September 09, 2025

A Building Energy Rating (BER) estimates your home’s energy efficiency on an A-G scale using a standardised method called DEAP.

Installing solar PV usually improves your home’s BER because the electricity you generate on site reduces your calculated primary usage and carbon emissions.

The size of that improvement depends on your system design and, critically, your home’s current fabric.

Some homes see a full-grade jump after installing solar panels, while others see a modest lift in the numerical indicators without a letter change.

1. What is a BER?

A BER is the energy “label” for homes in Ireland. It shows two key numbers:

• Primary Energy Use (kWh/m²/yr): how much upstream energy your home is calculated to use each year per square metre.

• CO₂ Emissions Indicator (kgCO₂/m²/yr): the associated carbon emissions.

These are converted into the familiar A-G scale (A1 being best) so buyers, tenants and lenders can compare homes. A BER must be produced by a registered assessor using the national DEAP methodology.

The Dwelling Energy Assessment Procedure (DEAP) is used by BER assessors to calculate the energy performance and carbon dioxide emissions of a home’s space heating, water heating, ventilation and lighting.

It reflects a standardised occupancy and typical weather, not your personal habits or last year’s bills.

2. How assessors calculate BER

Assessors input the features of your home into DEAP:

• Fabric: insulation levels in walls, roof, floors, window/door performance, airtightness.

• Ventilation: natural vents, extract fans, or mechanical ventilation with/without heat recovery.

• Systems: heating (boiler/heat pump), hot water, controls, lighting.

• Renewables: solar PV, solar thermal, heat pumps, etc.

DEAP runs a monthly energy balance to estimate the home’s delivered energy needs and converts this to primary energy and CO₂ based on nationally defined factors. Because usage is standardised, BER is a like-for-like comparison tool rather than a record of your actual bills.

3. Where Solar PV fits in the BER

Solar PV reduces your home’s calculated electricity demand by providing on-site generation. In DEAP:

• The PV array’s size (kWp), orientation, tilt, overshading, and system losses are used to estimate annual generation.

• That generation is credited first against on-site electricity use (lighting, pumps/fans, appliances and, in some homes, electric hot water or heating).

By needing less grid electricity, your primary energy and CO₂ indicators go down, often enough to lift the BER grade.

Two important clarifications:

• Exported electricity (units you don’t use and send to the grid) doesn’t improve the BER. BER rewards energy you avoid importing, not what you export.

• Batteries are excellent for self-consumption and resilience, but they typically don’t add extra BER credit beyond enabling more of your PV to be used on site. The certificate doesn’t give “points” for having a battery.

4. So, will PV improve my BER, and by how much?

The honest answer is: almost certainly yes, but the degree to which it improves will vary.

What makes the biggest difference?

1. Your current heating and hot water

• Homes using electricity for hot water or space heating tend to see greater BER improvements from solar PV, because solar PV directly offsets electricity use.

• Gas or oil heated homes still benefits, especially through lighting, pumps/fans and home appliances, just typically less per kWp.

2. System design and yield

• kWp size, roof orientation/tilt, shading, inverter efficiency, and cable losses determine your annual generation.

• Read this article to learn more about the importance of solar panel orientation.

3. Self-consumption

• The BER methodology credits PV that displaces on-site use. Daytime loads (e.g., hot-water diverters, heat-pump operation, appliances on timers) help translate kWh generated into kWh credited.

4. Your starting point

• Moving from a low C to a high C may take fewer indicator points than jumping from a solid C to a B3. Installing a solar PV system can tip you over a boundary or simply reduce the numbers within the same band.

5. Fabric and ventilation

• Good insulation, airtightness and efficient systems keep your calculated demand lower, so each kWh from solar has a cleaner path to improving the score.

6. Realistic expectation ranges

• 2–3 kWp on a typical semi-detached: noticeable reduction in indicators; sometimes a half to full-grade improvement if starting from a mid-C with decent fabric.

• 4–6 kWp on a detached home: often enough to shift a weak C towards B3/B2, particularly if paired with controls and some fabric upgrades.

• Small arrays (≤2 kWp) on terraced home: still helpful; the letter may not change, but the numbers usually improve.

These are directional, not promises. Your assessor can test your exact inputs in DEAP to see the likely outcome.

