Tonik house with solar panels

How we calculate your bespoke solar benefits

Feb 19, 2018

With the price of solar power having fallen considerably, what was once seen as a far-fetched fantasy of the future - your own personal solar panels - has become an increasingly realistic prospect for more and more homes, and a good long-term decision for homes looking to produce their own green energy and reduce dependency on grid pricing.

Why we do personal calculations

Nevertheless, solar panels remain a significant investment, and we feel it’s important to help you understand exactly how they could benefit you personally. That’s why we carry out a bespoke calculation for each of our members considering installing solar panels: to make sure you get a clear and honest understanding of what you’d be buying and how you could make the most of it, before you make any kind of commitment.

So in the interests of being as transparent about our methods as possible, here is the precise process by which we calculate your solar benefits - using a method certified by the industry best practice Microgeneration Certification Scheme to forecast how you would benefit from solar over the course of the expected 25 year lifespan of your panels.

Calculating your solar benefits

The MCS method (with whom our partner The Phoenix Works are registered as an official installer) provides a typical generation figure which is accurate within +/-10%, and this figure is measured in energy (kWh).

We then use this figure to establish your approximate savings, by applying the following formula:

Solar benefits calculation

So, for example, if you generate 2000 kWh of energy with your solar panels and use 50% of it in your home, with the price of electricity at 15 p/kWh you would see a reduction of your energy bill by £150 in your first year, as well as receiving £128 of income from the Feed-In Tariff (a government run scheme that pays you for the energy you generate and any excess you export to the grid). That gives you a total first year saving of £278 - but the real win will be that you have protected yourself today against grid price rises that show no signs of slowing, giving you savings in excess of £10,000 over the 25 year lifetime of your panels.  

To forecast your savings over 25 years, we use the official product specification for panel performance, and assume 3% inflation and a 5% increase* in electricity prices per year.

Not only that, but we can calculate how much carbon you’ll be offsetting by installing solar panels.

Solar variables

There are a few other factors which have a bearing on the savings you can make with solar panels, most of which are to do with the location and orientation of your roof. Here’s a quick run-down, in decreasing order of potential impact:

  • How shaded your roof is. As you’d expect, the more shaded your roof is, the less energy you'll generate – but even with some shading, you can still get great solar outputs. As most roofs have some shading, we account for this in our calculations – but we’ll refine this when we visit your home for a design and structural assessment.

  • How much of the solar-generated electricity you use in your home. Obviously, the more of your home-generated solar electricity you use in your own home, the greater your savings will be. This can affect your savings to the tune of +/-15%, but having a battery in your home would help improve this calculation by enabling you to use more energy in your home.

  • Where you live. Different parts of the country receive different levels of sunlight, so your location can make a difference of +/-15%.

  • Which direction your roof faces. There’s a common misconception that unless you have a south-facing roof your home isn’t for solar - this just isn’t the case. The way the sun tracks your home during the day, however, impacts the time and amount of output from your panels -  typically affecting your savings by +/-10%.

  • The angle of your roof. The angle of your roof dictates how directly sunlight strikes its surface, which can impact your savings by +/-5%.

The wider benefits

As well as the benefits determined by the MCS calculation above, it’s worth bearing in mind that solar panels have a broader positive impact as well.

While powering your home with renewable energy from the grid is a great step forward - giving you peace of mind that you’re actively supported clean generation in the UK - you can have an even greater effect by taking matters into your own hands.

There are now over 1m UK homes that have taken the next step; homes that have realised generating your own solar energy not only offers greater independence from the grid and paves the way for big savings, but also contributes towards a greener energy future by increasing the UK’s renewables stock and expanding the amount of renewable generation capacity.

Find out more about our solar products here.

*Reference for electricity price increase figures.



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