Attacking the Thermal 70%: Heat Pumps & Solar for Breweries

Any installer who tells you solar panels will wipe out your brewery’s energy bill either does not understand brewing or is hoping you don’t. The uncomfortable truth is that roughly 70% of the energy a brewery uses is thermal, the wort boil, the hot liquor tank, steam raising, CIP wash cycles, and a solar array produces electricity, not heat. Photovoltaics cannot directly touch that 70%. The remaining ~30% is electrical, and that is where PV pays first.

This post is about the harder, more interesting question: once you have captured the electrical load, how do you actually attack the thermal 70%? The honest answer is a layered one, heat recovery first, then PV surplus into the hot liquor tank, then an industrial heat pump doing the heavy lifting, ideally running on your own solar electricity. None of it is a silver bullet. All of it is margin defence in a sector losing roughly three breweries a week.

Why PV alone cannot touch the boil

The wort boil needs energy delivered as heat, at around 100°C, in a short, intense burst. A solar array gives you electrons at ambient temperature. There is no direct route from one to the other that does not involve a conversion step, and every conversion step has a cost and an efficiency.

Your thermal demand is dominated by a handful of processes: raising the hot liquor tank to strike temperature, the rolling boil in the kettle, steam for the mash and for cleaning, and hot CIP for tanks and lines. These are gas or steam jobs today in most breweries. A 50kWp array on the roof does nothing for any of them on its own. That is the honesty this whole site is built on, and it is exactly why we frame solar as one tool in a resilience strategy, not a green magic wand.

So the sequence matters. Get the electrical load right first, then use whatever you can spare, surplus electricity, waste heat, clever kit, to chip away at the thermal side.

Where PV earns its keep first: the electrical 30%

Before we spend a penny electrifying heat, capture the electrical load, because that is where solar is genuinely excellent. Refrigeration and glycol chilling is around 35% of a brewery’s electricity and runs 24/7 through fermentation, which is why a well-sized brewery array typically self-consumes 75–90% of what it generates, you are producing power exactly when your fermentation cellar is drawing it. Packaging (~25%), compressed air (15–25%), pumps (15–20%) and lighting (8–12%) make up the rest.

At roughly 8–16 kWh of electricity per hectolitre (higher for nano and craft sites), a UK yield of about 850 kWh per kWp per year and around 6 m² of roof per kWp, most breweries can cover a large slice of that electrical demand. Work the numbers on our savings calculator and the sector-by-sector detail in sizing solar for a brewery. The economics of self-consumption are what make everything downstream possible: importing costs around 25p/kWh (large half-hourly sites 15–24p), while exporting under the Smart Export Guarantee earns only a 12–16p range, Octopus cut its rate to 12p on 1 March 2026. Every kWh you keep on site is worth far more than one you sell.

That gap is the whole argument for redirecting surplus into heat rather than dumping it to the grid.

Route 1: PV surplus into the hot liquor tank

The simplest thermal win is a solar diverter feeding an immersion element in the hot liquor tank. When your array is generating more than the brewery is using, a summer afternoon with the chiller satisfied, instead of exporting that surplus at 12–16p, you divert it to an immersion heater and pre-heat your liquor for the next brew.

Be clear-eyed about what this does and does not do. It is a COP of 1, one kWh in, one kWh of heat out, so it is not efficient in the way a heat pump is. It only reaches modest pre-heat temperatures, and it only works when you have genuine surplus. It will not run your boil.

Where it shines is when export is constrained. Many brewery connections use G100 export limitation to keep within what the network can accept (more on the grid side in G99 grid connection for brewery solar). If your surplus would otherwise be curtailed and thrown away, diverting it into the HLT is free heat, pure gain. It is cheap, it is simple, and it displaces gas at the pre-heat stage. Just don’t oversell it to yourself.

