The SAP – ECP Puzzle – Why Are Gas Boilers “A-Rated” While Electric Boilers Get a “D”?

If you’ve ever checked your home’s Energy Performance Certificate (EPC), you may have spotted something that feels completely backwards.

A gas boiler — burning fossil fuels and producing emissions — can achieve an A rating.

An electric boiler — almost 100% efficient at the point of use and producing no emissions inside your home — can end up with a D.

Naturally, people ask:

**How does that make any sense?**

The short answer: EPC ratings aren’t always measuring what people think they are.

The EPC Problem Nobody Talks About

EPCs were designed to make comparing homes simple.

You get a rating from A to G, and in theory, the higher the letter, the better the property performs.

Simple.

Except EPCs don’t actually measure the real-world performance of your heating system.

Instead, they rely heavily on modelling assumptions — particularly fuel prices and energy cost calculations.

Because gas is usually cheaper per unit of energy, homes heated with gas often score better.

Electricity costs more per unit, so homes using electric heating frequently score lower.

This happens even when electric systems themselves are highly efficient.

The result?

You can spend thousands upgrading insulation, replacing windows, installing solar panels, or switching heating systems — and still watch your EPC score stay flat or even fall.

Why This Actually Matters

For many homeowners, EPCs aren’t just paperwork sitting in a drawer.

They affect real decisions.

EPC ratings can influence:

* Property values

* Rental eligibility

* Mortgage products and green finance

* Access to grants and funding

When the rating system creates confusing signals, homeowners and installers can both end up making decisions based on incomplete information.

How Gas Ends Up Looking Better Than Electric

The core problem is simple.

Current EPC calculations place a strong emphasis on fuel costs.

That means:

**Cheaper fuel = better score**

Not:

**Cleaner heating = better score**

Fuel prices also move constantly.

This creates situations where a fossil-fuel boiler can achieve an excellent rating while an electric system delivering near-perfect efficiency at the point of use receives a mediocre one.

That’s not because electric heating is inefficient.

It’s because the scoring system prioritises economics over technology.

Why Reform Is Finally Happening.

The government has recognised the problem.

In a consultation on EPC reform, it admitted that the current approach — a single letter based heavily on fuel prices — doesn’t support the transition to clean heat.

The government has already recognised that the current system has problems.

Using a single headline rating based heavily on fuel prices doesn’t align particularly well with the move toward cleaner heating.

The proposed reforms aim to replace one overall score with four separate measurements:

Fabric Performance

How well your home retains heat.

Heating System Performance

How efficient and low-carbon your heating technology is.

Smart Readiness

How well your home works with technologies like batteries, EV charging, and flexible tariffs.

Energy Cost

What the home is likely to cost to run.

This approach gives homeowners a more complete picture instead of trying to squeeze everything into one letter.

What EPCs Should Really Show

If EPCs are supposed to help consumers make better decisions, they should show multiple factors side by side.

Ideally, every homeowner should be able to see:

**Cost** — what you’ll actually pay to run the home

**Carbon** — the emissions impact

**Consumption** — how much energy the property actually uses

Looking at all three together gives a much clearer picture than a single letter ever can.

What This Means If You Own Electric Heating

If your electric boiler or heat pump appears under-rated on your EPC, don’t assume something has gone wrong.

A lower EPC score doesn’t automatically mean:

* Higher bills

* Poor efficiency

* Bad technology

* A poor investment

Instead, look at:

* Your actual energy costs

* Comfort levels

* Energy consumption

* Carbon reductions

Those often tell a more useful story than the certificate itself.

What Installers Should Be Explaining

For installers, this is less of a problem and more of an opportunity.

Customers frequently assume a lower EPC letter means they made the wrong decision.

Helping explain:

* Why electric heating can still be highly efficient

* Why EPC calculations can be misleading

* What upcoming reforms are changing

…can help customers feel more confident about their investment.

The Bottom Line

Gas boilers may carry an A rating today.

That doesn’t automatically make them cleaner, smarter, or more future-proof.

Electric boilers and heat pumps can deliver extremely high efficiency while producing no emissions at the point of use.

EPC reform is coming.

Until then, remember:

**The letter on your certificate tells part of the story — not the whole story.**