5. What doesn’t change (and common misconceptions)

Export payments: While export energy is great for your wallet, it Is irrelevant when it come to calculating your BER. BER only considers the energy you don’t need from the grid.

Batteries: Battery storage is extremely useful for self-consumption, however they don’t receive separate BER credit. Any benefits comes from enabling greater use of self-generated electricity.

Smart Controls: Only certain control functions count, and only as defined by DEAP inputs. A branded app alone doesn’t improve your BER.

We will explore how smart systems can help you make the most of solar PV in a future article.

Poor fabric: Solar PV can’t mask heavy heat losses. Insulation, airtightness and ventilation are remain foundational to a high BER.

6. How to maximise the BER impact of your PV

Design for yield and self-consumption

• Aim for the best roof orientation available (south-facing is ideal).

• Minimise shading and prioritise efficiency and durability with high quality products and installation.

• Consider a hot-water diverter and schedule appliances to run early in the morning to increase self-consumption.

Size the array correctly

• Bigger isn’t always better for BER if much is exported. Balance array size against your daytime loads (including any planned heat-pump/hot-water electrification).

• Pair with fabric-first upgrades

• If you’re close to a band boundary, small measures such as cavity fills and draft-proofing can help solar PV push you into the next grade.

Plan for future electrification

If you’re considering installing a heat pump in the future, solar becomes even more important in DEAP, as more of your home’s energy demand is electrical and can be offset by your array.

7. Documentation your assessor will need

Having the right paperwork helps the assessor model your system accurately:

• System details: total kWp, make/model, orientation and tilt for each roof plane, estimated overshading.

• Inverter: make/model, rated efficiency.

• Commissioning documentation: installation/commissioning date, test certificates.

• Site layout: panel layout drawing or photos can help confirm shading/orientation.

• Mains details: MPRN and address as on the certificate.

• Any control devices: diverter specifications if fitted.

If you’re planning on installing solar PV, your BER will need to be assessed following installation in order to claim the SEAI Home Solar Grant.

Read this article to learn more about the SEAI home solar grant and how to claim it.

8. Costs, Value and Resale

Estate agents and lenders increasingly use BER as a quick indication of the running costs and carbon profile of a home. While insulation and heating system upgrades remain the heavy hitters for BER movement, solar is often a cost-effective, low-disruption way to improve BER.

Even when the grade doesn’t change, a better primary energy/CO₂ number can still strengthen a listing and buyer confidence, backed up by real bill savings from self-consumed solar energy.

9. FAQs

Q: Will my BER definitely jump a full grade with PV?

A: There is no guarantee. Many homes do see a band improvement with a well-designed 3–6 kWp system, but some will simply see meaningfully better indicators within the same band. Your starting point and system design matter.

Q: Does a battery help my BER?

A: It may Indirectly help your BER. The BER doesn’t award separate credit for a battery, it only recognises PV generation that directly displaces grid imports. Batteries can help use more of your own self-generated electricity, which is what the BER rewards.

Q: Is exported electricity counted?

A: No. BER only accounts for self-generated solar electricity that offsets on-site consumption.

Q: What size PV should I pick for BER gains?</h3

A: As large as is sensible for your on-site daytime electricity usage and roof. Oversizing into heavy export improves bills less and doesn’t help BER much beyond the self-consumed portion.

Read this article to learn more about solar system sizing.

10. Next steps for homeowners in Ireland

Get a quick feasibility design showing kWp, expected yield, orientation/tilt and estimated self-consumption measures such as a hot water diverter.

Ask a registered BER assessor to run your home through DEAP with and without the proposed solar system to see the likely change.

If you’re close to a band threshold, combine solar with targeted fabric or controls to maximise the chance of a letter uplift.

11. Final Thoughts

Solar PV is one of the simplest ways to make a measurable dent in your home’s calculated energy use and CO₂ emissions, and your BER will usually show it. Treat solar as part of a whole-home plan (fabric, systems, smart self-consumption), and you’ll get the best of both worlds: stronger BER indicators and real-world bill savings.

Ready to Take the Next Step?

If you’re thinking about going solar, we can help make the process stress-free. Complete the form below to get a free home solar quote and consultation.