Comparing quotes that look nothing alike

You have three quotes. One is £9,000, one is £13,500, one is £16,000. They are for different equipment, they promise different savings, and only one of them mentions your radiators.

The instinct is to pick the middle one. Three steps will tell you more than that.

First, make them the same job

Nine times out of ten the difference is in what each quote includes.

Go through each quote and list what is in it. Then look at what is in one and not another. The usual culprits:

• Radiators. One quote changes six, one changes two, one changes none. This is by far the commonest reason heat pump quotes differ, and the cheapest quote is very often the one that has quietly left the radiators to you.
• Scaffolding. Often hundreds of pounds, and routinely left out of solar quotes.
• Electrical work. An older house may need a consumer unit change or a supply upgrade.
• The cylinder. Whether a new one is included, and whether it is a proper heat pump cylinder or a reused one.
• Making good. Plastering, decorating, and lifting and relaying floors are often not included.
• Removing the old system and capping off the gas.

Write the missing items into the cheap quote at a guessed price. Now compare. The gap usually shrinks a lot, and sometimes reverses.

Second, compare like with like on the numbers

For solar, divide the annual generation by the number of kilowatts of panels. That removes system size from the comparison and shows you whether the two are estimating the same roof the same way.

You should get something in the region of 750 to 1,000 depending on where you live and which way the roof faces. If one quote comes out at 1,150, it has assumed something the others have not — usually that there is no shading.

Then check the generation figure for yourself with the output calculator, using the same capacity, pitch and direction. It should land close. If one quote is well above it, ask what it assumed.

For heat pumps, compare the design flow temperatures. Two systems at the same price, one designed at 45 degrees and one at 55, are not the same purchase. The 55-degree one will cost noticeably more to run every year you own it, and over twenty years that difference dwarfs any sensible difference in the installed price.

If one quote does not state a flow temperature, you cannot make this comparison, which is itself informative.

Third, ignore their savings figures and work out your own

Quoted savings are not comparable, because each one rests on assumptions the quote does not state: what you pay for electricity, what you pay for gas, how much of your solar you use, how efficient the system will be.

Do it once yourself with your own prices, using the solar or heat pump calculator, and then apply the same figure to all three quotes. You are not trying to be precise. You are trying to compare three prices against one saving, not three prices against three different savings.

What a big difference usually is

In rough order of likelihood:

Different scope. Covered above, and the first thing to check.

A different sized system. For solar, count the panels and check the wattage. Twelve 440 W panels and twelve 400 W panels differ by nine per cent before anything else. For heat pumps, an oversized machine costs more and runs worse, so a bigger number is not a better deal.

Equipment. Real, but usually smaller than people assume. The difference between a good panel and a premium one is a few per cent of output. The difference between a well-designed system and a badly-designed one is thirty per cent of the running cost, so good design makes more difference than premium kit, and it costs less.

Optimism. A quote that promises more generation, or more saving, on the same roof has assumed something the others have not. The higher figure is coming from the assumption, so ask what it is.

Margin. It does exist, and companies are entitled to it, but it is rarely the main thing separating two quotes.

Should you take the cheapest?

Sometimes, once you have made the three quotes the same job. Often the cheapest quote turns out not to be a quote for what you want.

What is worth paying more for: a proper survey and a design you can read; radiators sized so the system runs cool; somebody who told you something inconvenient; clear answers about what is not included.

What is rarely worth paying more for: premium panel brands; a bigger heat pump than the calculation supports; monitoring apps; extended warranties on things that seldom fail.

If two are genuinely close

Then it comes down to the things a quotation cannot tell you. Did they turn up when they said they would? Did they answer questions or deflect them? Did they look at your radiators, or at their tablet? Are they local enough to come back when something needs adjusting in the second winter — because something usually does?

That last one is worth more than most line items on the page.