Why do housebuilders keep oversizing homes for the grid?
Future Homes Standard is pushing England toward all-electric new homes: heat pumps, rooftop solar, and electric vehicle charging as standard. That shift is necessary. It also makes everyone nervous about grid capacity.
The instinct is understandable. No housebuilder wants to discover late in the programme that the site cannot be connected, or that reinforcement will blow the viability case. So teams play it safe. Heat pumps are specified generously. kVA allowances per plot creep upward. DNO applications request maximum capacity upfront.
The problem is that safe often means expensive. And on many schemes, it also means wrong. We overspec the kit inside the home, especially heat pumps for space heating and hot water, and then we overspec the grid connection to match. Two layers of over-engineering, both paid for by the development.
Everyone is nervous about future demand, so we keep throwing more capacity at the problem. But smarter, flexibility-ready homes do not have to be more complicated. They need to be right-sized and grid-aware from day one.
What is wrong with blunt ADMD assumptions?
Consultants and design teams have long had to estimate electricity demand for all-electric homes based on limited data. ADMD tables and rules of thumb filled the gap. That was understandable when the housing stock and technology mix looked different.
But those assumptions are often blunt and over-cautious. They treat homes as if every heat pump, every hot water cylinder, and every EV charger will run at peak, at the same time, across the whole development. They rarely reflect how efficient fabric, smart controls, PV self-consumption, or load management change the real profile.
The Future Homes Hub guide on grid connections for all-electric houses states that most applications currently ask for too much power, too early, and that accurate load assessment and realistic load profile phasing plans are key to securing a connection as quickly and cost-effectively as possible.
ADMD is not the enemy. The issue is using it as a ceiling rather than a starting point, without testing whether the homes you are actually building perform like the homes the tables were built for. Developers and local networks have worked with rules of thumb that simply do not match how modern homes perform today.
Where does over-engineering show up on a scheme?
Over-engineering is rarely one decision. It is a chain of cautious assumptions that stack up from appraisal to DNO submission.
Inside the home, heat pumps are often sized for worst-case space heating and hot water demand with little or no diversity credit. That adds equipment cost, may affect acoustics and plant space, and feeds a higher per-dwelling import assumption upstream.
At plot level, kVA allowances are set high because no one wants to reopen the electrical strategy later. Across a 100-home masterplan, an extra 2 or 3 kVA per plot is not abstract. It flows into substation sizing, cable routes, connection offers, and programme.
At scheme level, the DNO application may request the full nameplate sum because Future Homes Standard feels like a step change. Phasing, occupancy, load-managed EV charging, and staged heat pump commissioning are treated as afterthoughts rather than core inputs.
Unnecessary cost gets added into every scheme. Worse, we can lock in grid constraints instead of helping to relieve them. Oversized connection cases can trigger reinforcement that evidence-based load profiles would not have required, tying up capacity and capital that could have served more homes elsewhere on the network.
What did HubbPro's analysis with Turley find?
HubbPro worked in partnership with Turley to combine real-world development experience with advanced data modelling. The objective was practical: show how today's all-electric homes actually perform, and what smarter design could mean for grid planning.
HubbPro's predictive tool draws on live performance data and machine learning. Rather than relying on static ADMD tables alone, it models how efficient homes with heat pumps, PV, and smart technologies use power across time. Turley brought scheme-level and sustainability perspective; HubbPro brought the performance evidence.
The study found that the average modern home needs around 35% less grid power than even the lowest industry standards assume at any one time. That is not a marginal tweak. In practice, it means a typical local substation, the kind found in most neighbourhoods, could power over 500 new homes instead of around 350 when demand is right-sized.
The wider implication is significant. The UK could build two to three times more homes using the grid infrastructure already in place, while cutting connection costs and speeding up delivery. Smaller, cheaper, and faster grid upgrades become realistic as older homes switch to low-carbon heating and transport, not just for greenfield development.
This aligns with what we see on live schemes. We have been designing for the past, not the future. Heating systems are smarter, appliances are more efficient, and residents are more aware of how to manage energy use. The data gives confidence that we can build more homes without waiting years for grid upgrades, if we are smarter, not bigger, in energy planning.
What does flexibility-ready actually mean?
Flexibility-ready does not mean every home needs a complex energy stack or exotic controls. It means the development is designed so import and export can be managed intelligently from the outset.
That includes right-sized heat pumps and hot water provision, realistic EV charging strategies rather than dumb peak loading, consideration of PV self-consumption, and connection phasing that matches how the site will actually be built and occupied.
It also means an internal conversation before assumptions embed: have we planned for flexibility-ready homes? Not as a sustainability label, but as a grid strategy question with commercial consequences.
Smarter homes do not have to be harder to deliver. They need clearer evidence behind the numbers going into the DNO application, and a willingness to challenge default kVA and ADMD inputs while there is still time to change course.
Why does this matter beyond new build?
The Turley and HubbPro findings are framed around Future Homes Standard and new development, but the logic applies more widely. As older homes are retrofitted with heat pumps, PV, batteries, and EV charging, networks face the same question: are we planning for real load profiles or for outdated peaks?
Right-sized assumptions should mean smaller, cheaper, and faster grid upgrades in existing communities too, helping accelerate the move toward a net-zero housing stock without treating every low-carbon retrofit as a worst-case demand spike.
For housebuilders, that strengthens the case for getting new-scheme assumptions right now. The homes you build today set performance expectations for the assets and networks they connect to for decades.
What practical questions should developers ask earlier?
Before the next scheme goes too far, teams should pressure-test the electrical strategy with questions like these:
- Are our ADMD assumptions based on evidence, or on default tables and rules of thumb?
- Have we right-sized heat pumps for space heating and hot water, or oversized plant that inflates grid demand?
- What kVA allowance per plot are we carrying, and what is it based on?
- Does our DNO application reflect phasing, occupancy, and load management, or a worst-case nameplate sum?
- Have we planned for flexibility-ready homes from day one?
- Could a more evidence-based connection case reduce reinforcement, cost, and programme risk?
- Are we locking in grid constraints when we could be relieving them?
These questions belong in appraisal and concept design, not after the cost plan and PoC submission. By then, the commercial and technical direction is often already fixed.
What is the real opportunity?
Future Homes Standard will make all-electric homes the norm in England. That transition is already adding cost and complexity to every pipeline scheme. Oversizing grid connections on top is an avoidable layer of pain.
The opportunity is to use real-world evidence to right-size connections, save millions on unnecessary infrastructure, and make clean, affordable energy a reality for more people. It is a practical step forward for housebuilders, homeowners, and network operators alike.
HubbPro is focused on that upstream decision point: helping teams test what right-sized and flexible could look like on their scheme before heat pump schedules, kVA tables, and DNO applications lock in the wrong answer.
If you want a practical view on what that could mean in your pipeline, reach out to HubbPro and let's talk before your next scheme goes too far.