The short answer
Solar will not heat your rooms in January. What it will do on an oil-heated house is take over your hot water for a large part of the year, run the appliances that quietly eat electricity, and — with a battery — cover the evening. In practice that means fewer oil fills and a smaller electricity bill, not one or the other.
Roughly two-thirds of homes in Northern Ireland heat with oil, so this is the normal case here rather than the exception. It's most of what we survey outside Belfast.
Where the oil actually goes
An oil boiler does two jobs: space heating and hot water. Through the coldest months, space heating dominates and solar can't touch it — the panels are producing least exactly when the house wants most. But from roughly March to October the boiler is often firing only to heat a cylinder of water, and that is the job solar can take.
That's the swap worth understanding: every time the immersion heats the cylinder on surplus solar, the boiler doesn't fire, and you don't burn oil to do it.
The three pieces, in the order they earn their keep
- The array. Sized to your usage, not your roof. Daytime electricity — fridge, freezer, oven, kettle, washing, the office — comes off your own roof first.
- A hot-water diverter. A myenergi eddi watches for surplus and modulates it into the immersion instead of exporting it at 9.64p. This is the piece that displaces oil, and it's usually the cheapest of the three.
- A battery. Carries the evening — the hours an oil-heated house is busiest and the panels are done. It can also charge overnight on a cheap rate. Solar plus battery starts at £6,750 installed; see battery storage.
The order matters. On an oil-heated house with a cylinder, a diverter tends to give the most obvious result for the least money, because you can watch the boiler stop firing.
What it doesn't do
Straight answers, since this is where people get oversold:
- It won't replace your boiler. You still need heat in winter, and solar in December produces a fraction of June.
- A diverter needs a cylinder with an immersion. Combi boiler with no tank, no diverter — the eddi has nothing to heat. It can be pointed at storage heaters or underfloor instead where those exist.
- It won't heat the cylinder on a wet January day. There simply isn't the surplus. The gain is spread across roughly seven or eight months of the year.
- It isn't a heat pump. If your plan is to get off oil entirely, that's a different conversation — though solar and a battery make a heat pump cheaper to run when it comes.
Why the rural NI case is often stronger than the Belfast one
Bigger roofs, more outbuildings, more space for a battery, and usually no conservation-area complications. Rural properties are also the ones that lose power in a storm, which is where backup power earns its place — a battery configured for backup keeps the freezer, the router and the lights on when the line comes down.
One rural caveat: on single-phase rural supplies NIE Networks sometimes sets an export limit. That caps what you can push to the grid, not what you generate and use — and it makes a diverter and a battery more valuable, not less, because keeping the energy at home is the point.
How we work it out
At the survey we look at the roof, the cylinder and the board, and model your generation against your actual electricity use and your oil pattern. You get a fixed written quote and a straight answer — including "not worth it" when a north-facing roof or a combi-only house says so. Solar panels has the packages, or call 028 9691 8755.
Questions people ask
Will solar panels heat my house if I have oil heating?
No — solar produces electricity, not heat, and produces least in the coldest months. What it does is cover your hot water for much of the year through a diverter, plus your daytime electricity, so the boiler fires less and you buy less oil.
Do I need a hot water cylinder for a solar diverter?
Yes, or another resistive load. A myenergi eddi sends surplus to an immersion heater in a cylinder, or to storage heaters, underfloor heating or electric heaters. With a combi boiler and no tank there is nothing for it to heat.
How many months of the year would solar cover my hot water?
Broadly the warmer half to two-thirds of the year, depending on your roof, your array size and how much water the house uses. Deep winter always needs the boiler. We model it from your own roof at survey rather than quoting an average.
Is a battery worth it on an oil-heated house?
Often more so, because oil-heated houses tend to be rural, use electricity in the evening and lose power in storms. A battery carries the evening on daytime solar, can charge on a cheap overnight rate, and can be configured to keep essentials running in a cut.