I am looking to install rooftop solar on my house some time this year. I have a decent amount of roof space and very little shading so I should achieve fairly ideal conditions for it.

A lot of the companies I've researched appear to offer full "systems" ranging anywhere from 4 to 30 panel installations (with various associated prices) but what I'm unsure about is how extensible a typical solar array is.

Let's say I choose to install 5 panels today. Could I 'extend' my system relatively cheaply with another 5 panels next year, only paying for the panels and some labour to attach them to the roof? Or would this require almost as much work (and cost as much) as a completely new install?

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    Why don't you ask the companies directly? They certainly know the answer, and just asking how much their service would cost for different scenarios usually is free of charge. If you definitely want to expand your system in the future, you should consider this when it comes to sizing the transformer.
    – Erik
    Jan 3, 2020 at 10:06
  • @Erik - I'm looking for expert advice from people that maybe have been through this scenario before. A lot of companies will promise the world when it comes to trying to make the sale, I cannot trust that they will give unbiased and honest advice. I certainly don't want to put $5k down to find out a year or two down the track that they lied to my face.
    – Robotnik
    Jan 3, 2020 at 10:19
  • @Erik I also currently don't know the pros and cons of the various systems they offer. What if the one they offer to install becomes 'obsoleted' after a year, does that make the particular panels I'd need to use with that system harder to find? (Is this even a problem in the solar space? I dunno, this is all new to me!) :)
    – Robotnik
    Jan 3, 2020 at 10:24

1 Answer 1


I doubt that it will make sense to extend next year: the cost of getting somebody on site and setting up scaffolding is a significant factor.

The inverter, which converts the direct current generated by the solar panels into alternating current for your appliances and the grid needs to be suitable for the final size of your system. Having lots of small inverters, one added each year, would be costly and inefficient.

I think you would be better advised to either save up for a few years or buy shares in field-scale solar installations in the your area.

You can get an idea of prices for the hardware in the UK from the Solar Shop (e.g. you can buy 5.5kWp of panels for just over £3000). Having them installed and adding inverter and other additional items will more than double the cost (e.g. £6000-£8000 for 4kWp according to The Eco Experts).

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