ᐅ Is it possible for one house to supply two additional houses?

Good day to everyone reading!

The trend in Europe is clearly moving towards climate protection and reducing CO2 emissions. Currently, my house and my parents’ house are still heated with oil. I moved into my house in 2000, and my parents’ house is almost 100 years old; its heating system was replaced ten years ago. My house is quite well insulated, and I use about nine liters per square meter per year for heating and hot water. My parents’ consumption is only slightly higher because the house was built with a double-layer wall nearly 100 years ago. Further insulation improvements are hardly feasible since that would likely require renewing the roof structure.

There is a theoretical possibility to build a third house on the property in the coming years. Ideally, I would like to find a solution that completely eliminates burning oil or gas, for example by operating a ground-source heat pump powered by photovoltaic panels. Since the roof design of the two existing houses is not suitable for photovoltaic or solar thermal systems, I am currently wondering if it would be possible to plan and build the third house in a way that it could also supply the two older houses.

Ultimately, I would like a future-proof solution because I aim to live in the third house at some point and support myself with the rental income from the two front houses. In ten years, it will hardly be acceptable to have an oil delivery truck come once a year…

Is this realistic, or completely hopeless?

Matthias

You can install a ground source heat pump in the third house to also supply the other two houses.

Photovoltaics are a bit more complicated. Why are the roofs not suitable? Photovoltaic systems typically work by using the feed-in tariff in summer to cover the electricity costs for the pump in winter. Using photovoltaic electricity to heat the houses in winter is not feasible with that level of consumption.

With only one heat pump, all three houses should require similar supply temperatures; otherwise, at least one will operate with a lower efficiency than necessary.

For rental properties, I would recommend separate and simple heating systems to ensure the hygiene of domestic hot water heating and to manage the unpredictable heating habits in rental units.

So, a large heating system versus three smaller systems?
How far apart are the houses?

I can't say whether it’s cost-effective, but I fully agree with boxandroof’s point about renting, and I would rather recommend keeping everything separate. Who pays for what if something breaks? What happens if, for example, the parents’ house is eventually sold or rented out?

I don’t think it will ever come to selling individual houses separately since they all share a common driveway. The two existing houses are about 20 meters (65 feet) apart from center to center, and the center of the new third house to be built would be roughly 50 meters (165 feet) away from the centers of the two front houses.

By the way, the two existing houses do not have underfloor heating but use conventional radiators. I’m not entirely sure about the supply temperatures yet; I still need to check that. For the new house, I would probably use wall heating on the exterior walls.

What alternatives are there at all if we want to improve the existing houses? The roof surfaces are quite fragmented because of dormers, so there is hardly any space for photovoltaic or solar thermal systems. That wouldn’t be an issue with the new house, of course.

I’m also not completely sure if the concept of “producing electricity in summer and buying it during winter” really works, because if everyone does that, there would be an oversupply in summer and a shortage in winter.

Matthias

Pianist schrieb:

What alternatives are there if you want to improve the existing houses? The roof surfaces are quite broken up by dormers, so there is hardly any space for photovoltaics or solar thermal systems. That wouldn’t be a problem with the new house, of course.

I would avoid solar thermal systems as they are uneconomical and add complexity. Photovoltaics usually work better than expected, even on dormers.

Pianist schrieb:

By the way, the two existing houses don’t have underfloor heating, just standard radiators.

That argues against a heat pump, and even more so against a shared heat pump, since the old houses would also drag down the new one’s heat pump efficiency.

You would have to upgrade the insulation and heating surfaces of the old houses to get close to the new house’s performance. I don’t think that’s really practical. Is a gas connection possible? Otherwise, you’d have to continue with oil or use separate heat pumps which can then run with different efficiencies and flow temperatures.

Pianist schrieb:

Whether the principle “produce electricity in summer and buy it in winter” works, since if everyone does that, we’d have a surplus in summer and shortage in winter.

That was probably meant purely financially, not ecologically or practically. Financially, that’s how it is due to subsidies, since buying and selling electricity in winter/summer is currently not differentiated.

I would simply consider photovoltaics independently of the heating system, even though a heat pump can benefit somewhat from photovoltaics.