Last year an automotive parts manufacturer asked us for solar with battery storage on a 110-kW system. They were ready to buy the battery. We told them not to.
Their half-hourly data showed a site that ran hard through the day and went almost dark by early evening. Solar would cover the daytime load directly. A battery would have charged on surplus that barely existed and discharged into demand that was not there. It added cost, stretched the payback and delivered very little. We recommended solar only, and that is what went in.
We have sat on the other side of that table too, sizing storage for sites that plainly needed it, where the engineering took days and the client’s approval process took weeks. That ratio, days of engineering against weeks of finance, describes the UK commercial storage market better than any technology roadmap does. And it shows up in our own completed work more sharply than I expected.
What Our Installations Look Like When You Sort Them by Value
We took every installation we have completed since February 2021, 2,610 jobs in all, grouped them by invoice value and checked which specifications included storage.
In the £10,000 to £20,000 band, mainstream residential, a homeowner deciding at a kitchen table, 1,123 of 1,230 jobs included a battery. That is 91.3%. (Editor’s note: One pound = $1.33 as of September 23, 2026).
Between £20,000 and £30,000 it falls to 55.9%, 19 jobs out of 34. Above £30,000, commercial and multi-dwelling scale, it falls to 12.5%. Two jobs out of 16.
Those three bands cover 1,280 jobs. The rest of the book sits below £10,000, where system sizes are small enough that the storage decision is a different question, and I have left it out rather than flatten it into the same comparison.
The top band is worth describing, because it is not marginal work. It contains 50-kW three phase systems on sites in Harrow, Ipswich, Greenford, Bristol, Wolverhampton and Birmingham, running between 100 and 177 modules each. Every one of them went in solar only.
Two caveats before anyone builds a market thesis on this. Sixteen projects is a small sample, and this is one installer’s order book rather than a national survey. And it records completed installations only, so it shows storage disappearing from the specification as project value rises, not how many storage projects were killed outright. We cannot see the ones that died.
But the direction is not subtle, and the same engineers designed both ends of it.
The Mechanism is Regulatory, and it is Four Years Old
The comfortable explanation is that commercial buyers are more conservative than homeowners. The real explanation is that the two markets are paid by completely different mechanisms, and only one of them still works.
Residential storage in the UK is underwritten by import arbitrage. A domestic smart tariff prices overnight electricity at around 8p per kWh against a capped day rate of 26.32p from 1 October. Charge overnight, discharge across the day, and the saving per unit is large, predictable, and requires no heroic assumptions about how the household behaves. That case has strengthened every year since 2022.
Commercial storage used to be underwritten by Triad avoidance. Ofgem’s Targeted Charging Review ended it. The residual element of transmission charges, which is around 90% of TNUoS, became a fixed daily charge tied to available supply capacity rather than something a site could avoid by managing demand. The Triad benefit itself was removed from April 2022, after a final Triad season over winter 2021/22. Discharging a battery across the three winter half hours that used to define a site’s transmission bill no longer reduces it. Businesses that had built load shifting or on-site generation strategies specifically around Triad periods lost that value outright.
What remains is real but harder to sell. DUoS red, amber and green consumption rates still apply on a time of use basis, so red band avoidance still pays. Self consumption of on-site generation still pays. Resilience still has value. But none of those three produces the single clean figure that Triad avoidance did, and two of them cannot be modelled properly without half-hourly consumption data the client often does not have to hand.
So the finance team is not being timid. They are being handed a business case whose strongest line item was deleted by a regulatory change four years ago and which, as an industry, we have not rebuilt. Solar clears the hurdle rate on its own. Storage is the line that gets cut to make the number work.
Our own data cannot prove that causation. Sixteen large projects, straddling both sides of the change, is nowhere near enough to test it. I offer it as the most plausible reading of a gap we can see clearly and have not been able to close.
Where the Data Said No, and Where We Were Too Slow
The auto parts job was a case where the data said no and we listened. The one that still bothers me went the other way.
A residential care operator in the East Midlands runs 24 hours a day. People live there. Demand is flat, overnight load is real, and resilience is not a comfort argument. That is the textbook site for storage, and we knew it.
We installed solar first and left the battery out. The solar case cleared on its own. The combined case did not clear the first pass, and the client wanted to see real numbers before committing more. After 14 months of live generation data against actual consumption they came back, and we added the battery as a second phase. It is now doing what it should have been doing from the start.
The battery was right for that site on day one. Splitting it into two phases cost the client more than a year of savings and cost us a second mobilization. We did it because a single combined proposal did not survive their approval process, and instead of rebuilding the case, we cut the line. That is the pattern this whole article is about, and we are not exempt from it.
What would actually change it? Three things, none of them glamorous. Stop quoting storage as an accessory to a solar array. Size it against the site’s half hourly demand profile and its red band exposure, and quote it as a separate line with its own business case. A battery sized to soak up solar export is solving the installer’s problem, not the client’s.
Put the outage cost on the paper. In residential, resilience is a comfort argument. On a production line it is a number: lost output per hour, spoiled work in progress, restart time, and it is usually the largest figure in the room. It rarely appears in the proposal because installers do not ask for it and clients do not volunteer it.
Be honest about what the TCR removed. Business cases still circulating with Triad avoidance in them are wrong, and every one that gets found out makes the next proposal harder for everybody selling into this market.
The technology curve is not the constraint here and has not been for some time. The constraint is that the commercial storage business case was written for a charging regime that no longer exists. Until the industry rewrites it, that 12.5% is not going to move.
—Manan Shah is co-founder of Solar4Good, an MCS-certified solar and battery storage installer with more than 3,000 residential and commercial installations across the UK.
