How to choose a standalone photovoltaic system for your home or vacation house
20/04/2026
Energy independence is no longer a luxury – it's an investment. With off-grid photovoltaic systems, you can have electricity anywhere without the need for a grid connection, whether it's for a permanent residence, a holiday home, or a caravan.
What is an off-grid photovoltaic system?
An off-grid photovoltaic system produces and stores electrical energy independently of the utility grid. It consists of four main parts:
- Photovoltaic panels — collect solar energy.
- Charge controller (MPPT or PWM) — ensures proper battery charging.
- Batteries (usually lithium) — store energy for use when there is no sun.
- Inverter — converts DC power to AC so you can use it normally with your appliances.
When is an off-grid system beneficial?
- In areas without a grid connection (mountains, islands, holiday homes).
- When you want energy independence from the utility.
- If you pay high fixed charges for low consumption.
- For use in caravans, boats, or isolated installations.
How to calculate the correct power
The choice depends on your daily consumption in Watt-hours (Wh). Calculation example:
| Appliance | Power (W) | Time (hours/day) | Consumption (Wh) |
|---|---|---|---|
| LED Lighting (5 bulbs) | 10 | 5 | 250 |
| Television | 60 | 3 | 180 |
| Small Refrigerator | 100 | 12 | 1200 |
| Router / Mobile charging | 20 | 8 | 160 |
| Total | 1790 Wh/day |
Equipment selection – what to look for
- Panels: Monocrystalline with high efficiency (>21%).
- Charge controller: MPPT for better energy utilization.
- Inverter: Pure sine wave, equal to or slightly greater than the maximum consumption.
- Batteries: Lithium (LiFePO₄) – last 3× longer and allow full discharge without damage.
Indicative cost and payback
| Use | Estimated Power | Cost (€) | Payback |
|---|---|---|---|
| Holiday home / caravan | 1–2 kW | €1,200–€2,000 | 3–4 years |
| Permanent residence | 3–5 kW | €3,500–€5,000 | 4–6 years |
Maintenance & longevity
Modern panels have a lifespan of 25+ years and batteries >10 years. Maintenance is limited to cleaning surfaces 2–3 times a year, checking cables and fuses, and updating the inverter's firmware.
Why Choose Hellenic Energy?
We install off-grid photovoltaic systems throughout Greece with Victron, Longi, and Pytes equipment. We offer free study and site inspection.
FAQ
Can I connect an off-grid photovoltaic system to the utility grid as well?
Yes, through a hybrid inverter, you can have both autonomy and grid connection.
What happens on days without sun?
Energy is stored in the batteries, which can cover 1-3 days of use depending on capacity.
Are there subsidies for off-grid systems?
The "Exoikonomo" program covers part of photovoltaic systems with storage – check the conditions each year.