If you use your holiday home mainly in summer or for a few weekends, assessing a photovoltaic system requires more than an annual bill. The key question is how much of the electricity generated can be used when you are actually using the property.
This guide is for holiday homes connected to the electricity grid. If you are looking for complete energy independence for a property without a grid connection, a different assessment is needed, as we explain in our guide to off-grid photovoltaic systems.
Start with a calendar of how you use your holiday home
For each month, note how many days you stay at the house and how many people use it. Distinguish between an extended summer stay and short visits. Also record whether the property remains completely closed or hosts relatives while you are away.
Add the significant energy uses for each period: air conditioning, electric water heating, cooking, heating or car charging, if applicable. A future change in how the property is used is relevant to the assessment only if it is a specific plan. Do not count the entire winter as an occupancy period if you are still only considering that possibility.
This helps you avoid a common pitfall: choosing a system for the most demanding fortnight in August without considering what happens during the rest of the year.
Gather actual consumption data for each period
Use bills covering at least one full year. Prefer actual meter readings over estimates, and check the dates covered by each reading. If a bill covers several months, it does not by itself show how much electricity you used in each month.
- Record kilowatt-hours, not just the total amount paid.
- Match the billing periods to the days you stayed at the property.
- If you have detailed readings, keep a typical day of occupancy separate from a day when you are away.
- Note any exceptional consumption, such as renovation work, so it is not treated as an ongoing need.
If data is missing, ask for the assumptions used in the assessment to be stated clearly. An estimated usage profile can help compare options, but it should not be presented as a measurement of your own home.
Check what keeps running while you are away
A closed holiday home does not always have zero consumption. A refrigerator, alarm system, internet connection or specific property-care equipment may remain switched on. Record only what you actually use, and for how many hours.
This baseline load affects how much generation can be used while you are away. However, it is not a reason to run unnecessary appliances just to “use up the solar power.” Useful savings come from meeting actual needs.
Compare generation and consumption month by month
Ask for a generation estimate based on the specific location, tilt, orientation and shading of your roof. The European Commission’s PVGIS provides estimates of average monthly and annual generation for grid-connected photovoltaic systems without storage, based on long-term climate data. These are estimates, not a guarantee of generation in any particular year.
The monthly comparison shows when there may be a surplus. It is not enough to calculate direct self-consumption: even within the same month, generation may occur at times or on days when the house is empty. Ask for the analysis to examine this timing as well.
An illustrative example of seasonal use
For illustrative purposes only, let us assume a holiday home with annual consumption of 2.400 kWh: 1.800 kWh from June to September and 600 kWh during the other eight months. 75% of consumption is concentrated in four months. This is not an actual project or a generation forecast.
Even if a proposed installation is estimated to generate 2.400 kWh per year as well, equal annual totals do not prove that all needs will be met. It is necessary to assess how much energy is generated while you are staying at the house, how much you use at the same time, and how much is surplus while you are away.
Ask for a comparison of different system sizes, with and without a battery
Do not limit yourself to the largest installation that fits on the roof. Ask for at least two photovoltaic system sizes, using the same usage assumptions. For each one, the proposal should separately show direct use of the generated electricity, energy drawn from the grid and surplus.
If you are considering a battery, ask how much additional useful energy it will provide during the days you stay at the property and how it will be used when the house is closed. Home energy storage shifts energy between hours, within its available capacity. It should not be treated as a way to store the generation from one month for your next holiday.
Ask for the battery’s additional cost and benefit to be shown separately. For each financial scenario, it should also be clarified how the surplus is valued under the specific contract and what electricity purchase price is used. Do not assume that every kilowatt-hour generated automatically equals one kilowatt-hour that you will not purchase.
Plan for monitoring when the home is unoccupied
An extended absence makes remote monitoring of system operation useful. Check how the equipment will connect to the internet, whether the connection will remain active throughout the year, and who will receive any alerts. Available features depend on the equipment and service you choose.
Also agree on the process for communication and access to the property when a technical inspection is needed. You can find more about operating data in our guide to monitoring of photovoltaic systems.
What to have ready before requesting a study
- Bills and available meter readings for a full year.
- A month-by-month occupancy calendar and a list of devices that operate while you are away.
- Details about the location, roof, and existing electrical connection.
- Specific planned changes to how the property will be used.
- A request to compare system sizes and assess the battery separately.
At Solar Home, we review consumption data and available space before preparing a proposal. If you are planning photovoltaics for your holiday home, you can request an assessment, stating from the outset which months you use the property and how you use it.
Source and further documentation
European Commission, Joint Research Centre: PVGIS for grid-connected systems — capabilities and assumptions for estimating monthly production.