Route 2: industrial heat pumps, the real thermal lever

This is where you genuinely start to move the 70%. An industrial heat pump upgrades low-grade heat, ambient air, waste heat off your refrigeration plant, warm effluent, to useful process temperatures. Because it moves heat rather than creating it, it delivers a coefficient of performance (COP) of roughly 2.5–3.5: each kWh of electricity becomes 2.5–3.5 kWh of heat.

Now connect that to your solar array. A heat pump running on your own PV turns one solar kWh, which would otherwise export at 12–16p, into 2.5–3.5 kWh of heat displacing gas. That is a dramatically better use of surplus generation than an immersion element, and it is the single strongest reason to think about PV and thermal together rather than separately.

For the boil itself, the hottest, hardest load, standard heat pumps run out of temperature. The tool there is mechanical vapour recompression (MVR), which recompresses the vapour coming off the kettle and reuses its latent heat to sustain the boil. Vapour-recompression systems achieve effective COPs well above a conventional heat pump, which is why they are the technology of choice for attacking wort-boil energy directly.

The honest caveats: heat pumps and MVR are capital projects, they use refrigerants that bring F-gas obligations (the same regime that governs your existing glycol plant), and the temperature match to each process has to be engineered properly. But if you are serious about the thermal 70%, this is the lever. There is a genuine tax and compliance angle too, self-generated on-site solar sits outside the Climate Change Levy entirely, so electrifying heat and running it on your own generation can take that load out of CCL, over and above any Climate Change Agreement relief your brewery qualifies for.

Route 3: heat recovery, do the cheapest kWh first

Before you electrify anything, recover what you are already throwing away. The cheapest kWh of heat is the one you don’t have to make twice.

A vapour condenser on the kettle captures the energy in the boil-off and uses it to pre-heat the next batch’s liquor. Waste heat off the refrigeration and glycol plant, which you are currently rejecting to atmosphere, can pre-heat wash water and CIP. These measures often have the shortest paybacks of anything on this page, and crucially they shrink the thermal load before you try to electrify it, so every downstream investment is smaller. Adnams in Southwold is a well-known example of a brewery pairing PV with a serious thermal strategy; Stewart Brewing in Edinburgh runs a 210kW array against its electrical base. These are illustrative third-party projects, not our clients, but they show the layered approach working in practice.

The order of attack

Sequence beats spending. In order of value:

1. Heat recovery, vapour condenser and refrigeration waste-heat capture. Cheapest kWh, shrinks the load.
2. PV for the electrical 30%, size it to your refrigeration base for 75–90% self-consumption. See is solar worth it for a brewery.
3. Surplus into the HLT, a diverter and immersion for otherwise-curtailed generation.
4. Heat pump / MVR on the residual thermal load, run on solar wherever possible, to multiply every kWh 2.5–3.5×.

Do it in that order and each step makes the next one cheaper. This is craft-scale engineering as much as it is a national-brewery play, the same logic applies to a craft microbrewery as to a regional site, just at different capacities.

Common questions

Can solar panels power my wort boil?

Not directly. PV produces electricity; the boil needs heat at ~100°C. You reach the boil through mechanical vapour recompression or an industrial heat pump, kit that can be powered by your solar surplus, which is the connection that matters.

Is an immersion diverter worth it if I can already export?

Marginally, if your export rate is healthy, exporting at 12–16p can beat displacing gas at a COP of 1. It becomes clearly worthwhile when G100 limits your export, because then the surplus would otherwise be curtailed and wasted.

How much of my 70% thermal load can a heat pump realistically cover?

It depends on your process temperatures and available low-grade heat, so it needs a proper engineering assessment. Conventional heat pumps handle pre-heat and CIP well; the boil itself is an MVR job. Model your numbers on our cost page first.

What’s the single best first move?

Heat recovery. Recovering boil vapour and refrigeration waste heat is usually the cheapest kWh in the building and it shrinks everything downstream. Request a quote and we will size the electrical array and map the thermal route together.

For the policy detail behind the export figures and the levy treatment, see Ofgem’s Smart Export Guarantee and the government’s Climate Change Agreements guidance.