Domestic heat pumps & solar - any advice?

[Malarky]

I'm starting to investigate an air heat pump and a limited number of solar panels (roof space is limited) and wondered if any friendly folk here had any experience or guidance (there is water involved). I think a lot of the advice online is fairly partial. A few of my initial observations and some dumb questions about what seems to be an expensive minefield:

• Ground heat pumps are out of the question requiring massive amounts of £££s, land space and works.
• Supplying solar power energy back to the grid? Is it better to use a diverter to use the power directly in your own house? Energy companys buy your units at half the cost they sell them to you. Plus I feel I want to avoid the whole Smart Meter set-up. What is the smartest thing to power from the solar and how does that work, can it 'top-up' supply from the mains across multiple appliances or is power just directed to one place?
• Battery storage of power from the solar - out of the question because too expensive?
• Heat pumps make noise - 40 to 60db. and need to be 1m away from property boundaries. This sounds pretty noisy.
• Can use with existing water filled rads but I'm concerned how warm these rads will ever become. How to solve this? How much gain is made by taking out existing older one panel rads and replacing with more modern alternative? (more cost).
• Immersion heater is still required to heat water for domestic use at about 50p per hour. Heat pump water is not hot enough to kill the bugs.
• Need to end all use of gas to avoid standing charge so best to switch to electric cooker hob (more cost).
• Our set up currently is gas boiler sending hot water to rads and a hot tank (first floor) for domestic use. What needs to change with a heat pump set-up? Our house is well insulated (loft and double glazing).
• I'm looking to be ahead cost wise over a number of years and to stop burning gas though not sure anyone can calculate this saving as cost of gas is so unpredictable.
• Current UK gov subsidy is £7.5k (scheme runs to 2028) so cost of the heat pump to me may be in the region of £5 - £7k. Are heat pumps likely to get cheaper, smaller, more efficient any time soon?

 

[Maf 2500]

The only people I know with an air heat pump hate it because it is loud enough to keep them awake at night. I think they had it moved further away from the house which was better but did not completely solve the problem. (They were doing a new build and could spec the increased diameter copper pipes and larger radiators needed for a heat pump, so that extra expense was not a concern.) Do not underestimate the disturbance to your household it will cause to rip up your floorboards to replace all the pipes running under there with thicker pipes, plus the cost involved.

The real question is how old is your gas boiler? If it is relatively new and relatively fuel efficient I would just run it until it becomes end of life, or obsolete because of new technology, by which time heat pumps will have improved in efficiency or there will be a shiny new tech that is even better. If your gas boiler is already very old and needs replacing consider whether the most efficient gas boilers available today are a better fit for your current situation in that you will not have to replace the existing copper pipework and radiators.

I really want to like heat pumps as a move away from fossil fuels is obviously a good thing, but as they stand today they are not the ideal solution for most people in terms of practicality and economics. Hopefully new technology will improve things in the next few years.

I haven't anything negative to say about solar, I will let others share their advice which I imagine will be positive. I think you can use the energy generated in your own home and only the surplus is sent back to the grid. The batteries for storage seem like a waste of money, waste of space and potential fire hazard.

 

[Little]

I have an old solar setup (several years old now).

The solar electric system often shows the house as zero energy use when the sun is out.
We don’t actually get paid accurately for energy we don’t use. Instead we get paid half of what the panels generate regardless of how much I did or did not use (FIT = Feed in tariff) So we try to make the most out of it by running what high energy things we need while the panels are getting full wack of the sun (dishwasher, washing machine, cooking etc…). On the topic of cooking, induction is really good.
Also, in the heatwave, the panels covered the air conditioning power draw. So free cooling.

Our solar heating system is harder to justify. In summer the water is scolding hot. In winter, if it’s sunny, you can feel some heat running into the tank but the main boiler definitely needs to do the bulk of the work.

I think there are a lot of options now and will continue to be released in the future.

 

[Wookii]

Can’t help with heat pumps, but I have solar system on my house and our business (a factory). Both are very good and we’ve seen a massive decrease in bills during the sunnier periods.

To answer your solar questions directly:

Supplying solar power energy back to the grid? Is it better to use a diverter to use the power directly in your own house? Energy companys buy your units at half the cost they sell them to you. Plus I feel I want to avoid the whole Smart Meter set-up. What is the smartest thing to power from the solar and how does that work, can it 'top-up' supply from the mains across multiple appliances or is power just directed to one place?

Yes you only receive a fraction of the unit price when supplying back to the grid, but in all honesty you need a large solar system for the average house to supply anything significant back to the grid.

Smart meters are easily installed and free. No reason not to want one.

Personally I would recommend adding battery storage if you can, this then allows you to store some excess electricity generated during the day, and use it at night, extending the contribution of your system.

Immersion heater is still required to heat water for domestic use at about 50p per hour. Heat pump water is not hot enough to kill the bugs.

You can utilise excess solar to heat water tanks during the day if the inverter system is smart enough to redirect the excess power for that purpose.

 

[Ehcosbie]

I have an ecodan heat pump and have had it circa ten years. The heatpump makes the most noise when it is heating the water over 40degrees. Hot water Cylinder holds the heat really well, so we programmed the hot water to only come on 06.00-07.00 and 16.00-17.00. Does my family of four fine with no issues. Immersion heater only used if demand is higher (visiting guests) than what the heatpump can handle, plus you can just turn it off. Heat pump has a weekly legionnaires cycle, we have it set at midday on a Wednesday while the world is out working ( this is the noisiest cycle, as it has to raise the water temperature to its highest level). The heat pump heats the house with underfloor heating not radiators. I hear radiators need to be massive as the water that goes through the heating system is about 35degrees from memory. We insulated the hell out of the house as we did a full renovation, floors walls and ceilings this has probably helped massively. Our house is entirely electric as no grid gas in our area, electric is about £160 per month.

Would I change it? No, it is set and forget, very easy. Service once a year, only issue we have had was with an expansion vessel. Had it swapped out, no other issues.

I hope this helps.

 

[Malarky]

Thanks everybody for v useful intell.

 

[Tim Harrison]

I've done various renovations over the years and took a deep dive in to air source heat pumps for the last one. I quickly came to the conclusion it'd only be efficient enough to justify the initial outlay in a passive type house. As @Ehcosbie above, and underfloor heating is needed to get the best out of them, since they run at around 40 degrees.

My wife's uncle installed a very expensive system in his house and it doesn't work very well. When her uncle isn't looking her aunty keeps the thermostat in the fridge to keep the house warm. Needless to say their electricity bill has gone through the roof. I heard a similar story from friends of a friend, their's has quadrupled.

As for solar, we had a large system installed, along with battery storage. Overall it's cut our bills by around 40% in winter and 100% in summer. During summer we pretty much feed back in to the grid constantly. We've found Octopus Energy gives the best tariff, atm it's 15p kw/h for customers. We estimate payback will be around 7-8 years, if the price of energy keeps rising accordingly. Most of our panels are south west facing obviously if they were all oriented south it's be much more efficient.