panel voltage being too high. In this case the battery will eventually to pull too much current and get damaged.

The trick is to purchase a very cheap PWM solar charge controller and connect it to the panel. You don’t need to have a battery on charge, just plug in the phone to the USB outlet on the controller and you’re good to go.

PWM solar charge controller can charge a smartphone

All well and good but what about those times when the sun doesn’t shine?

The best all-round solution to ensure charging power 24/7 is to use a solar battery bank. These range between 16000 and 26800mAh and consist of a pack of lithium ion batteries housed in a compact form with a folding solar panel ready connected.

These charging packs can charge your phones and tablets up to 10 times before needing recharge with the sun.

3. Do Solar Attic Fans Work?

It’s generally accepted that attic fans need to be pretty big to have much impact. From what I read around the net most solar attic fans are not powerful enough at less than 1000 cubic ft per minute to make much of a difference to incremental temperature.

At least having a solar fan would solve one of the issues surrounding attic fans – where to set the thermostat.

There’s no doubt in my mind that attic fans or whole house fans can help regulate house temperature, if settings are correct, but that’s a whole other discussion. Suffice to say that our focus is using solar to reduce energy consumption.

It makes little difference to wonder whether the thermostat should be set at 96 degrees or 125 degrees if the energy to drive the fan comes from solar.

The solar output is going to be high when the temperature is high, almost by definition, so it’s well-worth converting to solar.

Remove attic heat with solar attic fans

There is a difference between attic fans and whole-house fans, and they are very often confused.

  • Attic fans – used in day-time and night-time. Exhaust hot air and pulls in cooler air from under the roofing eaves
  • Whole-house fans not used in day-time (especially if AC is used!) because the cool air will be sucked out of the house and replaced by hot. Used at night to replenish the house with cooler night air

The best modern attic fans are not only solar but speed modulated as well, so the amount of heat pulled out is a function of temperature.

This keeps the noise down. It’s also possible to automatically switch backwards and forwards between solar and mains to make sure you have power at night.

4. Solar Flashlights and Lanterns.

It makes complete sense to change all the home’s flashlights over to solar right now – it’s a no-brainer, as they say. Anything with a battery is crying out for conversion. And while you’re about it, make sure all those incandescent bulbs are change out for l.e.d. modules.

L.e.d. lamps use 10 times less current than incandescent lamps for the same light output, so the flashlight is going to give you light for 10 times longer.

How does it do this? Light is produced when electrons pass through the P-N junctions of these electronic devices and it is basically a cold process.

Old-style lamps heat up a coil of wire and it is this which creates light. It’s very wasteful as the light is a by-product of the main physical process, which is to make heat by passing a current through a high resistance wire.

Not only are l.e.d (light emitting diodes) cheaper to operate, they generate more light.

Solar led flashlight and lanterns

If buying new, look for flashlight or lantern models with a solar charging option. These can hang on the wall in the kitchen or garage and connect to an outside solar panel by cable.

If you change over the bulbs in you old flashlights, make sure all the batteries are rechargeable and purchase a universal solar charger that accepts all commercial sizes of rechargeable batteries.

5. Can You Run A Trolling Motor Off A Solar Panel?

Do you have a kayak or canoe used for please or fishing? This is a great example of how we can use solar for leisure.

There’s a whole DIY industry springing up fitting out small inflatable and rigid boats with electric trolling motors either powered by solar-charge batteries or directly from solar panels.

My blog post ‘DIY Solar Kayak’ shows exactly how to do it.

Mounting a solar powered electric trolling motor on a kayak

It is possible to run a low-thrust trolling motor directly from 300 watt solar panels mounted overhead using an electronic device called a ‘buck converter‘ which stabilizes the voltage at 12 volts and maximizes the current output of the solar panel.

For most people, the most viable arrangement is to hook up a light-weight lithium phosphate battery in place of that huge old lead-acid monstrosity and let the solar panel keep it topped up.

A 30 Ah LiFeP04 battery will run for many hours with a 100 watt solar panel and will last a lifetime.

30 lbs Trolling Motor
Set Speed 4 = 20 A

Deep-cycle Pb Battery Size (Ah)

Hours Running Without Solar Panels

Hours Running With 150 Watt Solar Panel

Hours Running With 300 Watts Solar Panels 

40

1.6

2.6

8

60

2.4

4

12

90

3.6

6

18

10

4.4

7.3

22

6. How Much Solar Power Do You Need For An RV?


Although there are RVs with huge amounts of solar on-board, this is generally not done extensively, for a couple of reasons. First of all, even though prices have come right down, it’s still expensive and it isn’t strictly necessary.

