How to Buy Solar Panels – making sure you size your system correctly

How to buy solar panels for home?

How expensive would it be to buy solar panels to power your home? Are solar panels worth the cost for homes? What is the most cost-effective way to convert my home to solar power?

When you decide to install a renewable energy source and go out to buy solar panels for your home one of the first things you need to do is make sure you get the right size system.

In this post, I’ll describe what you need to include in your calculation to make sure you slash your energy costs without spending more than you need on your systems.

Where to buy solar panel

So here’s a checklist of the things you’ll need to include in your calculation.

Average Power consumption in your home

When you measure energy consumption the most common units are kWh (kiloWatt Hour). For example, 1 kiloWatt hour is the amount of energy consumed in one hour by an appliance rated at 1 kW (kiloWatt). The calculation for this in:

   Energy = Power x Time.


You could try working out the energy consumption from the power rating on each appliance (usually on a label near its power connector) and adding them all up.

However, you use different appliances at different times of the day so this can be tricky. A better way is to buy an energy consumption device and monitor your energy usage across a couple of weeks.

This should also show you the peaks and troughs. If you combine this with a review of your last two or three energy bills you should get a pretty good idea of your power needs.

Let’s use a figure of 6kWh over an average day for the sake of example.

Solar Energy availability

The size of the system you need will also be based on the amount of sunlight your house receives each day. The technical term for this is “Insolation”.

You don’t need direct sunlight to power a solar panel as they work even on cloudy days.

However, depending where you are in the world, the amount of sunlight you get will vary.

Homes nearer the equator get more sunlight than those nearer the Poles, of course!

Although you may have ten hours of daylight where you live some of the days the sun is low in the sky and this delivers less energy from your solar panels than at midday.

If you look up Insolation Tables you might find, for our example, the average day’s total sunshine in your location is 3 hours per day.

We know we need 6kWh in each day therefore 6kWh divided by 3 hours gives us  power requirement of 2kW from our home solar power system.

charge 12v battery with solar

So far you will have calculated your AVERAGE energy consumption. But DON’T specifies your system against this number.

You now need to allow for peaks in demand to make sure you never run short of energy. Take the figure you came to in the last calculation and add 30%.

That is, 2kW plus 30% = 2.6kW. This is the rating you need to use for specifying the solar energy system for our example.

If you take these things into account you’ll be able to get a good idea of the size of the installation you need to replace your household energy with solar power.

 Why Buy Solar Panels – is it worth it? Solar Energy Systems payback.

The short answer is “Yes”. In fact there are lots of reasons for using solar power in your home. We all know about the benefits to our planet when we use renewable energy sources.

But what about the financial question – “What is the payback period?”.

Well, as you might expect, the answer is “That depends!” Obviously it depends on the type of installation you have, how much energy you use, what your current energy costs are from your supplier, and so on.

So everyone’s situation is different.The best way to do any calculation is to look at all the component elements that make a measurable contribution to payback.

Here are some of the biggest contributors so you can work out your own personal payback.

Energy Source

When you compare solar energy with any of the traditional sources (oil, gas, coal, nuclear)  there’s one major difference. Your energy source is unlimited and free.

All the others are consumable. In the last five years, energy costs have pretty much doubled. In the next ten years it is expected to treble (again). So if you were paying $1000 a year in 2004, that would be over $2000 today and $6000 by 2020 (based on recent studies by Ernst and Young).

Add that up over a twenty year period and that total energy cost is enormous. You will get twenty years of service from a home solar energy system and all the energy comes FREE from the sun! But, theres more…

Maintenance Costs

Energy systems in the home that are powered by oil, gas or coal need regular maintenance and have moving parts that wear out in time.

You can expect to replace some of those parts during the lifetime of the system and pay for regular servicing to make sure your system is safe and efficient.

There is almost no maintenance for solar energy systems. So add up your maintenance costs, that go with your energy bills, and work out what that comes to over the next twenty years.

Grants for renewable energy

Most governments have started to introduce incentives to homeowners who are switching to renewable energy sources. For example, in the UK you can get a contribution of up to £2,500 (c. $3,400) against the cost of a solar panel power system.

Sell power back to the grid

In many countries, if you are creating your own energy you can be connected to the grid so you get paid for any of the energy you don’t need for yourself.

Search on “Feed-in Tariffs” for your country. This way you literally get money back from your home solar energy system!

The future value of your home

It is becoming easier to sell houses that take most or all of their energy from renewable sources. In many countries when houses are bought or sold they will be subjected to some kind of survey.

Over the next ten years houses with solar or wind powered energy sources will be more attractive to buyers than houses with traditional systems.

This all sounds great, and there’s a lot of hype about solar energy.

The downside is that the equipment costs and the installation costs are quite high (although they are coming down as the technology develops and matures).

A realistic expectation, taking all the above into account is that your home solar energy system, on average, will take six to twelve years to pay back.

That might sound like a long time but there’s one last thing to remember.

Once you’ve paid off the cost of the system your energy becomes FREE. In fact, if you produce more than you use and sell it back to the grid you can even profit from it. In summary, well worth doing!


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