Most people apply for heat pump grants without understanding the deadlines. Then they panic when their voucher expires. Don’t be like most people.
The UK offers multiple grant schemes with different timelines, and missing a deadline doesn’t just delay your installation, it can cost you £7,500. Here’s what actually matters.
The Two Validity Periods You Need to Know
Heat pump grants work on two separate timelines. Get confused about which is which, and you’ll waste weeks reapplying.
Scheme-level validity determines how long the government offers funding. Voucher-level validity determines how long you have to complete your installation once approved. Both run simultaneously, but only the voucher deadline will actually catch you out.
Think of it this way: the scheme deadline is the store’s closing time. The voucher deadline is when your parking meter runs out while you’re still shopping.
How Long Does the Boiler Upgrade Scheme Run?
The Boiler Upgrade Scheme (BUS) provides £7,500 for air source and ground source heat pumps. It runs until March 31, 2028.
Originally scheduled to end in 2025, the government extended it by three years in December 2023. That sounds generous. It isn’t, because the real pressure comes from voucher validity, not scheme availability.
What About Your Actual Voucher?
Once Ofgem issues your voucher, you’re racing against tighter deadlines:
| System Type | Voucher Validity | Typical Installation Time |
| Air source heat pump | 3 months | 4-5 weeks |
| Ground source heat pump | 6 months | 12-16 weeks |
Notice something? Ground source systems take three times longer to install but only get double the voucher validity. The math barely works.
These periods aren’t suggestions. They’re hard stops. Ofgem enforces them to keep vouchers cycling through the system efficiently and prevent hoarding when budgets are capped.
Why Your Timeline Is Tighter Than You Think
Can you actually install an air source heat pump in three months? Technically, yes. Realistically? You’re cutting it close.
Most installers apply for your voucher about three weeks before your scheduled installation. Smart move, it maximises your working window. But it also means any delay compounds immediately.
Your installer gets busy. Push your date back two weeks. Installation hits a snag. Add another week. MCS certification finds a non-conformity. There go another ten days. Suddenly, your three-month voucher has two weeks left, and your system isn’t commissioned.
The full sequence looks like this:
- Installer submits application (2-3 weeks for Ofgem processing)
- Voucher issued (clock starts)
- Installation completed (4-16 weeks)
- System commissioned to MCS standards
- Certificate generated
- Installer redeems voucher with Ofgem
Ground source installations face even worse odds. Sixteen weeks for installation plus up to three weeks for commissioning, leaves a minimal buffer in a six-month window.
What Happens When You Miss the Deadline?
You reapply. Simple, right? Wrong. You return to the back of Ofgem’s queue, and your new application depends on available budget. During busy periods, particularly late in the scheme year (April to March), funding can run dry.
Miss your voucher deadline near the end of a budget year, and you might not get funded at all before the scheme closes. That’s not a delay. That’s £7,500 evaporating.
The ECO4 Scheme: Why You Need to Move Now
Eligible for the Energy Company Obligation 4 (ECO4) scheme? Then your deadline is March 31, 2026, less than three months away.
Unlike BUS, which runs through 2028, ECO4 has no extension planned. No replacement scheme announced. No guarantee of future funding. If you qualify for ECO4, waiting is the worst decision you can make.
ECO4 covers broader home improvements for lower-income households, including heat pumps. Once it closes, that pathway disappears. The government hasn’t confirmed what, if anything, replaces it.
The 120-Day Redemption Rule Nobody Mentions
Here’s a deadline that catches installers more than homeowners: your installer has 120 days maximum from commissioning to submit your voucher redemption to Ofgem.
What does that mean for you? You can’t commission your system in June and apply for the grant in October. The voucher must be redeemed within four months of commissioning, or the funding is void.
This rule prevents fraud and stops people claiming grants retroactively. For practical purposes, your installer should begin redemption immediately after commissioning, not “when they get around to it.”
How to Actually Protect Your Funding
Want to avoid becoming a reapplication statistic? Follow this instead of hoping for the best.
Get your paperwork sorted first. Your Energy Performance Certificate (EPC) must be current and demonstrate adequate insulation standards (unless your property is listed or in a conservation area). Missing documentation eats into your voucher validity period while you scramble to comply.
Ask your installer when they’ll request your voucher. Too early and you’re burning validity time waiting for installation. Too late and you’re installing on a rushed schedule with no buffer for problems. Good installers apply strategically, usually three weeks before scheduled installation.
Understand commissioning lead times. During peak seasons, MCS commissioning visits can have three-week wait times. Factor this in. Some installers recommend allowing 7-8 weeks post-installation for commissioning and certification. That leaves almost no buffer on a three-month voucher.
For ECO4, apply immediately. With the scheme ending March 31, 2026, you’re already behind. Installer schedules fill fast as deadlines approach, and local funding allocations can exhaust early.
Know your reapplication rights exist, but they’re not a plan. Yes, you can reapply if your voucher expires. No, you shouldn’t count on it working out. You’re competing for whatever budget remains.
The Bottom Line
The Boiler Upgrade Scheme, running until 2028, sounds reassuring. It shouldn’t be. The scheme deadline isn’t your problem. The voucher validity periods, 3 and 6 months, are firm, non-negotiable, and non-extendable. These are the deadlines that will actually cost you money.
Understanding this distinction separates people who get funded from people who reapply twice and give up. The scheme won’t disappear tomorrow, but once your voucher is issued, the clock starts ticking immediately.
Work with your installer to map the full timeline, especially if you’re planning upgrades linked to the best heat pumps, as availability and installation slots matter. Stay ahead of documentation requirements. If you’re ECO4-eligible, stop reading and apply now.
