Solar PV power

Why install solar panels?

How easy are solar panels to install?

What will solar panels cost?

How much power will they provide? What savings / earnings will I make?

How big an array should I install?

Do I need planning permission?

What about the the impact on my house value?

What about the climate impact / carbon payback?

Other types of solar panes/renewables

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Why install solar PV panels?

1. Solar power is the cheapest energy source in the world, after huge drops in panel prices, and is popular and affordable even in the poorest countries. In the UK, new electricity export tariffs mean that you can make money on solar. A typical 4kW array might cost £6,000 to install, and make/save you £900 a year in two ways: reducing how much electricity you have to buy in or "import", and giving you spare energy to sell or "export. It's this export bit that gets your energy from a big cost down to net zero or even net income.

2. Solar power is super green. It's the major way we get to net zero carbon emissions, and cheaply too. The panels are silent and last for decades, and are practical and affordable for the majority of homes. There are already about 1.5m homes with solar in the UK, and record ongoing installation levels.

 

How easy are solar panels to install?

If you have a south, east or west facing roof then you can install solar panels - though south and west are the most cost effective, because they generate more power at times of day when power prices are higher.

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Solar PV panels are normally attached to rails which are fixed to the roof. The fixings pass between the tiles, and an array can normally be installed in one day. You will need scaffolding in most cases, though installers may be able to use just a portable tower if installing on a bungalow or garage, which will reduce costs.

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A cable runs into the roof and to a vital device called an inverter, which changes the direct current (DC) generated by the panels into alternating current (AC) which is used by the grid and all your house appliances. If you want a battery as well it's a good idea to install this at the same time as the battery and solar array can share the same inverter, and it's a particular type called a hybrid inverter which works for both. If you don't plan a battery but think you might in future, ask about getting a hybrid inverter for your solar to "future-proof" you for a future battery.

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You can install on a flat roof too, normally using weighted frames which sit steady on the flat roof under their own weight, holding their panels at the right angle to the sun. The panels on many flat roofs may be invisible from the ground if they are behind a parapet, which may help if appearance is a concern, eg in a conservation area.

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You do need to own your own home. If you own a flat, you'll need you'll need to get agreement from the freeholder. 

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What will solar panels cost?​

A typical 4kW array might cost £6,000 to install, and make/save you £900 a year in two ways: reducing how much electricity you have to buy in or "import", and giving you spare energy to sell or "export. It's this export bit that gets your energy from a big cost down to net zero or even net income. There is no VAT  on solar panels or installation costs.

Costs might comprise: panels themselves say £1200; the inverter to convert DC power to AC for your home £5-800; scaffolding £1000 and labour to install £3000. If you install on single storey you should avoid scaffolding costs. The releatively low panel price vs fixed labour/scaffolding costs mean that you get economies of scale if you put in a larger array, getting more back per £ invested.

 

How much power will they provide? What savings / earnings will I make?

You make money from solar in two ways: generating free electricity for your own use which you then don't have to pay for. and exporting to the grid, for which you get paid. If you use most of your PV power yourself, you will save more from the cut in your electricity bill than from exporting. But if you use less electricity then you may well make more from exporting (and you will of course be better off overall). The arrival of high export tariffs, most notably from Octopus Energy, paying 15p/kWh exported, has massively improved the financial returns you can make from solar panels. 

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For example, our original 4kW solar array in the South of England generates about 4000kWh per year. With standard use (ie not heating or EV)  we used about 1000kWh of that ourselves, and paid for another 1100kWh from the grid. We therefore exported 3000kWh which earned us £600, while the grid power only cost us about £330 - net negative! [prices 2023]. To work out the return on investment, we can add to the £600 the 1000kWh we didn't have to pay for, which would have cost about £300. So we gained £900 per year from an investment of £7000. That's a 7.7 year payback or 13% return on investment. (and installation prices have dropped since then). There are no grants or subsidies for solar PV. 

 

You can work out how much power will be produced from your proposed panels using online calculators like the Energy Saving Trust and Spirit Solar. These do a good job of working out the solar energy for your geographical location and orientation, but shading is more difficult to assess. The best thing is to look at your chosen roof in the sun at different times of the day/year to see if it is shaded by buildings or trees. You need to check all seasons as the sun is much lower in winter than summer. A little shading for an hour or so is no problem, but if most of the area is shaded in the middle of the day in summer, then you may have to think again. If you can't wait a whole year to check on the sun in the different seasons,  try an astronomy app like Google Skymap which will show you where the sun will be on different dates/times.

 

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Be aware that shading just a small part of the PV array can shut down most of the output - that's just the way the electronics work. If you're likely to have part of the array shaded then talk to your installer about fitting optimisers or string inverters which make PV work better with partial shading. 

* of course, make sure you check the latest export tariffs available so you know what your earnings may be, and realise that these tariffs are not guaranteed and could be withdrawn. As we've seen, import and export tariffs can change unexpectedly, but if you have solar, and especially if you are a net exporter, you will be more protected from high electricity prices than if you don't.

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How big an array should I install?

How big is your roof?! As long as solar is generating returns above 10% as in the example above, you may want to install the biggest array you can afford. Solar PV is likely to be the best earner of all the measures we discuss on this site, and relatively simple and non-disruptive in practical terms, so where possible go large*.

