Should you wait for better panels?

It is a reasonable instinct. Panels are more efficient every year, prices drift down, and something better is always a year away, so waiting looks sensible.

The trouble is what you are waiting with, which is a roof making nothing.

The arithmetic of waiting

Suppose a system would save you £700 a year. Every year you wait costs you that £700, and you do not get it back.

For waiting to pay, next year's system has to be more than £700 better — cheaper, or generating more, or both. Panel efficiency improves by something like half a per cent a year in absolute terms. On a system generating 3,800 units, that is a few tens of units, and prices move slowly and not always downwards.

So the gain from waiting a year is worth tens of pounds and the cost of waiting is worth hundreds, which is not a close sum.

This holds for essentially any technology that starts saving money the day it is installed. It is the opposite of buying a phone, where waiting costs you nothing but patience.

What panel efficiency means

Worth clearing up, because it is the number the waiting argument rests on and it is widely misread.

Efficiency is the share of the sunlight hitting a panel that comes out as electricity. Twenty years ago it was around 15 per cent; a good domestic panel now is around 22.

Here is the thing: efficiency mostly decides how much roof you need, not how much electricity you get. If you want 4 kilowatts of panels, you can have them at 19 per cent efficiency or 22 — the second just takes up less roof, and the electricity is the same.

Efficiency only matters when the roof is the limit. If you have a small roof and want more capacity on it, higher efficiency buys you that. If you have plenty of roof, it buys you nothing and you should not pay a premium for it.

So the annual efficiency improvement everyone points to is, for most houses, an improvement in something they were not short of.

Changes that would justify waiting

Not efficiency. Two other things could genuinely change the decision, and both are things to keep an eye on without waiting for them.

What you are paid for exported electricity. This has moved a lot over the years and it materially changes what a system is worth. It is a tariff question, not a technology one, and it can move either way.

Battery prices. These have fallen considerably and may fall further. If a battery is the part you are unsure about, that is a more reasonable thing to defer — and you can add one to an existing solar installation later, which is the good news. Fit the panels now, add storage when the sums work.

Neither of those is a reason to leave the roof bare in the meantime.

Good reasons to wait

There are some, and they have nothing to do with the panels.

Your roof needs work. If the covering is near the end of its life, do the roof first. Taking an array off and putting it back is expensive and completely avoidable.

You are about to do something that changes your consumption. An extension, an electric car, a heat pump. All of them change how much electricity you use and therefore how much solar is worth, and sizing around next year's household is better than sizing around this one.

You are moving within a couple of years. Solar adds something to a sale price but rarely all of what it cost, so a short horizon changes the sum.

You cannot afford it without borrowing badly. No saving on the bill justifies an expensive loan to get it.

A middle option

If the hesitation is uncertainty, not timing — you are not sure solar suits your household — there is now something between waiting and committing.

Plug-in panels became legal in the UK in August 2026. A few hundred pounds gets you one or two panels and a live generation figure, and a few months of watching it will tell you more about your own household's shape than any amount of further reading.

That is a genuinely sensible way to defer a decision. Deferring it in the hope that panels will be four per cent better is not.