Energy savings simulator
Explore what changes in your building, one intervention at a time.
Illustrative examples, not measured Greek averages or an energy study. Every default is an editable assumption. Enter investment costs from your own quotation.
Your scenario configuration
One consistent baseline for every solution
Individual interventions are compared with today’s building. The combined scenario recalculates loads rather than adding saving percentages.
| Scenario | Grid electricity kWh/year | Fuel kWh/year | Purchased energy reduction | Energy cost €/year | Gross savings €/year |
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Combined energy balance
4. Investment & simple payback
Optional amounts from actual quotations. No market prices have been inserted. Zero additional annual cost is an assumption to verify. Enter a separate package quotation for the combined scenario to avoid double-counting overlapping work. After changing material, thickness, roof area or battery, update the corresponding cost quotation before assessing payback and financing.
| Scenario | Investment before grant € | Additional annual cost € | Net savings €/year | Payback before grant/loan |
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5. Grant & borrowing
Set financing separately for each intervention. These are your assumptions, not a grant approval or bank offer.
Assumption: the grant is received at the start. No bridging finance for delayed disbursement is modelled. The loan uses fixed interest and equal monthly payments, starting one month after disbursement, with no grace period or balloon payment. Fees are paid upfront from own funds. The interest rate is not APR. Insurance and other recurring charges are excluded.
A grant reduces investment; borrowing changes own funds and cash flows, not energy savings. Negative cash benefit means additional annual outflow. Total owner payments do not deduct operating savings. Values are nominal, without discounting.
Annual repayment schedule
| Year | Payments € | Interest € | Principal € | Loan balance € | Benefit after payments € |
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Financing comparison across interventions
| Intervention | Grant € | Loan € | Own funds € | Payment €/month | Year-one cash benefit € |
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CFPB — How payments are split between principal and interest
Method & model limitations
Useful heating = area × annual specific heat demand. Fuel or heating electricity = useful heat / seasonal efficiency. Cooling is calculated similarly. Auxiliary consumption is included only if reflected in seasonal performance or other electricity use.
Added insulation resistance R = thickness in metres / λ. New U = 1 / (1 / old U + R). Relative U reduction is multiplied by wall coverage and the wall share of heating or cooling demand. This is a screening approximation without thermal bridges, solar gains, moisture or dynamic cooling calculations. Controls are then applied sequentially.
Panel count = floor(usable roof / required area per panel). Capacity kWp = panels × Wp / 1,000. Generation = kWp × annual specific yield. Replace layout assumptions with a design and yield with PVGIS results for location, tilt, orientation and losses. There is no live PVGIS connection.
Direct consumption is capped by demand. Battery charging is limited by surplus, capacity × cycles and remaining demand. Storage losses are deducted. This is not hourly dispatch and cannot establish time matching, backup autonomy or actual self-consumption.
Purchased energy combines grid electricity and fuel input in final-energy kWh, not primary energy. PV replaces purchased energy; it does not directly lower building loads. Batteries shift consumption and incur losses.
Detailed mode adds transmission, distribution, ETMEAR, PSO, fixed charges and any entered additional amounts/VAT. All-in mode uses only the entered variable bill price. ERT, municipal fees and property tax are excluded. Fuel uses its separately entered €/kWh price, with its applicable variable charges already included. Price changes, discounting, replacements, degradation and domestic hot water are not modelled.
No geographic adjustment is applied automatically. For a different climate, envelope or schedule, change specific demand using an engineering study or calibration against bills. Comfort is held constant before and after.
EPS 100 Graphite Plus uses λ = 0.030 W/(m·K) from declaration VN100 (Graphite Plus ECO6). The general 2026 catalogue lists a different value; confirm the declaration for the product in your quotation.
PSO tiers charge only the excess in each band. Annual use is allocated uniformly for illustration. Multiple meters are treated as equivalent and do not replace individual meter assessment. Agreed capacity and fixed charges remain unchanged even with zero grid imports. PV is not assumed to reduce capacity charges automatically.
Methodological references
Sources explain the physical principles and required inputs. They do not validate the GEBS numerical defaults or guarantee results.
- Vitextherm — EPS 80 White / Graphite
- Vitex 2026 — EPS 100 White
- Vitextherm — EPS 100 Graphite Plus · DoP VN100 · λ 0.030 W/(m·K)
- European Commission / JRC — PVGIS
- US Department of Energy — Heat Pump Systems
- US Department of Energy — Insulation Fact Sheet
- KNX Association — Energy management
GEBS · Annual screening model v1.3.0 · 01/10/2026