The idea is not to ‘run an RV with solar‘, but to extend the autonomy the vehicle already has in the battery bank.

Let’s say an RV has a deep-cycle lead acid battery of 120Ah, which is about typical for a Class C camping car. Even without running AC this battery is only good for 4 or 5 hours. Why?

Because deep-cycle lead acid batteries have a recommended DOD (depth of discharge) of 50%, so 120Ah becomes 60Ah – not a lot of capacity.

It does cramp your style a little to run out of electricity out in the boondocks, even though modern campers have facility to charge both engine and cab batteries from the engine.

Most RV owners with solar have a compromise arrangement whereby they have between 300 and 500 watts of solar panels, and MPPT (Maximum Power Point Tracking) charge regulator and a battery capacity of between 200 to 300Ah (about 2400 to 3600 watts).

With this kind of power, if you go easy on the air-con, it’s possible to go boon-docking for a day or two, particularly if you hook up a small wind-turbine to assist the solar.

Boondocking RV with 300 watts solar panels and 200Ah batteries

Read about MPPT controllers here. RV owners should consider changing out their old lead-acid cells for lithium phosphate – they are safer, last longer and have more capacity for the weight. On the downside they are more expensive to buy, but they can last a lifetime.

7. Can You Run A Water Pump With Solar?

Any pump that is set away from the house or runs automatically according to pressure or liquid level is a prime candidate for solar power.

Perhaps set a sprinkler to wet the lawn when the sun comes out so it doesn’t brown it, or bring water up from a well to run a pond waterfall – the possibilities are endless.

One idea I like has been implemented many times on off-grid homesteads or similar, where there are some acres of hilly land with streams and ponds.

The idea of off-grid solar normally involved purchasing a sizable battery bank. It doesn’t matter which type of battery you buy, lead-acid or lithium, they are all expensive!

Incredibly, it isn’t a very good way to store electricity but it’s one of the best we’ve got – and at least it’s clean. Some homeowners take a leaf of of the large-scale water storage organizations who move around millions of gallons of fresh water.

Many people are thinking outside the box and storing their electrical energy from photovoltaics as … water! It works like this:

  • A solar panel drives a water pump with a DC motor
  • Water is pumped from a pond or stream to a reservoir at a higher level during daytime
  • The water flows back down to the stream at night, reverses the pump motor which generates electricity

It elegant in its simplicity and it’s relatively low tech.

8. Charging A Car Battery With A Solar Panel.

There’s a lot of confusing information out there about this subject. Of course, you can hook up any old solar panel to a 12 volt car battery, and the battery will charge. The big question is ‘will it stop when you want it to?’.

Solar panels come in many different sizes, from 1 watt to 400 watts. That’s quite a variation.

Not only that, but they have different nominal voltages, which in turn depends on how many individual solar cells they contain. A solar panel with 36 solar cells is called a 12 volt nominal cell and it can be used to charge a car battery.

Using a solar regulator to charge a 12 volt car battery safely

However, that’s not the whole story.

The open circuit voltage of a so-called 12 volts solar panel is between 18 and 20 volt. When such a panel is connected to a battery, the voltage is pulled down to the battery voltage and a charging current is drawn.

If the battery is well-discharged, it can pull quite a lot of current with no harm, but as it charges up, it needs less and less.

If the sun is strong and the solar panel has a high enough rating (even 5 to 10 watts may be too much) then the voltage will be too high and too much charge current will flow.

Eventually the battery will be damaged. There are two ways to charge a car battery with a solar panel:

  1. Use a simple PWM solar charge controller set to lead-acid. This can be left attached to the battery
  2. Use a very low power solar panel of 1 or 2 watts. This can also be left connected as the output current is about the same as the float charge current of the battery

9. DIY Solar Generator For Camping.


Camping is a must in summer but I must admit to missing some of the luxuries that modern living provides, such as mains power for small appliances.

These all help to make the outdoor experience that much more pleasurable. Solar generators are available commercially but IMO they are expensive for what they are.

Solar technology is very approachable by the newbie and there’s plenty of advice available on the net for anyone wanting to make their own solar generator (like this blog, for example!)

What Is A Solar Generator?

It’s the same as a electrical generator driven by a petrol engine, except it’s driven by a solar panel and the energy is stored in a battery. All energy on our planet comes from the sun, whether it’s stored in petrol, liquid gas, coal or batteries.

A solar generator converts sunlight directly into electricity and stores it in batteries for future use. They are clean, about the same weight and of course, silent!

Solar Generator Components.

