If you're considering installing solar photovoltacics (PV) the biggest factor affecting the final price, and the return on investment you will receive, is which type of solar panels to choose.
PV panels can be split into a couple of categories, most are either polycrystalline or monocrystalline, which refers to the way they are manufactured.
Polycrystalline solar panels are made up from cells which are formed from multiple silicon crystals and normally have a sparkly blue appearance.
By way of comparison, monocrystalline solar cells are made from a single silicon crystal and do not have the multiple grain boundaries which you see in polycrystalline cells. The main point here though, is that monocrystalline solar panels used to be both more expensive and more powerful than polycrystalline panels. However, due to advanced manufacturing techniques that is no longer the case and some polycrystalline solar panels are now just as efficient as their monocrystalline alternatives.
The other types of panels available are either amorphous or hybrid solar panels.
Amorphous silicon does not contain the same structure as poly or monocrystalline silicon, with atoms forming a more random network which is less effective at absorbing energy from daylight. The advantages of amorphous silicon however, are that it can be deposited onto a substrate at low temperatures, making it possible to produce solar panels on glass and even on flexible plastic. The little solar strip on a calculator is made from amorphous silicon. Whilst amorphous silicon increases the range of applications for photovoltaics they are not as efficient as poly or monocrystalline products.
Hybrid solar panels consist of a combination of the above types of silicon.
For example, Sayno HIT panels use monocrystalline silicon wafer surrounded by ultra-thin amorphous silicon layers to capture more energy and generate the maximum yield from a small area.
In summary, if you are choosing solar photovoltaics for a house in the UK your best option, to get the maximum power from a limited roof space, are hybrid solar panels.
Monocrystalline and polycrystalline solar panels are a close second, and you should compare the efficiency of these closely against the price and the warranty before deciding.
Finally, if you are looking for a cheaper alternative, especially where roof space is not an issue, amorphous solar may be a good solution because although these products are less efficient they are also less expensive.