 

The most common array size is around 4-5kW, or 10-12 panels. Note that to achieve net zero, you may need a slightly bigger array than this, eg 6kW. This will be no problem on a larger roof, but might be a tight fit for smaller homes or those with difficult roof lines, dormers, Velux etc. Consider if you can fit extra panels on a garage or in the garden.

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Do I need planning permission?

You don't need planning permission in the UK unless you have a historic listed house, or live in a conservation area. In these cases you may need planning permission, and you may not be able to install on the main house roof if it affects the appearance of a historic house or conservation area. Often however you can install them on a garage or outhouse, or if you have land you can install in a field or big garden, on the ground. This may be cheaper as no scaffolding or roof work is required.

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How does PV affect house value?

So - would you pay more for a house with solar panels, or think them an eyesore? This question was asked a lot in the early days of solar in the 2010s, before PV became more common, and new power tariffs enabled solar to make serious money for the homeowner. With solar panels able to make you around £1000 per year better off, they have clear value when you sell.

That said, it's always good to do the best for your house's appearance. Pay attention to the panel layout on the roof - some approaches look more attractive than others. Normally, a symmetrical layout looks better, and you'll be able to choose which you prefer from a range of different panel designs.

Panels are of course normally rectangular, and this does not always fit beautifully if you have a hipped roof with diagonals. Triangular panels are available, but expensive, and may not match your house angles - they are very rare in practice.

In the end if you had a weird potential buyer who didn't like solar, it would only cost about £1000 to remove them, which is trivial in a house sale.

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What about the climate impact / carbon payback?

Every kWh you generate with solar displaces a kWh from the grid, and results in fossil power being turned down or off (so long as you don't increase your consumption just because you have solar). In fact your carbon footprint from electricity may well be net negative - in other words the world is better off than if you and your home didn't exist at all!

There is of course a climate impact in manufacturing PV panels. One common and simple way of working out the carbon costs and benefits is through the carbon payback calculation - what is the impact of producing a panel, and how long does it take to displace enough fossil electricity to make up for this? This calculation has been done for many panel types and markets. To use our Sunpower panels as examples, their production impact is quoted at 300g/W  in Table 3 here. Our 3.9kW of panels therefore involved 1.17t CO2e. They generate 4000kWh pa displacing gas generation which would otherwise emit 360g/kWh, so that saves 1.4t CO2e pa. The panels therefore make up for their manufacture in 10 months. (even quicker if you assume coal generation displaced).

Also, manufacturing impact is improving all the time, especially as the PV factories themselves use PV.

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Other types of solar panel or renewables

You are probably aware of solar thermal panels which generate hot water directly. An installation of this kind is much smaller than PV, often only a couple of panels worth, and needs plumbing and hot water storage. Solar thermal has been available longer than PV, but has lost out to PV in popularity as it is more complex and generates more modest savings. In particular, a PV array can heat your water very easily using an immersion controller like iBoost or, more efficiently, via a heat pump, so why bother with solar thermal?

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You may also come across a thermodynamic panel. This is a kind of hybrid of heat pump and solar thermal, used only for hot water. It collects solar warmth on a smallish panel and this is then shifted with a compressor heat pump style to your hot water tank. It may therefore be more effective than solar thermal alone, but with a price tag of several thousand pounds it's hard to see the advantage over a proper PV array which may not cost much more. These thermodynamic panels have also been, in our experience, the subject of doorstep hard selling tactics, which is offputting. However, we don't have first hand experience of them and would love to hear from any of you who have.

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It is technically possible to install a wind turbine or hydro, but these are rare and normally only for big land owners or those in relatively isolated homes. There was a brief flurry of interest in micro wind turbines (<2kW) in the 2010s, with David Cameron fitting one as a publicity stunt, and DIY chains stocking them. But they have been found to have quite low outputs when installed on houses, especially in urban areas, due to turbulent wind currents around houses and trees. The load factor (energy generated vs rated max capacity) may only be around 10%, (vs 50% for big offshore turbines). This makes them less effective than solar PV and means they are rare in practice in urban or village locations.

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Larger wind turbines of say 6kW are commonly in use on farms and anywhere where there is unobstructed wind flow and it's practical and permitted to erect, given the typical height is 6-10m. They are normally mounted on poles and offer the potential for significant energy generation, which unlike solar continues at night and is highest in the winter. In fact a wind/solar combination with batteries offers the potential for completely off grid living. We recently passed an isolated cottage at the top of a lock in the western highlands of Scotland, with a turbine taking full advantage of the massive wind funnelled up the loch - the perfect location.

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Perhaps surprisingly, planning permission is not required for one small/micro wind turbine, whether pole or building mounted, so long as it meets MCS requirements. But - get this - if you already have a heat pump, you will need planning permission! This is to do with multiple noise sources, but is really out of date now that modern heat pumps are so much quieter.

Care needs to be taken regarding noise, as this type of turbine can make a noticeable sound - relatively more than a large grid turbine. They are therefore not normally mounted on, or even near houses, with the occasional exception of large tower blocks.

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Hydro power naturally requires you to own or have the rights to a significant stream or river, and to be most effective requires a dam as well to increase water pressure and provide storage over summer. Again, one for big land owners.