All you can heat
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All you can heat

Let’s talk about efficiency (even more)

Hello and welcome to All You Can Heat, a new place for Nesta’s Sustainable Future team to share extra analysis and ideas from our work on home heating and energy. This will be a place to share new ideas and emerging thoughts on some of the biggest issues in heating, so please do join the discussion, tell us what we’re getting wrong and hopefully challenge your own thinking in the process.


We need to talk about efficiency. We now live in an era of energy scarcity, and we must use as little energy as possible. Efficiency is especially important in home heating, given how much gas we burn in our homes and how much electricity we will need to use for it in future. The more efficient we are, the less gas we’ll need to import, or the less electricity we’ll need to generate.

The efficiency challenge applies to any new heating technologies — hydrogen, boilers, infrared. It’s the first question I ask when someone tells me about a technology I haven’t heard of — how efficient is it? But it applies to heat pumps and to gas, too. In a time of spiralling bills and fuel poverty, we need to focus on efficiency in all its forms.

When people talk about energy efficiency in homes, they mainly mean insulation. This is something we need to gently challenge — not to say insulation is bad, but that heating systems need to be efficient too. Insulation is important when cost effective and well installed, but it is not the only way to reduce energy use. Making a boiler run more efficiently is energy efficiency; the Heating Hub’s campaign on turning down boiler flow temperatures is so important, and we are working with Jo Alsop to help major heating organisations adopt the message.

Heat pumps are an energy efficiency measure too. If you switch to a heating system that uses three to four times less energy for the same heat, that is a huge increase in efficiency, no matter what your EPC certificate says. It’s hard to think of any other field where you have a technology that’s three or four times more efficient than alternatives.

But there’s also more to efficiency than just arguing about specific heat sources. One of the things that’s becoming more obvious to us is that heating a home is not just about the heat pump, the boiler, or whatever the heat source is. Heating is a system that covers the whole home. Radiators, pipes, storage, fabric, insulation, controls, meters. What matters more than anything else is to make this whole system efficient. You could put the world’s most efficient heat pump into a home that has the wrong radiators and it will not be very efficient. Same if the residents don’t know how to use their heating controls. The heating source is important, but it needs to be part of a well-installed system.

When we talk about heat pumps, it’s really shorthand for heat pump systems — the whole package of stuff that goes into a home. This is old news to most installers. We’re pretty confident that, in most homes, most of the cost of a heat pump isn’t the heat pump unit itself, it’s installing the whole system properly. If the job was just to bolt a heat pump on to the side of a house, it would be cheap and easy. From heat loss surveys to hot water tanks and sometimes pipes and radiators, installations are a complex, whole-home job.

Madeleine Gabriel and I were at the Utility Week Future of Heat conference last week, and so much of the debate was the usual heat pumps versus hydrogen (though a notable exception was an excellent presentation on heat networks by Jacob Byskov Kristensen from Denmark). These technology arguments are frustrating for many reasons (no wonder customers find heating confusing!), but in particular because they stop us focusing on home and heating systems. It would be nice if we could start using technologies together, rather than pitching them as alternatives to each other. Storage is clearly going to be a vital part of home heating systems in the future. Infrared panels may have a role in topping up more efficient heating systems on particularly cold days. Direct electric hot water systems could complement air-to-air heat pumps in some buildings.

The efficiency argument is one we need to apply relentlessly to claims of silver bullet technologies that can decarbonise home heating easily. How efficient is your technology really? Is it going to save households money on their bills? And it would be great to see some kind of recourse for customers who end up left with inefficient heating systems and eye-watering bills. There are likely to be some poor heating systems installed over the coming years, and we should have a way to help people who find themselves in these situations.

I’ll finish with a question about heat pump efficiency: do we know how efficient they really are? Our analysis of MCS installation records (by my colleague Chris Williamson) showed Seasonal Coefficients of Performance (SCOPs)estimated by manufacturers rising over time, and topping four for flow temps below 40C. You can see this in the chart below.

Chart from Nesta’s report How to Reduce the Cost of Heat Pumps

But these are manufacturer estimates. We don’t know if they really achieve those kinds of average COPs when they’re installed. We think it’s likely that the best installations do, but not all installations meet that standard. We’re also unsure what Seasonal Performance Factors (SPFs) are really achieved. In our report on reducing the cost of heat pumps, we used a median SPF of 2.71 (based on in-situ monitoring data from a range of sources). That was a deliberately conservative estimate, and we’d love to increase it if we can find firmer evidence to do so. So help us please — how can we get a better estimate of real-life COPs or SPFs? Will current monitoring studies — like the BEIS and Energy Systems Catapult Electrification of Heat Demonstration project — be the best answer? What other sources might there be? And what can we do to make sure efficiency keeps rising, and that customers get proper, trustworthy information about how efficient their system is?

This is important, because whatever technologies we’re advocating for, we need to know how efficient they are and how to make them even more efficient.



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Andrew Sissons

Andrew Sissons

I write for Nesta’s All You Can Heat by day, and am writing the What Would Make Life Better? series by night. With occasional economic history thrown in too!