This is what you will need to make your own DIY 2000 watt solar generator:

  • 150 watt flexible solar panel (5 times lighter than rigid)
  • MPPT (Maximum Point Power Tracking) solar charge controller
  • 60Ah lithium phosphate 12 volt battery
  • 2000 watt pure sine wave inverter (converts DC battery voltage to AC mains)
  • 2 or more AC outlets

Add some wiring and you’re good to go! A word of advice – make sure you buy a pure sine wave inverter and not modified sine wave if you want to run electronics while away camping. Modified sine wave types can cause interference.

Even purchasing the best quality components you will save over 50% of the cost of buying a commercial solar generator – and a high-power model can easily be prices around $1700.

10. Solar Lawn Mowers.

Electric lawn mowers beat their noisy petrol cousins whichever way you look at it. If you don’t have one, you should really consider it. If you do have an electric lawn-mower, it’s time to turn it solar.

It’s much easier than you think – there are kits available on Amazon. When the battery runs out simply attach the panel, leave it out in the sun and go for a snooze!

Solar panel charger lawn mower

There are many other automated garden tools available in solar supported format – leaf-blower, motorized electric solar wheel-barrows, garden-karts, electric shears and leaf-cutters, wood-chippers and clippers.

11. Solar Air Conditioning.

Can solar panels really run an AC unit? The truth is that the right number of solar panels can run just about anything but would it be cost-effective?

Appliances like AC units, fridges and freezers are a special case because they have compressors inside driven by motors. This means we have to consider not only a steady current needed to run an AC but also the fact that the motor stopping and starting pulls much more current.

A unit may pull 10 amps normally, but then shut off when the thermostat tells it too, so it draws nothing. When the motor starts up again it might take 30 amps for several seconds, so the system has to be powerful enough to accommodate the extra current.

Normally, a large battery is needed to deliver these load variations, while several solar panels continuously deliver charging current, building up supply capacity ready for the next surge.

Big air conditioning units often have soft-start devices fitted, which apply the voltage gradually so that the current grows more slowly without straining supply capacity or circuit breakers.

Solar air conditioning units

12. Charge Your Electric Vehicle With Solar Panels.

On the face of it, it seems a tall order to charge an electric car with solar panels. Even for a Nissan Leaf 40 kWh battery, it is a huge amount of electrical power.

We need to think in terms of average commute and not absolute range. This means we will most probably have to charge a small proportion of the battery capacity every day, according to how many miles we drive on our daily commute. In the U.S. this is about 30 miles.

If the Nissan Leaf range is 168 miles, then the amount of battery power we would have to replace each day will be:

  • 40kWh x 30/168 miles = 7.14 kWh

Use these figures in the calculator below to see how many solar panels are need to charge a Nissan Leaf:

13. Solar Battery Storage To Guard Against Power Outage.


Recent extreme weather events in America have seen many home-owners without electrical power for several hours, or in some cases, days.

As it is mostly in very hot or very cold weather when power outages happen, it’s even more important to have some kind of backup power to provide services and comfort to your family.

Recent developments in lithium ion battery technology (think Elon Musks’s Tesla EV) have made domestic battery storage a viable proposition.

Tesla power wall solar battery storage guards against power outages

The power-house batteries that drive electric vehicles and provide backup power for homes are made up of small lithium cells having a very high mass to energy ratio i.e. they pack a big punch for a small size and weight.

Most of the time these solar storage batteries sit passively on your garage wall and are kept topped up ready for use by dedicated solar panels.

If there’s an outage, circuit breakers flip and bring the battery online, connecting to the household electrical circuit through a power inverter which converts DC to AC power.

Once grid power is restored, the  battery disconnects and continues to charge in the background.

Related Questions

Can solar panels work with artificial light?

Solar panels work with artificial light to a very low extent. The energy content of light at various frequencies is the important factor. Not all wavelengths convert at the same efficiency.

Can solar panels work withstand hail?

Yes, commercially available solar panels cover hail damage in their general warranty. A common standard is to guarantee a panel from damage due to a 25mm hail-stone hitting the surface at 50mph.

Can solar panels work at night?

Although some researchers are developing solar cells that generate a small percentage of their total power at night, in general commercially available solar panels cannot generate electricity at night or in the dark.

Do solar panels work on a cloudy day?

Solar panels work best when in full sunlight but do work in cloudy conditions when the sun’s rays are diffused. the difference is the amount of power generated, which is a function of the irradiation in watts/m2. This will always be 50 to 70% lower in cloudy conditions.

Will a solar panel work through a window?

A solar panel will work through a glass window but will not generate the same power. Photons scatter as they travel through glass and up to 70% of the energy is lost.

A solar panel will only generate approximately 30% of it’s full power rating when behind glass.


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