Energy renovation ROI: calculation and method (2026)

Clarify ROI in energy renovation: what you need to measure in 2026

Distinguish total cost, payback time and net gain over the years

To manage your ROI, separate three concepts. The total cost includes the studies, the works, maintenance and above all the remaining cost after MaPrimeRénov' and CEE. Payback time answers a simple question: how many years it takes for your savings to cover the investment. Net gain, meanwhile, looks at the total saved over 10 or 15 years, minus maintenance costs and replacements.

Identify the items that weigh the most: heating, insulation, ventilation, hot water

Start by measuring what actually consumes energy before the works. In most homes, heating remains the main item, followed by hot water. Insulation acts like a coat: it durably lowers needs. Ventilation prevents humidity and protects the gains, especially after reinforced insulation.

Set your calculation horizon: 5, 10, 15 years depending on the type of project

In 2026, choose a horizon consistent with the equipment's lifespan. 5 years for a settings adjustment, a thermostat, a small heat pump. 10 years for a balanced package of works. 15 years for the envelope — walls, lofts, windows. Keep the price of energy in mind: it's what ultimately shapes the result. To go further, set up consumption monitoring after renovation to verify the savings actually achieved.

Cost the investment accurately: every cost to include

Include materials, labour, studies, and ancillary costs (removal, scaffolding, finishing work)

For an all-inclusive costing, add up materials, labour and studies. Also think of the ancillary costs that are often forgotten: removal and waste disposal, scaffolding rental, protection, drilling, patching and finishing touch-ups, electrical or hydraulic connections, compliance work and inspections.

Anticipate contingencies: safety margin, price variations, unforeseen site issues

On a job site, not everything is visible at first glance. Plan a safety margin (often 5 to 10%) for surprises: hidden moisture, degraded substrates, thermal bridges, difficult access. Also frame material price variations with a quote validity period and by tracking building cost indices.

Account for maintenance: upkeep, replacement, warranties

A good budget includes life after the works: upkeep (e.g. heating and ventilation equipment), small replacements (filters, circulators, control components), and warranties — perfect completion (1 year), biennial (2 years), decennial (10 years). This is what protects your real ROI and prevents an energy saving from turning into an unexpected bill.

Estimate energy savings credibly and usably

Start from a baseline: bills, usage, floor area, existing insulation quality

Before promising gains, establish a reliable picture of the existing situation. Gather 12 to 24 months of bills, the heated floor area, the setpoints, occupancy schedules, the type of ventilation, and what is already insulated (lofts, walls, floors, windows). If possible, also record the equipment's power ratings and ages.

• Bills in kWh and euros, summer and winter alike
• Main uses: heating, domestic hot water, cooking
• Visible weak points: air leaks, thermal bridges, humidity

Translate the gains into euros: kWh saved, energy price, cautious scenarios

Convert the kWh saved into euros using a cautious scenario. In 2026, tariffs may fluctuate. Offer at least two price assumptions (low and high) and state clearly what's included. You get an ROI that's readable, and above all comparable between solutions.

Check consistency with reality on site: settings, behaviour, commissioning

An estimate only holds if the installation follows through. Check ventilation airflow rates, heating-curve settings, balancing, and commissioning (heat pump, mechanical ventilation, controls). Also confirm the expected occupant habits: target temperature, airing, programming. Otherwise, the savings stay on paper only. To frame the checks to plan for, rely on these essential checks.

Calculate the ROI step by step: method, formulas and worked examples

Apply the useful formulas: ROI %, simple payback time, discounted payback time

Start by costing the project, then the annual savings. ROI formula: ROI % = (net gain / net investment) × 100. Simple payback time = net investment / annual savings. Example: €12 invested, €10 saved. Simple payback: 12 years. For the discounted payback, apply a rate (e.g. 3%), since €10 tomorrow is worth less than €10 today.

Factor subsidies into the calculation: MaPrimeRénov', CEE and remaining cost

Work from the remaining cost. Net investment = quote including tax minus MaPrimeRénov' and the CEE bonus, based on the scales in force in 2026 and your client's situation. Keep a separate line for ancillary costs (connection, flushing, ventilation) to avoid an overstated ROI.

Compare several solutions: insulation alone, heat pump, hybrid, phased renovation

Put 3 to 4 scenarios side by side: insulation, heat pump, hybrid, phased. Compare net cost, savings, maintenance, summer and winter comfort. Insulation often delivers more consistent gains. A heat pump depends more on settings and the price of electricity. Choose the scenario with the best controlled risk, not just the shortest payback.

Optimise the profitability of your projects: concrete levers to improve ROI

Target the right packages of works: prioritise the envelope before the system

For a solid ROI, start with the envelope: loft and wall insulation, thermal bridge treatment, airtightness, then suitably sized ventilation. A less "leaky" home lets you size a heat pump or boiler more accurately, with lower consumption, fewer callbacks, and better client satisfaction.

Reduce the remaining cost: structuring the subsidies, supporting documents, RGE compliance

From the quote stage, secure the MaPrimeRénov', CEE, reduced 5.5% VAT and, if needed, zero-interest eco-loan arrangements. Prepare the key documents: detailed quotes and invoices, technical data sheets, RGE proof in the right scope, completion dates, declared floor areas and performance figures. A clean file avoids come-backs, speeds up payments and protects your margin.

Highlight the indirect benefits: comfort, property value, fewer breakdowns

Don't just sell kWh. Sell lasting comfort: a more stable temperature in summer and winter alike, less humidity, fewer breakdowns thanks to a less strained system, and often a higher property value through a better energy rating. In 2026, these arguments make the difference when the budget is being discussed.