How to Finance Solar During a Renovation or Extension

Adding solar to a renovation or extension can be funded in two main ways: (1) as part of a construction loan tied to your building contract, or (2) via an equity top‑up on your existing home loan (or a refinance with cash out). The best choice depends on your project size, how much equity you have, and how tightly you need to control cashflow and risk.

This guide gives you a decision‑grade comparison of construction loans versus equity top‑ups for solar, plus a one‑week action plan so you can move from “good idea” to “clear plan” this week.

Get clear on your renovation scope and solar costs before choosing a loan structure.

1. Start with the numbers: what does solar really cost?

Before you talk loan types, you need a realistic solar budget. Many people dramatically underestimate the cost of adding solar (and batteries) to a major renovation.

For current price ranges and how to interpret quotes, see the dedicated guide: What Solar System Really Costs You – And How Much To Borrow.

1.1 Typical solar and battery costs in 2026

Indicative (not a quote):

• 6–8 kW solar only: $6,000–$10,000
• 10–13 kW solar (larger homes, some three‑phase): $10,000–$18,000
• Battery (10–15 kWh): $9,000–$18,000
• Upgraded switchboard / wiring / monitoring: $1,500–$5,000
• Roof works (tilt frames, structural tweaks): highly variable, often part of the renovation contract

So a realistic bracket for “renovation‑grade” solar and battery is often $15,000–$35,000, and can push past $40,000 for large homes or complex roofs.

1.2 Rule of thumb: when solar is “big enough” to treat as part of the build

As a rough guide:

• Under ~$15,000 and not structurally complex: could sit outside the main construction loan as a simple equity top‑up or even be paid in cash.
• $15,000–$40,000 and/or dependent on roofing, wiring or structural works: worth seriously considering inside the building contract or as a clearly planned equity top‑up.
• $40,000+ or part of a major extension/rebuild: usually better integrated with the overall project finance and valuations.

2. Construction loan vs equity top‑up: the core idea

2.1 What is a construction loan for renovations and extensions?

A construction loan funds major works (extension, second storey, significant structural renovation) based on an approved building contract. Key features:

• The bank or lender approves a total facility limit based on the property’s “on‑completion” value.
• Money is released in progress payments to the builder (slab, frame, lock‑up, fit‑out, completion).
• You usually pay interest‑only during the build, then revert to principal and interest.

You’ll find more background around construction loans and large projects in Smart ways to fund major renovations and rebuilds in Rose Bay.

2.2 What is an equity top‑up?

An equity top‑up is an increase to your existing home loan (or a new split) using the extra value in your property as security. Key ideas:

• Lenders generally like your total loans to be ≤80% of property value to avoid LMI.
• If you do go above 80%, Lenders Mortgage Insurance can add thousands of dollars.
• You can structure a separate loan split for solar so you can track and potentially pay it down faster.

For a broader look at equity release for home works, see Using Home Equity for Renovations and Rebuilds in Sydney’s East.

2.3 The key difference for solar

• Construction loan route: solar is part of the building contract, paid via progress payments, and included in the end valuation.
• Equity top‑up route: solar is funded separately, either before, during or after the renovation, usually paid directly to the installer.

Neither is always “better”. The question is which one matches:

1. Your timeline (when you want solar installed).
2. Your equity position and borrowing capacity.
3. How much complexity and paperwork you can tolerate.
4. Your risk appetite around valuations and cost overruns.

3. When to use a construction loan for solar

3.1 Signs the construction loan is the right home for solar

Leaning towards a construction loan for solar makes sense when:

1. You’re already doing a big structural renovation or extension.
2. Your builder is happy to include solar as a prime cost (PC) item or a firm line item.
3. The solar install is integrated with roof works, electrical upgrade or battery room.
4. You want everything in one loan and are comfortable with progress payment rules.

3.2 Pros of including solar in the construction loan

• Single valuation, single approval. The valuer estimates the finished house with solar, which may support a higher “on‑completion” value.
• Interest‑only during build. You’re not making full repayments on the solar spend until completion.
• Cleaner builder coordination. The builder can schedule roof preparation, wiring and solar installer access.
• Potentially higher final value. A smart, integrated solar and battery system can be attractive in valuation reports, especially in energy‑conscious suburbs.

3.3 Cons and risks

• More lender scrutiny. Banks may want detailed quotes, product specs and timing.
• Less flexibility if you change your mind. Variations within construction loans can be slow and subject to re‑approval.
• Valuation and buffer risk. If the final valuation comes in low, your lender might reduce the facility — which can squeeze solar and other “non‑essential” items.
• Progress payment timing. Solar installers often want a big chunk of money on or just after install, which doesn’t always line up neatly with bank drawdowns.

3.4 Worked example: construction loan including solar

Imagine:

• Current home value: $1,600,000
• Existing loan: $900,000 (56% LVR)
• Renovation + extension building contract: $600,000, including $30,000 solar and battery

The lender orders a valuation and the valuer estimates on‑completion value of $2,200,000.

• Max lend at 80% LVR = 0.80 × $2,200,000 = $1,760,000
• Less existing loan: $900,000 → $860,000 capacity for construction costs and fees
• You only need $600,000 → the deal is very comfortable at around 69% LVR on completion.

In this scenario, including solar inside the construction loan is straightforward. You have:

• Plenty of equity buffer.
• One loan structure.
• Flexibility if the builder or solar quote creeps up.

Including solar inside a construction loan can work well on major extensions and rebuilds.